Some decades ago, Tom Beauchamp and James Childress proposed four principles for biomedical ethics (i.e., respect for autonomy, non-maleficence, beneficence, and justice). They postulated that such an approach, called principlism, could be applied universally. 1
The relationship between regular physical activity and the prevention of some diseases has been disseminated widely in scientific literature. 2 Pugh et al. 3 highlighted the importance of broadening the debate on this relationship and not relying solely on the principle of beneficence. It would also be necessary for the authors to acknowledge practically the principle of non-maleficence. Within this perspective, Pugh et al. 3 commented on the risk of damage, possibly even death, from vigorous physical exercise for the practitioners (whom they called patients).
It is worth noting that the principles of non-maleficence and beneficence have played a central role in the history of biomedical ethics. However, respect for autonomy and justice seem to be often neglected. 1 Even though we may agree on some points with Pugh et al. 3, it is imperative to bring other bioethical principles to the debate.
Thus, we would like to contribute, although briefly, to the debate on the topic addressed by Pugh et al. 3 and suggest that the focus on non-maleficence should be broadened. In addition, we highlight the indispensable focus on the principle of justice and autonomy.
Regarding the expansion of the non-maleficence principle, it has been shown that occupational physical activity can be harmful to one’s health, extending the physical activity paradox beyond the harmful effects of intensity. 4 This finding contradicts the idea that physical activity in its various dimensions is beneficial.
Another point that deserves wide attention concerns inequalities and how they impact various aspects of individuals’ relationships with physical exercise. Various studies have indicated that the vulnerability of certain social groups—such as black people, people of low socioeconomic status, and women—interferes with the performance of leisure-time physical activities or even other behaviours considered as healthy 5–6. We view this as an affront to the principle of justice. Moreover, some researchers have disregarded such inequalities and reinforced blaming the individual for his or her ‘failure’ to engage in behaviour considered appropriate, even arguing that it leads to enormous economic costs to society. 7 This position clearly aligns with neoliberal precepts since it places the responsibility for taking care of oneself on the individual, thus removing it from the State. Why, in general, are women less involved with leisure-time physical activities than men? Why is the same true for black people? Why is physical inactivity lower among black women? How do violence, mobility, and urban planning impact physical activity? Are more impoverished people equally likely to have access to leisure-time physical activity? The possibility of exercising does not seem equal for everyone.
Although we recognise that the focus of Pugh et al. 3 was correct medically, we consider that inequities interfere decisively in the possibility that any isolated measure effectively produces some benefit and/or avoids some harm. The principles of beneficence and non-maleficence may not be guaranteed if effective measures to combat inequities are not adopted. Regarding the context of peripheral countries, it is essential to consider adequate bioethical theories, rather than principlism. 8
In particular, socially excluded people—because of their unequal position in society—may sometimes be unable to make autonomous decisions. The capacity to make decisions is in itself incomplete, relative, non-global, and determined by a series of changing contextual aspects.
We also consider it necessary to question the supposed universality of bioethical principles since they are often presented within a colonialist perspective. This posture is reflected in individuals’ concepts of autonomy, which we believe should be decolonised. Decolonisation stimulates the debate about the knowledge and experiences of the community to reveal their richness. This process is in line with a vision of social justice: achieving health equity considering individual and collective empowerment. Therefore, taking advantage of the knowledge and perspectives of social groups to contribute to the development of specific interventions seems essential for yielding effective results.
Finally, we highlight the insistence on considering the relationship between physical exercise and health as a problem that is only biomedical. The resulting discourses reinforce the idea of the medicalisation of exercise. Thus, the practitioner becomes a patient and the pleasure for the practice is always neglected.

References
1. Beauchamp TL, Childress JF. Principles of biomedical ethics. 8 ed. New York: Oxford University Press, 2019.
2. Booth FW, Roberts CK, Laye MJ. Lack of Exercise Is a Major Cause of Chronic Diseases. Compr Physiol 2012; 2:1143-1211.
3. Pugh J, Pugh C, Savulescu, J. Exercise prescription and the doctor’s duty of non-maleficence. Br J Sports Med 2017; 51:1555-1556.
4. Holtermann A, Schnohr P, Nordestgaard BG, Jacob Louis Marott JL. The physical activity paradox in cardiovascular disease and all-cause mortality: the contemporary Copenhagen General Population Study with 104 046 adults. Eur Heart J 2021; 42:1499-1511.
5. Brodersen NH, Steptoe A, Boniface DR, Wardle J. Trends in physical activity and sedentary behaviour in adolescence: ethnic and socioeconomic differences. Br J Sports Med 2007; 41:140-144.
6. Abichahine H, Veenstra G. Inter-categorical intersectionality and leisure-based physical activity in Canada. Health Promot Int 2017; 32:691-701.
7. Allender S, Foster C, Scarborough P, Rayner M. The burden of physical activity-related ill health in the UK. J Epidemiol Community Health 2007; 61:344-348.
8. Garrafa V, Porto D. Intervention bioethics: a proposal for peripheral countries in a context of power and Injustice. Bioethics 2003; 17: 399-416.

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
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