There is absolutely no doubt that physical activity is a beautiful phenomenon. In the above study, the study is fair to the extent that those subjects who regularly exercised had lesser hospitalisations. Here both reason and effect exist, but can a direct causal relationship be established between the two?
Can it be inferred beyond doubt that "the vaccine prevented complications of Covid-19 because exercise strengthened the immune response? The possibility of such a remarkable effect in the short term is pretty unlikely. And all the more, such findings can't be generalised to a larger population.
Authors seem to be ignoring a hidden confounder affecting the validity of the study, and this confounder is 'frailty'. Simply those doing less exercise were unable to do so because they were frail. And obviously, frailty can be present independent of comorbidities like DM, heart failure or obesity, which were evenly matched between the high and low-exercise groups.
So, the correct conclusions will likely differ if this confounder is considered. one may not forget that 'Correlation, even if present in a statistically significant portion, may not amount to causation.
The study might prompt some frail people or even morbidly obese people to engage in heavy exercise soon after the vaccination despite muscle aches and fever (common side effects of the Covid-19 vaccines). And these might have disastrous consequences. So the wo...
There is absolutely no doubt that physical activity is a beautiful phenomenon. In the above study, the study is fair to the extent that those subjects who regularly exercised had lesser hospitalisations. Here both reason and effect exist, but can a direct causal relationship be established between the two?
Can it be inferred beyond doubt that "the vaccine prevented complications of Covid-19 because exercise strengthened the immune response? The possibility of such a remarkable effect in the short term is pretty unlikely. And all the more, such findings can't be generalised to a larger population.
Authors seem to be ignoring a hidden confounder affecting the validity of the study, and this confounder is 'frailty'. Simply those doing less exercise were unable to do so because they were frail. And obviously, frailty can be present independent of comorbidities like DM, heart failure or obesity, which were evenly matched between the high and low-exercise groups.
So, the correct conclusions will likely differ if this confounder is considered. one may not forget that 'Correlation, even if present in a statistically significant portion, may not amount to causation.
The study might prompt some frail people or even morbidly obese people to engage in heavy exercise soon after the vaccination despite muscle aches and fever (common side effects of the Covid-19 vaccines). And these might have disastrous consequences. So the words of caution need to be stressed.
Nevertheless, the role of exercise in a healthy population should not be undermined.
Anne Benjaminse,1,2 Alli Gokeler3, 4, 5
1 University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, Netherlands
2 School of Sport Studies, Hanze University Groningen, Groningen, the Netherlands
3 Exercise Science and Neuroscience, Department Exercise & Health, Faculty of Science, Paderborn University, Paderborn, Germany
4 Amsterdam Collaboration for Health and Safety in Sports, Department of Public and Occupational Health, Amsterdam Movement Sciences, VU University Medical Center, Amsterdam, The Netherlands.
5 OCON Center of Orthopaedic Surgery and Sports Medicine, Hengelo, The Netherlands
Dear Editor,
We read the recent manuscript by Kal et al.1 ‘Explicit motor learning interventions are still relevant for ACL injury rehabilitation: do not put all your eggs in the implicit basket‘ with great interest. The authors did a commendable job summarizing the current literature and we highly respect them for being critical, to foster academic discussions to move science forward. We do however have some concerns regarding the methodology and interpretations made by the authors.
Confusing definition: description vs. execution First, the authors write: "Elite athletes have shown to successfully use explicit interventions to de-automate, and subsequently improve, problematic movements.“.2 The paper by Toner et al. is largely based on assumptions, case studies and philosop...
Anne Benjaminse,1,2 Alli Gokeler3, 4, 5
1 University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, Netherlands
2 School of Sport Studies, Hanze University Groningen, Groningen, the Netherlands
3 Exercise Science and Neuroscience, Department Exercise & Health, Faculty of Science, Paderborn University, Paderborn, Germany
4 Amsterdam Collaboration for Health and Safety in Sports, Department of Public and Occupational Health, Amsterdam Movement Sciences, VU University Medical Center, Amsterdam, The Netherlands.
5 OCON Center of Orthopaedic Surgery and Sports Medicine, Hengelo, The Netherlands
Dear Editor,
We read the recent manuscript by Kal et al.1 ‘Explicit motor learning interventions are still relevant for ACL injury rehabilitation: do not put all your eggs in the implicit basket‘ with great interest. The authors did a commendable job summarizing the current literature and we highly respect them for being critical, to foster academic discussions to move science forward. We do however have some concerns regarding the methodology and interpretations made by the authors.
Confusing definition: description vs. execution First, the authors write: "Elite athletes have shown to successfully use explicit interventions to de-automate, and subsequently improve, problematic movements.“.2 The paper by Toner et al. is largely based on assumptions, case studies and philosophers' views.2 The authors presume that with adopting explicit learning, patients are not allowed to know the goal of the exercises.3 For clarity, the correct definition of attentional focus needs to be used: Attentional focus relates closely to what you tell your patient prior to the execution of the exercise. An internal focus would be induced to focus the attention on body parts and movements. Conversely, for an external focus, the attention is directed to the outcome or the goal of the movement. Hence, adopting an external focus is related to the planning of the movement, but has nothing to do with the processing of intrinsic feedback or bodily awareness.4 It does not mean that patients are not aware of their body movements, i.e. the ‘explicit interventions’ the authors refer to. It is important to note that bodily awareness is not necessarily inherent to an internal focus of attention.5 Leaning is not possible without bodily awareness.6 An external focus of attention simply means the patient is focusing on the intended movement effect – while preparing for the execution.6 This does not mean that one must never use body related instructions that elicit an internal focus of attention. Of course you can use it. It will just not result in most optimal motor learning.7,8 In summary, it is important to differentiate between telling the goal of the exercise (i.e. description - general instruction) and the specific instruction provided just before the execution of the task. For example, in case of rehabilitation after ACLR: “the goal of this exercise is to improve knee bending while landing, as this promotes a softer landing, which is better for your knee.” Then, as the patient is preparing to execute the exercise, it is critical to shift their attentional focus that corresponds closest to the task goal: e.g. “focus on landing with as little noise as possible”.
Familiarity Second, the million-dollar question, do effects of implicit learning depend on the person’s preference? Here, again, the entire picture needs to be presented. Kal et al. conclude “Implicit or explicit learning appears most effective when it is aligned with an individual’s preference“, even though the original authors state: “Due to the well-documented external focus advantage we are hesitant to argue that direction of attentional focus does not have any influence on skilled motor performance.”.9 The preferred focus, often as a result of past experience with coaching instructions,10 is not always the most beneficial solution.11-15 In addition, retention, a key aspect of motor learning, has not been reported.9 It is thus not possible, and it may give a skewed representation, to conclude learning is most effective when aligned with an individual’s preference, as the definition of learning is ‘a relative permanent change in a person’s capability to perform a skill’.16 To interpret results, the authors need to adhere to the correct definition of motor learning. Directly observable performance improvement is different from sustained improvements over time (retention).16 Often times explicit learning is indicated as being effective, potentially because it shows quick benefits.17 The authors also write: “People with musculoskeletal conditions strongly prefer to consciously control movements.” But again, we need to ask the question if this preference is of benefit to them? Kal et al. should also have stated the conclusion of the paper they refer to: knee pain was more commonly reported by people with a propensity for conscious involvement in their movements.18 Thus, even it is the case that patients prefer to consciously control movements, it is not per se most effective.19 Loss of function, pain, fear of reinjury and other psychological factors, cause a shift in attentional focus towards the injured area such as the knee.19-22 The process behind this needs to be explored in further detail before we can say whether it is beneficial to consciously control movements. After musculoskeletal injuries neuroplastic changes of the central nervous system occur,23 which induces a focus on the injured joint. An ACL injury triggers neurocognitive disruption,23 demonstrating potentially maladaptive neuroplasticity within the brain whereby (pre)motor cortex areas are more active during simple movement tasks compared to uninjured individuals.24 Concluding, it would be unwise to leave patients to their own focus preference or assume they will find the focus that is optimal for them. Verbal and visual feedback The authors pose that explicit verbal feedback on movement has been identified as a key active ingredient in primary ACL injury risk reduction.25 However, again correct interpretation of scientific studies is crucial here. All these training programs are conducted in a relatively controlled setting (e.g. with supervision from researcher) with no retention and transfer effects measured.25 Also, no studies thus far have comparison included with implicit verbal feedback conditions. The authors also state that it is unclear whether improved biomechanics can be attributed to implicit learning per se as this can not proven through self-report.26 Indeed, self-report, although done often,27-29 is not the best way to provide objective evidence.30 But, it is widely known that model learning, as we did in this study,26 or observing and imitating movements facilitates an athletes’ exploration and search for their own most optimal functional task solutions,34-36is part of an implicit learning strategy.34 Studies using Electroencephalography and Transcranial Magnetic Stimulation conclude that movement outcome and efficiency are enhanced when an external focus of attention is promoted, 31-33, likely due to improved neural strategies, such as cortical inhibition.. When providing sound designed research with only the attentional focus instruction being different across groups, including a control group, one can conclude that difference across groups is based on that factor. Vice versa, how can we know athletes in previous research have indeed adopted an internal focus of attention? In sum, we feel the authors should have presented the entire picture to the readers based on sound synthesis of the literature and proper use of definitions.
REFERENCES
1. Kal E, Ellmers T, Diekfuss J, et al. Explicit motor learning interventions are still relevant for ACL injury rehabilitation: do not put all your eggs in the implicit basket! Br J Sports Med 2021.
2. Toner J, Moran A. Exploring the orthogonal relationship between controlled and automated processes in skilled action. Rev Philos Psychol 2020;1–17.
3 Toner J, Moran A. Enhancing performance proficiency at the expert level: considering the role of “somaesthetic awareness. Psychol Sport Exerc 2015, 16, 110e117.
4. Wulf G, Why did Tiger Woods shoot 82? A commentary on Toner and Moran. Psychol Sport Exerc 2016;337-8.
5. Milley KR, Ouellette GP. Putting attention on the spot in coaching: shifting to an external focus of attention with imagery techniques to improve basketball free-throw shooting performance. Front Psychol 2021;16:12.
6. Wulf G. An external focus of attention is a conditio sine qua non for athletes: a response to Carson, Collins, and Toner (2015). J Sports Sci 2016;34:1293-5.
7. Ille A, Selin I, Do MC, Thon B. Attentional focus effects on sprint start performance as a function of skill level. J Sports Sci 2013;31:1705-12.
8. Winkelman NC, Clark KP, Ryan LJ. Experience level influences the effect of attentional focus on sprint performance. Hum Mov Sci 2017;52:84-95.
9. Maurer H, Munzert J. Influence of attentional focus on skilled motor performance: performance decrement under unfamiliar focus conditions. Hum Mov Sci 2013;32:730–40.
10. Porter JM, Wu WFW, Partridge JA. Focus of attention and verbal instructions: Strategies of elite track and field coaches and athletes. Sport Sci Rev 2010;19:199–211.
11. Guss-West C, Wulf G. Attentional focus in classical ballet: a survey of professional dancers. J Dance Med Sci 2016;20:23-9.
12. Stoate I, Wulf G. Does the attentional focus adopted by swimmers affect their performance? Int J Sports Sci Coach 2011;6:99–108.
13. Abdollahipour R, Wulf G, Psotta R, et al. Performance of gymnastics skill benefits from an external focus of attention. J Sports Sci 2015;33:1807–13.
14. LoSarah L, Jagodinsky A, Torry M, et al. Effects of attentional focus cues on lower extremity kinematics during inside of the foot soccer trap among expert soccer players. Int J Sports Sci Coach. 2021;
15. Maloney MA, Gorman AD. Skilled swimmers maintain performance stability under changing attentional focus constraints. Hum Mov Sci 2021;77:102789.
16. Schmidt RAWC. Motor learning and performance. Champaign: Human Kinetics; 2005.
17. Masters R. Knowledge, knerves and know-how: The role of explicit versus implicit knowledge in the breakdown of a complex motor skill under pressure. Br J Psychol 2011;83:343-58.
18. Selfe J, Dey P, Richards J, et al. Do people who consciously attend to their movements have more self-reported knee pain? An exploratory cross-sectional study. Clin Rehabil 2015;29:95-100.
19. Gray R. Differences in attentional focus associated with recovery from sports injury: Does injury induce an internal focus? J Sport Exerc Psychol 2015;37:607-16.
20. Hsu CJ, Meierbachtol A, George SZ, et al. Fear of reinjury in athletes: implications for rehabilitation. Sports Health 2017;9(2):162–167.
21. Ardern CL, Taylor NF, Feller JA, et al. Psychological responses matter in returning to preinjury level of sport after anterior cruciate ligament reconstruction surgery. Am J Sports Med 2013;41:1549-1558.
22. Podlog L, Dimmock J, Miller J. A review of return to sport concerns following injury rehabilitation: practitioner strategies for enhancing recovery outcomes. Phys Ther Sport 2011;12:36-42.
23. Grooms D, Appelbaum G, Onate J. Neuroplasticity following anterior cruciate ligament injury: a framework for visual-motor training approaches in rehabilitation. J Orthop Sports Phys Ther 2015;45(5):381-93.
24. Needle AR, Lepley AS, Grooms DR. Central nervous system adaptation after ligamentous injury: a summary of theories, evidence, and clinical interpretation. Sports Med 2017;47:1271–88.
25. Sugimoto D, Myer GD, Barber Foss KD, et al. Critical components of neuromuscular training to reduce ACL injury risk in female athletes: meta-regression analysis. Br J Sports Med 2016;50:1259–66.
26. Welling W, Benjaminse A, Gokeler A, et al. Enhanced retention of drop vertical jump landing technique: a randomized controlled trial. Hum Mov Sci 2016;45:84–95.
27. Ruocco AC, Direkoglu E. Delineating the contributions of sustained attention and working memory to individual differences in mindfulness. Person Ind Diff 2013;54,226–30.
28. Scheibner HJ, Bogler C, Gleich T, et al. Internal and external attention and the default mode network. Neuroimage 2017;48:381-89.
29. Porter JM, Nolan RP, Ostrowski EJ, et al. Directing attention externally enhances agility performance: a qualitative and quantitative analysis of the efficacy of using verbal instructions to focus attention. Front Psychol 2010;1:216.
30. Zhou ZW, Lan XQ, Fang YT, et al. The inter-regional connectivity within the default mode network during the attentional processes of internal focus and external focus: An fMRI study of continuous finger force feedback. Front Psychol 2019;10:2198.
31. Mak TCT, Young WR, Wong TWL. Conscious control of gait increases with task difficulty and can be mitigated by external focus instruction. Exp Aging Res 2021;47:288-301.
32. Suzuki LY, Meehan SK. Attention focus modulates afferent input to motor cortex during skilled action. Hum Mov Sci 2020;74:102716.
33. Kuhn YA, Keller M, Ruffieux J, et al. Adopting an external focus of attention alters intracortical inhibition within the primary motor cortex. Acta Physiol (Oxf) 2017;220:289-299.
34. Benjaminse A, Otten E. ACL injury prevention, more effective with a different way of motor learning? Knee Surg Sports Traumatol Arthrosc 2011;19:622-7.
35. Otte FW, Davids K, Millar SK, et al. When and how to provide feedback and instructions to athletes? How sport psychology and pedagogy insights can improve coaching interventions to enhance self-regulation in training. Front Psychol 2020;11:1444.
36. Al-Abood SA, Bennett SJ, Hernandez FM, et al. Effect of verbal instructions and image size on visual search strategies in basketball free throw shooting. J Sports Sci 2002;20:271-8.
I appreciate the thoughtful considerations raised. Scientific discussion is always the best way for the opportunity to review points, exchange thoughts and evolve in knowledge. Here are some additional considerations below:
- About strength and VO2peak controlled by FFM and/or weight:
We showed these data in the article (strength/FFM; VO2peak/FFM; VO2peak/weight) in the results and table 2. There are no statistical differences comparing all populations (TW,CM and CW).
- TW with 637 ng/dL testosterone on the day of the tests:
In the long-term follow-up of a cohort of individuals with daily medication use, temporary failures in the regular use of medications are not uncommon. One of the participants had a high level of testosterone at the time of the study. However, we emphasize that we were careful to assess testosterone levels in the year before the study so that we could confirm the correlation of the values obtained at the time of the study with those in the last year. In addition, the values of haemoglobin denoted testosterone supression in the past 4 months. Although one of the TW was not blocked on test day (total testosterone =637 ng/dL), her value was 79 ng/dL six months before the study. This point did not interfere with her VO2 results (supplementary figure 2).
- Weight and height:
Studies in sports medicine generally eliminate the height as an interfering factor in the analyses.
Height is a consequent characteristic o...
I appreciate the thoughtful considerations raised. Scientific discussion is always the best way for the opportunity to review points, exchange thoughts and evolve in knowledge. Here are some additional considerations below:
- About strength and VO2peak controlled by FFM and/or weight:
We showed these data in the article (strength/FFM; VO2peak/FFM; VO2peak/weight) in the results and table 2. There are no statistical differences comparing all populations (TW,CM and CW).
- TW with 637 ng/dL testosterone on the day of the tests:
In the long-term follow-up of a cohort of individuals with daily medication use, temporary failures in the regular use of medications are not uncommon. One of the participants had a high level of testosterone at the time of the study. However, we emphasize that we were careful to assess testosterone levels in the year before the study so that we could confirm the correlation of the values obtained at the time of the study with those in the last year. In addition, the values of haemoglobin denoted testosterone supression in the past 4 months. Although one of the TW was not blocked on test day (total testosterone =637 ng/dL), her value was 79 ng/dL six months before the study. This point did not interfere with her VO2 results (supplementary figure 2).
- Weight and height:
Studies in sports medicine generally eliminate the height as an interfering factor in the analyses.
Height is a consequent characteristic of the puberty pattern that the individual had (male or female) and cis women are 13 cm shorter on average when compared to men. We have to be careful when making the correlation of height and sports performance. Men are taller and also have more muscle mass, larger heart chambers, and larger diameter of the bronchial tree. Therefore, height cannot be identified as a cause of sporting abilities, but rather as a confounding factor.
It is not weight alone that may affect sporting abilities, but muscle mass and several other factors.
Gender studies in sport often use BMI for pairing.
- Grip strength test:
The grip strength test presents results that denote an overall assessment of the individual and is largely carried out in performance studies in the most diverse populations.
Alvares et al. [1] conducted a study to compare performance-related measures such as cardiopulmonary exercise capacity and muscle strength in non-athlete transgender women (TW) undergoing long-term gender-affirming hormone therapy to non-athlete cisgender men (CM) and non-athlete cisgender women (CW). The authors report higher absolute VO2peak (L/min) and muscle strength (kg) in TW compared to CW and lower than CM. The authors conclude that their “…findings could inform policy and help in decisions about the participation of transgender women in sporting activities”.
However, the authors interpreted their findings on the basis of the absolute data they present and not the relative data that was controlled for body mass and fat-free mass (FFM), as would be appropriate for comparisons of such performance metrics (e.g., aerobic capacity and muscle strength). By focusing on the absolute data, the authors over-emphasise differences between comparison groups (e.g., TW and CW) that are clearly driven by differences in anthropometry. For example, when the data reported in Table 2 [1] are corrected for body mass and fat-free mass (FFM), differences in aerobic capacity and strength between TW and CW disappear. Yet, in the section “WHAT THIS STUDY ADDS” [1], which is the primary focus of many readers, the authors omit the results that control for body mass and FFM, instead leaving the reader with the misleading message that “[t]he mean strength and VO2peak...
Alvares et al. [1] conducted a study to compare performance-related measures such as cardiopulmonary exercise capacity and muscle strength in non-athlete transgender women (TW) undergoing long-term gender-affirming hormone therapy to non-athlete cisgender men (CM) and non-athlete cisgender women (CW). The authors report higher absolute VO2peak (L/min) and muscle strength (kg) in TW compared to CW and lower than CM. The authors conclude that their “…findings could inform policy and help in decisions about the participation of transgender women in sporting activities”.
However, the authors interpreted their findings on the basis of the absolute data they present and not the relative data that was controlled for body mass and fat-free mass (FFM), as would be appropriate for comparisons of such performance metrics (e.g., aerobic capacity and muscle strength). By focusing on the absolute data, the authors over-emphasise differences between comparison groups (e.g., TW and CW) that are clearly driven by differences in anthropometry. For example, when the data reported in Table 2 [1] are corrected for body mass and fat-free mass (FFM), differences in aerobic capacity and strength between TW and CW disappear. Yet, in the section “WHAT THIS STUDY ADDS” [1], which is the primary focus of many readers, the authors omit the results that control for body mass and FFM, instead leaving the reader with the misleading message that “[t]he mean strength and VO2peak in non-athlete TW … were higher than those in non-athlete CW.”
Relatedly, we question the authors’ reliance on expressing lung volume relative to body mass and FFM, when expressing relative to height would be more informative. The important relationship between height and indices of cardiovascular function/capacity is widely recognised [2]. However, Alvares et al. only report the heights of participants in their supplementary data [1] – which will mostly be overlooked by many reading the paper. Our own analysis of the supplementary data shows that height differences between TW and CW could fully account for the absolute differences in lung capacity. Again, the key finding here would be an absence of difference in relative aerobic capacity of cisgender versus transgender women.
In addition to the biased message, there are also many other basic errors in this manuscript that questions its value as published to inform policy. In the interest of brevity our main concerns are listed below as follow:
1. We question why one of the TW participants had a very high level of testosterone on the day of testing (TT=637 ng/dL). The authors justified the inclusion of this subject’s testing results on the basis of her having had a lower testosterone level six months prior. However, this is a cross-sectional study, meaning this participant should have been excluded. Without access to the raw data it is impossible to know the impact of the inclusion of this data in the comparison between groups.
2. VO2peak rather than VO2max is listed as the measure of aerobic capacity, even though VO2peak is known to underestimate the value of VO2max by 0.1-0.4 l/min [3]. It is unknown whether this represent a semantic error, or the authors have indeed measured VO2peak.
3. The authors rely on the International Physical Activity Questionnaire (IPAQ) to assess the physical activity levels of participants and match subjects in the comparison groups for meaningful data interpretation. However, the IPAQ is considered a valid instrument for measuring physical activity in large study populations, and not for such small studies needing validity at the individual level. This makes the interpretation of the comparisons between “matched” groups very difficult, if not impossible.
4. The number of participants reported in the abstract (i.e. 15 TW, 13 CM and 14 CW) does not match the number reported later in the article. The units of measurement for maximum aerobic capacity are clearly erroneous as physiologically implausible (e.g. Table 2 and VO2peak (L/min) was 2606±416.9 in TW, 2167±408.8 in CW and 3358±436.3 in CM).
5. The authors imply that gender dysphoria is a mental disorder, stating that “the criteria for gender dysphoria diagnosis were in accordance with the Diagnostic and Statistical Manual of Mental Disorder.” However, Gender Dysphoria is no longer classed as a mental health disorder [4].
In conclusion, we suggest that, as presented, the paper by Alvares et al. [1] cannot be used to “inform policy and help in decisions about the participation of transgender women in sporting activities”. Instead, the scientific community including these authors should be encouraged to conduct and publish high quality studies involving trained transgender individuals (and athletes where possible) and involving sport-specific measures to inform policy and guidelines [5].
References
1. Alvares LAM, Santos MR, Souza FR, Santos LM, Mendonça BB, Costa EMF, Alves MJNN, Domenice S. Cardiopulmonary capacity and muscle strength in transgender women on long-term gender-affirming hormone therapy: a cross-sectional study. Br J Sports Med. 2022 Nov;56(22):1292-1298.
2. HEPPER NG, FOWLER WS, HELMHOLZ HF Jr. Relationship of height to lung volume in healthy men. Dis Chest. 1960 Mar;37:314-20. PMID: 14401182.
3. Smirmaul BP, Bertucci DR, Teixeira IP. Is the VO2max that we measure really maximal? Front Physiol. 2013 Aug 5;4:203.
4. Rodríguez MF, Granda MM, González V. Gender incongruence is no longer a mental disorder. Journal of Mental Health & Clinical Psychology. 2018;2(5).
5. Martowicz M, Pape M, Budgett R, Mascagni K, Engebretsen L, Dienstbach-Wech L, Pitsiladis Y, Pigozzi F, Erdener U. Position Statement: IOC Framework on Fairness, Inclusion and Non-Discrimination on the Basis of Gender Identity and Sex Variations. British Journal of Sports Medicine. In review.
The topic of transgender inclusion in women’s sports is politically fraught. Sport’s governing bodies are grappling with the competing priorities of inclusivity and fairness due to any perceived competitive advantage above and beyond the large and broad continuum of biological variables found within cisgender women (e.g. height, bone mass, bone length, fiber cross-sectional diameter, etc.) associated with testosterone exposure during puberty. This active area of research is rapidly evolving due to the multitude of new studies published over the previous 5 years. In fact, there have been over a dozen primary prospective and case-control research studies published on this topic since 2018 resulting in the lowering of the maximum allowable testosterone level in transgender elite athletes (i.e., from 5.0 to 2.5nmol/L) by several sports’ governing bodies.
The preponderance of evidence suggests that hematological differences in hematocrit, red cell number, and hemoglobin are largely normalized within 120 days of testosterone suppression, which is biologically plausible as this corresponds with the average lifespan of a red cell (~ 120 days). Since oxygen delivery to peripheral tissues is performance limiting in aerobic sports, any competitive advantage is likely largely diminished within a year of testosterone suppression. Studies evaluating changes in strength, muscle mass, and body composition are more equivocal and most likely occur over a longer time span (12-36 mon...
The topic of transgender inclusion in women’s sports is politically fraught. Sport’s governing bodies are grappling with the competing priorities of inclusivity and fairness due to any perceived competitive advantage above and beyond the large and broad continuum of biological variables found within cisgender women (e.g. height, bone mass, bone length, fiber cross-sectional diameter, etc.) associated with testosterone exposure during puberty. This active area of research is rapidly evolving due to the multitude of new studies published over the previous 5 years. In fact, there have been over a dozen primary prospective and case-control research studies published on this topic since 2018 resulting in the lowering of the maximum allowable testosterone level in transgender elite athletes (i.e., from 5.0 to 2.5nmol/L) by several sports’ governing bodies.
The preponderance of evidence suggests that hematological differences in hematocrit, red cell number, and hemoglobin are largely normalized within 120 days of testosterone suppression, which is biologically plausible as this corresponds with the average lifespan of a red cell (~ 120 days). Since oxygen delivery to peripheral tissues is performance limiting in aerobic sports, any competitive advantage is likely largely diminished within a year of testosterone suppression. Studies evaluating changes in strength, muscle mass, and body composition are more equivocal and most likely occur over a longer time span (12-36 months).
Few studies have evaluated cardiopulmonary differences in transgender women relative to cisgender women or men. The recent publication by Alvares et. al. evaluated cardiopulmonary capacity and grip strength in a small cohort of non-athlete cisgender and transgender women (CW and TW) and cisgender men (CM) in San Paulo, Brazil. 15 transgender women were recruited from a clinic that specializes in the treatment transgender patients. The average age of the TW was 34.2 +/- 5.2 years with an average duration of hormonal treatment of 14.4+/-3.5 years (median age of treatment initiation was 17 years old). Although the TW subjects were on hormonal treatment for over a decade, 11 of the 15 subjects were dependent on chemical testosterone suppression (i.e., non-gonadectomized). The median testosterone level over the previous 12 months for the TW subjects was 3.5nmol/L with 4 of the subjects above 7nmol/L, which is within the range observed CM group. As noted above, several sports’ governing bodies require testosterone suppression below 2.5nmol/L throughout the entire year. Prospective testosterone data for each subject was not provided so it is unclear how many TW subjects meet these criteria, however median levels presented in supplemental figure 1 suggest that at least 8 out of 15 of the subjects do not meet this criterion. Despite the suboptimal hormonal control, hemoglobin levels of the TW were not different than CW and both groups were significantly lower than the CM group. Although the groups were matched by age and activity, they were not weight matched. The average body weights were 60.8kg, 78.1kg, and 81.3kg for the CW, TW, CM groups respectively (CW vs TW and CW vs CM were significantly different; P < 0.001).
The authors performed cardiopulmonary exercise testing on a treadmill using a ramp protocol to exhaustion. They measured oxygen consumption at rest (prior to running), at anaerobic threshold (AT), at respiratory compensation point (RCP), and peak consumption. Values were provided on an absolute basis (mL/min) at rest, AT, RCP. VO2 peak was presented on absolute and relative basis (relative to total body weight and fat free mass [FFM]; L/min/kg). The absolute oxygen consumption at rest, at RCP, and peak consumption were higher in the TW group relative to the CW group. This is not surprising since the average body weight of the TW was 22% heavier than the CW group.
Conceptually speaking, someone that is heavier (i.e. has a higher fat free mass) is more metabolically active and will consume more oxygen per time period. The authors do present peak oxygen consumption normalized to total body weight and fat free mass. When doing so, differences in the peak oxygen consumption disappear. In fact, when normalized to FFM, VO2 peak was 11% less in the TW group relative to the CW group although the differences were not statistically different. When corrected to body weight, no differences in oxygen consumption were observed between the CW and TW groups (Rest - 4.2 vs 4.0L/kg/min; AT - 21.6 vs. 21.5L/kg/min; RCP - 29.6 vs. 31.5 L/kg/min; Peak - 33.4 vs 35.7 L/kg/min). This is an important point because it suggests that there are no differences in cardiopulmonary capacity in TW compared to CW when normalized to body weight. Although these subjects reported high activity levels, the peak oxygen consumption (VO2 peak) for the CW, TW, and CM groups was roughly half the VO2 peak observed in most elite athletes (>60 L/kg/min). These results should not be extrapolated to elite athletes.
The authors also assessed grip strength to evaluate whether there were any strength differences between TW and CW and CM. There was a statistically significant increase in grip strength between TW and CW, however this finding was no longer significant after normalizing to body weight. Nevertheless, it is unclear the relevance of grip strength to predicting any performance advantage to most elite or professional sports.
Owing to the scientific rigor and careful interpretation of results from previous case-control and prospective research studies, the results from these studies have advanced our understanding of the physiological changes associated with testosterone exposure during puberty and subsequent withdrawal on human exercise performance. The amalgamation of the available data has allowed sports’ governing bodies the ability to make highly informed policy decisions on managing a balance between inclusivity and fairness in female transgender athletes. It is incumbent that all new studies in this area of research are of high scientific rigor and the associated conclusions are appropriate for the data that are presented because the results and the language used have imminent ramifications for the inclusion of transgender athletes to compete in sport. The conclusions presented by Alvares et al are incomplete and not fully supported by the data. Further and perhaps more importantly, the conclusions by the authors suggesting that TW have higher cardiopulmonary function (unadjusted for body weight) is harmful to the sporting community at large because it submits false evidence of a competitive advantage. Although the study was conducted in non-athletes, the authors suggest the results from their study may inform inclusion policies for transgender athletes. In fact, the data from Alvares et al suggest that TW do not have improved cardiopulmonary function relative to CW or TW when normalized to body weight. Thus, the study does not provide evidence of a competitive advantage in sports in this small cohort of non-athletes. As such, it does not support further restrictions of transgender athletes from sport.
I congratulate you for researching the importance of appropriate soccer
ball size. Your article on distal radial fractures was cited in The New
York Times shortly after being published, shedding light on a potentially
preventible injury in soccer. It seems possible that if children just
played with junior-sized balls, fewer would get hurt by distal radial
fractures.
I would like to add some...
I congratulate you for researching the importance of appropriate soccer
ball size. Your article on distal radial fractures was cited in The New
York Times shortly after being published, shedding light on a potentially
preventible injury in soccer. It seems possible that if children just
played with junior-sized balls, fewer would get hurt by distal radial
fractures.
I would like to add some comment for further research in this area. In
order to truly establish ball size as a causative factor, one must know
the baseline, overall usage of adult vs. junior-size balls. This can be
done by surveying the field play to get a rough estimate of the division
into adult and junior usage. I think, for this study, it was assumed that
usage was about even: fifty percent of the study population played with a
junior-sized ball and fifty with adult. However, it is possible to
imagine that more players used the bigger (adult) ball, since the
"recommendations are not in universal use." If this occurred, the
chances were much higher for observing in the clinic injuries resulting
from adult-size balls. It is comparable to finding in a study that "90%
of accidents happen within 10 kilometers of home." This is bound to
happen by chance alone. I am more convinced by results from a test of
significance when this qualification measure is taken into account.
In their recent article 'Intensive training in elite young female
athletes,' Baxter-Jones and Maffulli reviewed 18 manuscripts and concluded
'training does not appear to affect growth and maturation .'[1] We have
two concerns about this conclusion. First, we agree that analyses of cross
-sectional and cohort data in this population are confounded by sampling
bias; gymnasts who are successful at an elite leve...
In their recent article 'Intensive training in elite young female
athletes,' Baxter-Jones and Maffulli reviewed 18 manuscripts and concluded
'training does not appear to affect growth and maturation .'[1] We have
two concerns about this conclusion. First, we agree that analyses of cross
-sectional and cohort data in this population are confounded by sampling
bias; gymnasts who are successful at an elite level are likely to be self-
selected by their small stature and delayed maturation. Frequently,
however, data from cross-sectional and cohort studies are averaged. This
'group' approach provides little information about individual growth
patterns. Thus, in Baxter-Jones and Maffuli's review, and the literature
at large, an important basic question has been overlooked; that is, is
there any evidence that growth and/or maturation are adversely affected in
some athletes and if so, what is the frequency of this condition?
Second, in contrast to their findings, our analysis of over 35
clinical reports, cross-sectional and historical and prospective cohort
studies indicates that elite level gymnasts may be at risk for adverse
effects on growth [2]. We reported that the increased magnitude of the
delay in skeletal maturation with training in adolescent female gymnasts,
coupled with the occurrence of catch-up growth during periods of reduced
training or retirement, provides evidence that growth and maturation may
be affected in some instances [2,3]. Furthermore, in contrast to the
interpretation Baxter-Jones and Maffulli made of our data, we did report
an association between reduced growth and years of gymnastic training, and
that the deficits were greater at the axial than appendicular skeleton
[3].
We are in agreement with Baxter-Jones and Maffulli that a cause-
effect relationship between gymnastics training and inadequate growth of
females has not been demonstrated; there have been no randomized
controlled trials. However, this does not mean there is 'no evidence for
inadequate growth among female gymnasts.' If clinicians are coerced by
group means and ignore variability about the mean, then gymnasts who are
at increased risk of reduced growth may be overlooked. We recommend that
the growth of all young elite female gymnasts should be monitored
regularly. Any gymnast who falls behind in growth i.e. across two major
percentiles of the growth chart, should undergo a complete evaluation for
underlying pathology, even when height is not below the fifth percentile.
This may be normal short stature, but the clinical criterion warrants
assessment.
References
(1) Baxter-Jones ADG, Maffulli N, Intensive training in elite young
female athletes Br J Sports Med. 2002;36:13-15
(2) Caine D, Lewis R, O'Connor P, Howe W, Bass S. Does gymnastics training
inhibit growth of females? Clin J Sport Med 2001;11:260-70.
(3) Bass S, Bradney M, Pearce G, et al. Short stature and delayed puberty
in gymnasts: Influence of selection bias on leg length and the duration
of training on trunk length. J Pediatrics 2000;136(2):149-55.
I read with interest the report of atrial fibrillation and syncope in a body builder taking anabolic steroids and bromocriptine.[1] Drs Manoharan, Campbell and O'Brien present an interesting and perceptive report of bromocriptine misuse. Several additional points can be made regarding this case. While the authors noted the effect of the fasting state on bromocriptine kinetics,[2] in addition bromocriptine an...
I read with interest the report of atrial fibrillation and syncope in a body builder taking anabolic steroids and bromocriptine.[1] Drs Manoharan, Campbell and O'Brien present an interesting and perceptive report of bromocriptine misuse. Several additional points can be made regarding this case. While the authors noted the effect of the fasting state on bromocriptine kinetics,[2] in addition bromocriptine and methandienone share the same metabolizing enzyme, cytochrome P450 3A4.[3,4] Bromocriptine clearance has been shown to decrease with the coadministration of other drugs involving cytochrome P450 3A4 such as the macrolide antibiotics.[5]
Investigators recognised the dissociation between bromocriptine blood levels and therapeutic effects since the 1970s.[6] Over 20 years later, the clinical observations were finally explained by the work of Valente and colleagues[7] which demonstrated that hydroxylated bromocriptine metabolites are effective in reducing prolactin in the rat. Prior to this research, the specific receptor activity of bromocriptine metabolites was not characterised. In addition, possible cardiovascular effects of hydroxylated bromocriptine metabolites have not been fully investigated.
Finally, the authors note that bromocriptine had been studied in obese subjects in which weight loss and improved glucose tolerance were reported.[8] As a result of the observation of improved glycemic control after bromocriptine administration, clinical trials of bromocriptine in the treatment of Type 2 diabetes were conducted in the United States. The results of these trials were presented to the Food and Drug Administration at which time a relative risk of myocardial infarction of 2.9 after bromocriptine treatment was found.[9]
References
(1) Manoharan G, Campbell NPS, O'Brien C.J. Syncopal episodes in a young amateur body builder. Br J Sports Med 2002;36:67-8.
(2) Drewe J, Mazer N, Abisch E, et al. Differential effect of food on kinetics of bromocriptine in a modified release capsule and a conventional formulation. Eur J Clin Pharmacol 1988;35:535-41.
(3) Wynalda M, Wienkers L. Assessment of potential interactions between dopamine receptor agonists and various human cytochrome P450 enzymes using a simple in vitro inhibition screen. Drug Metab Dispos 1997;25:1211-4.
(4) Rendic S, Nolteernsting E, Schanzer W. Metabolism of anabolic steroids by recombinant human cytochrome P450 enzymes. Gas chromatographic-mass spectrometric determination of metabolites. J Chromatogr B Biomed Sci Appl 1999;735(1):73-83.
(5) Periti P, Mazzei T, Mini E, Novelli A. Pharmacokinetic drug interactions of macrolides. Clin Pharmacokinet 1992;23:106-31.
(6) Jenner P, Marsden CD, Reavill C. Evidence for metabolite involvement in bromocriptine-induced circling behavior. Br J Pharmacol 1979;66(1):103P-4P.
(7) Valente D, Delaforge M, Urien S, et al. Metabolite involvement in bromocriptine-induced prolactin inhibition in rats. J Pharmacol Exp Ther 1997;282:1418-24.
(8) Cincotta AH, Meier AH. Bromocriptine (Ergoset) reduces body weight and improves glucose tolerance in obese subjects. Diabetes Care 1996;19:667-70.
(9) Food and Drug Administration. Endocrinologic and Metabolic Drugs Advisory Committee. 70th Meeting. Bethesda,MD: Food and Drug Administration, May 14, 1998:Meeting Transcript, page 135.
With regards to the excellence of the Australians in the last
Olympics, a small reposte is required. We need to examine Darwinism to
fully understand this concept. As you pointed out the Aussies did
exceptionally well in the water but have yet to fully evolve and are still
swimming. The Brits on the otherhand are further along the evolutionary
scale and have realised that to get from one island to...
With regards to the excellence of the Australians in the last
Olympics, a small reposte is required. We need to examine Darwinism to
fully understand this concept. As you pointed out the Aussies did
exceptionally well in the water but have yet to fully evolve and are still
swimming. The Brits on the otherhand are further along the evolutionary
scale and have realised that to get from one island to another you don't
need to swim, you can sail. And as for rugby (Union the proper code) I do
believe the English beat them recently. The other code attempted a
"world" cup recently but each side was made up of Australians and was
starting to resemble the US's version of a world series.
I read with great interest the article by Waddington, Roderick and
Naik regarding the appointment and qualifications of club doctors and
physiotherapists in English professional football.
Further to the messages put over in the text I feel that from a
physiotherapy side, just being chartered is not enough. In my experience
many professional clubs are employing chartered physiotherapists, s...
I read with great interest the article by Waddington, Roderick and
Naik regarding the appointment and qualifications of club doctors and
physiotherapists in English professional football.
Further to the messages put over in the text I feel that from a
physiotherapy side, just being chartered is not enough. In my experience
many professional clubs are employing chartered physiotherapists, straight
out of University to look after their academies and so comply with the
first regulations of employing Chartered physiotherapists.
These physiotherapists, have little (if no) experience of managing
the injuries of professional sport, and are been given the responsibility
of looking after the medical needs of junior footballers. There is a move
afoot within the Association of Chartered Physiotherapists in Sports
Medicine to ally with the National Athletic Trainers Association in
America with the possibility of producing Sports Rehabilitation and
athletic trainers within this country as recognised therapists to work
within sports.
I would urge all involved in the employment of physiotherapists
within sport to look for suitable candidates who have a good understanding
of the management of sports-related injury.
This will mean that the pay scales within professional football, on
the medical side, will need adjusting accordingly.
At the time when clubs are worrying about the abolition of transfer
fees - stating that fees are linked to the "skill level" of the player. I
feel the same system of financial compensation be applied within the
medical set-up, thus raising the standard of medical back up within
soccer.
Ian Horsley MCSP SRP
Lecturer In Sports Rehabilitation
University of Salford, Manchester, UK
There is absolutely no doubt that physical activity is a beautiful phenomenon. In the above study, the study is fair to the extent that those subjects who regularly exercised had lesser hospitalisations. Here both reason and effect exist, but can a direct causal relationship be established between the two?
Can it be inferred beyond doubt that "the vaccine prevented complications of Covid-19 because exercise strengthened the immune response? The possibility of such a remarkable effect in the short term is pretty unlikely. And all the more, such findings can't be generalised to a larger population.
Authors seem to be ignoring a hidden confounder affecting the validity of the study, and this confounder is 'frailty'. Simply those doing less exercise were unable to do so because they were frail. And obviously, frailty can be present independent of comorbidities like DM, heart failure or obesity, which were evenly matched between the high and low-exercise groups.
So, the correct conclusions will likely differ if this confounder is considered. one may not forget that 'Correlation, even if present in a statistically significant portion, may not amount to causation.
The study might prompt some frail people or even morbidly obese people to engage in heavy exercise soon after the vaccination despite muscle aches and fever (common side effects of the Covid-19 vaccines). And these might have disastrous consequences. So the wo...
Show MoreAnne Benjaminse,1,2 Alli Gokeler3, 4, 5
1 University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, Netherlands
2 School of Sport Studies, Hanze University Groningen, Groningen, the Netherlands
3 Exercise Science and Neuroscience, Department Exercise & Health, Faculty of Science, Paderborn University, Paderborn, Germany
4 Amsterdam Collaboration for Health and Safety in Sports, Department of Public and Occupational Health, Amsterdam Movement Sciences, VU University Medical Center, Amsterdam, The Netherlands.
5 OCON Center of Orthopaedic Surgery and Sports Medicine, Hengelo, The Netherlands
Dear Editor,
Show MoreWe read the recent manuscript by Kal et al.1 ‘Explicit motor learning interventions are still relevant for ACL injury rehabilitation: do not put all your eggs in the implicit basket‘ with great interest. The authors did a commendable job summarizing the current literature and we highly respect them for being critical, to foster academic discussions to move science forward. We do however have some concerns regarding the methodology and interpretations made by the authors.
Confusing definition: description vs. execution First, the authors write: "Elite athletes have shown to successfully use explicit interventions to de-automate, and subsequently improve, problematic movements.“.2 The paper by Toner et al. is largely based on assumptions, case studies and philosop...
I appreciate the thoughtful considerations raised. Scientific discussion is always the best way for the opportunity to review points, exchange thoughts and evolve in knowledge. Here are some additional considerations below:
- About strength and VO2peak controlled by FFM and/or weight:
We showed these data in the article (strength/FFM; VO2peak/FFM; VO2peak/weight) in the results and table 2. There are no statistical differences comparing all populations (TW,CM and CW).
- TW with 637 ng/dL testosterone on the day of the tests:
In the long-term follow-up of a cohort of individuals with daily medication use, temporary failures in the regular use of medications are not uncommon. One of the participants had a high level of testosterone at the time of the study. However, we emphasize that we were careful to assess testosterone levels in the year before the study so that we could confirm the correlation of the values obtained at the time of the study with those in the last year. In addition, the values of haemoglobin denoted testosterone supression in the past 4 months. Although one of the TW was not blocked on test day (total testosterone =637 ng/dL), her value was 79 ng/dL six months before the study. This point did not interfere with her VO2 results (supplementary figure 2).
- Weight and height:
Show MoreStudies in sports medicine generally eliminate the height as an interfering factor in the analyses.
Height is a consequent characteristic o...
Dear Editor:
Alvares et al. [1] conducted a study to compare performance-related measures such as cardiopulmonary exercise capacity and muscle strength in non-athlete transgender women (TW) undergoing long-term gender-affirming hormone therapy to non-athlete cisgender men (CM) and non-athlete cisgender women (CW). The authors report higher absolute VO2peak (L/min) and muscle strength (kg) in TW compared to CW and lower than CM. The authors conclude that their “…findings could inform policy and help in decisions about the participation of transgender women in sporting activities”.
However, the authors interpreted their findings on the basis of the absolute data they present and not the relative data that was controlled for body mass and fat-free mass (FFM), as would be appropriate for comparisons of such performance metrics (e.g., aerobic capacity and muscle strength). By focusing on the absolute data, the authors over-emphasise differences between comparison groups (e.g., TW and CW) that are clearly driven by differences in anthropometry. For example, when the data reported in Table 2 [1] are corrected for body mass and fat-free mass (FFM), differences in aerobic capacity and strength between TW and CW disappear. Yet, in the section “WHAT THIS STUDY ADDS” [1], which is the primary focus of many readers, the authors omit the results that control for body mass and FFM, instead leaving the reader with the misleading message that “[t]he mean strength and VO2peak...
Show MoreThe topic of transgender inclusion in women’s sports is politically fraught. Sport’s governing bodies are grappling with the competing priorities of inclusivity and fairness due to any perceived competitive advantage above and beyond the large and broad continuum of biological variables found within cisgender women (e.g. height, bone mass, bone length, fiber cross-sectional diameter, etc.) associated with testosterone exposure during puberty. This active area of research is rapidly evolving due to the multitude of new studies published over the previous 5 years. In fact, there have been over a dozen primary prospective and case-control research studies published on this topic since 2018 resulting in the lowering of the maximum allowable testosterone level in transgender elite athletes (i.e., from 5.0 to 2.5nmol/L) by several sports’ governing bodies.
The preponderance of evidence suggests that hematological differences in hematocrit, red cell number, and hemoglobin are largely normalized within 120 days of testosterone suppression, which is biologically plausible as this corresponds with the average lifespan of a red cell (~ 120 days). Since oxygen delivery to peripheral tissues is performance limiting in aerobic sports, any competitive advantage is likely largely diminished within a year of testosterone suppression. Studies evaluating changes in strength, muscle mass, and body composition are more equivocal and most likely occur over a longer time span (12-36 mon...
Show MoreDear Editor
I congratulate you for researching the importance of appropriate soccer ball size. Your article on distal radial fractures was cited in The New York Times shortly after being published, shedding light on a potentially preventible injury in soccer. It seems possible that if children just played with junior-sized balls, fewer would get hurt by distal radial fractures. I would like to add some...
In their recent article 'Intensive training in elite young female athletes,' Baxter-Jones and Maffulli reviewed 18 manuscripts and concluded 'training does not appear to affect growth and maturation .'[1] We have two concerns about this conclusion. First, we agree that analyses of cross -sectional and cohort data in this population are confounded by sampling bias; gymnasts who are successful at an elite leve...
Dear Editor
I read with interest the report of atrial fibrillation and syncope in a body builder taking anabolic steroids and bromocriptine.[1] Drs Manoharan, Campbell and O'Brien present an interesting and perceptive report of bromocriptine misuse. Several additional points can be made regarding this case. While the authors noted the effect of the fasting state on bromocriptine kinetics,[2] in addition bromocriptine an...
Dear Editor
With regards to the excellence of the Australians in the last Olympics, a small reposte is required. We need to examine Darwinism to fully understand this concept. As you pointed out the Aussies did exceptionally well in the water but have yet to fully evolve and are still swimming. The Brits on the otherhand are further along the evolutionary scale and have realised that to get from one island to...
Dear Editor
I read with great interest the article by Waddington, Roderick and Naik regarding the appointment and qualifications of club doctors and physiotherapists in English professional football.
Further to the messages put over in the text I feel that from a physiotherapy side, just being chartered is not enough. In my experience many professional clubs are employing chartered physiotherapists, s...
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