Recent eLetters

Age cheats are a common problem in Youth Tournaments in Sub Saharan Africa with poor record keeping practices in rural areas. The MRI will help greatly in our quest to stamp out age cheats but more research needs to be done to determine the sensitivity of the MRI in determining ages of African Athletes as current evidence shows that there may be some false positives going by the current grading system. Some scientists argue that the environment and nutritional differences across Africa might delay fusion of the wrist. As such more research needs to be done to develop a more accurate grading system.

Dear Editor

We have read with interest the recently reported accelerometer study of physical activity in community-living seniors in Oxfordshire (1). Subjects were observed for 7 days, apparently in the winter or the spring, although the only clue to the important question of season is that invitations were sent out over a 20-week period, beginning in September of 2006. In discussing their data, the authors claim (p. 446) �gThis is the first moderately sized population-based study of older people published to date with objective PA measures and a broad range of health, psychological and anthropometric variables.�h

In fact, a much more extensive community study of seniors aged 65-99 years has been conducted previously, in the Japanese community of Nakanojo. Many of the key findings from the Nakanojo Study have been published, and are summarized in a recent review (2). The Japanese subjects were monitored 24 hours per day for an entire year, thus avoiding problems from seasonal variations in physical activity (3-6). Perhaps in part because seasonal effects are quite large in this age group, the average step counts over the whole year were somewhat higher than the 6443 steps/day reported by Harris et al. (1), particularly in the male subjects. It would be interesting to have for comparison British data that also covers an entire year. Like Harris et al. (1), we found associations of step counts with age, sex, body build, physical, metabolic and psychological health among other environmental, geographic and psycho- social variables, and our data support the view that in Asia, as in Europe, many seniors are currently taking substantially less than the recommended daily dose of physical activity.

Yukitoshi Aoyagi

REFERENCES

1. Harris TJ, Owen CG, Victor CR, et al. What factors are associated with physical activity in older people, assessed objectively by accelerometry? Br J Sports Med 2009; 43: 442-450.

2. Aoyagi Y, Shephard RJ. Steps per day. The road to senior health? Sports Med 2009; 39: 423-438.

3. Togo F, Watanabe E, Park H, et al. Meteorology and the physical activity of the elderly: the Nakanojo Study. Int J Biometeorol 2005; 50: 83-89.

4. Togo F, Watanabe E, Park H, et al. How many days of pedometer use predict the annual activity of the elderly reliably? Med Sci Sports Exerc 2008; 40: 1058-1064.

5. Yasunaga A, Togo F, Watanabe E, et al. Sex, age, season, and habitual physical activity of older Japanese: the Nakanojo Study. J Aging Phys Act 2008; 16: 3-13.

6. Shephard RJ, Aoyagi Y. Seasonal variations in physical activity and implications for human health. Eur J Appl Physiol 2009; in press. doi: 10.1007/s00421-009-1127-1.

Dear Editor

We appreciate the thoughtful review of our manuscript by Hancock, Ste -Marie and Young.(1) In this brief response, we reconsider the issues raised in their review and continue the discussion of relative age effects in National Hockey League (NHL) draftees.

REGARDING THE APPROPRIATE USE OF CUTOFF DATES.

Hancock et al. proposed that the more appropriate method for examining relative age effects in NHL draft players was to use the age cutoff criterion established by the NHL (September 16th). Our original analyses(2) utilized the age cutoff from the Hockey Canada and Hockey USA governing bodies (January 1st). Although the cutoff used by Hancock et al. seems reasonable, we submit that our original analyses were more appropriate because the proposed mechanisms of relative age effects are known to originate early in an athlete’s development.(3)

In sport, relative age attainment differentials are proposed to result from physical maturation differences among individuals during growth and development. (4) Specifically, those born shortly after the cut -off date established by sport governing bodies typically display more mature physical characteristics compared to those born later in the year. (5) Greater height, strength, speed and power not only relate to maturity, but also provide physical attributes that underpin performance in many sports. As a result, earlier-born, more mature individuals are more likely to dominate youth sport, be identified as ‘outstanding’ and be selected by scouts and coaches for representative sport competition. (4)

More competitive levels of sport participation are associated with dramatic changes in the practice environment. Here, selected athletes access practice more frequently and dedicate an increasingly significant proportion of weekly time to training with more highly qualified and specialized coaches to facilitate continued development. Thus selection and access to quality practice propagate relative age effects well into the senior years, explaining why discrepancies in birth date tendencies have been reported repeatedly across professional sports.(4) Interestingly, a recent meta-analysis by our research team found that relative age effects were strongest in adolescence and diminished in adulthood. (4)

In summary, the cutoff dates associated with early development drive relative age effects, not the cutoff date used for the NHL draft. Altering the cutoff date as we saw from Hancock et al. should have little influence on the overall effect. Their re-analysis indicates the largest representation was in birth quarter two followed by birth quarter three, which, as they showed, corresponds better to a relative age effect originating from the Hockey Canada and Hockey USA cutoff date of January 1st than September 1st.

REGARDING THE USE OF ALL DRAFT ROUNDS

Hancock et al criticized our choice to use all seven rounds of the draft for our relative age analyses on the basis that later rounds are made up of lower quality players. This seems like splitting hairs to us, as this rationale could also be used to justify using only round one instead of rounds two to four or the first 10 players of round one versus the remaining 20 players in round one. Moreover, our paper was written to demonstrate that the relative age effect explained some of the results for the NHL draft, not the performance of the draftees after they had entered the NHL. We defend our original choice on the basis that any selection in the NHL represents a reasonable level of expertise to examine the relative age effect in this population. Furthermore, and perhaps more interesting, an additional analysis of our data comparing relative age distributions for rounds one to four with rounds five to nine (up to 2005 the NHL draft had nine rounds), noted a slightly stronger relative age effect in later rounds than earlier rounds (Cramér’s V = 0.08 for rounds 1-4 and 0.13 for rounds 5-9).

REGARDING DRAFT VERSUS OVERALL SELECTION FOR SPEARMAN CORRELATION

The rationale for using an athlete’s overall selection in the draft versus round number is reasonable, as it adds additional depth to the selection variable. However, coaches, athletes and spectators rarely talk about athletes in terms of what their overall selection was – more often the overall draft round number is the characteristic of interest. Teams often have differing strategies for how they choose players in the draft (e.g., drafting to win the Stanley Cup vs. drafting for team development). As a result, players ranked highly by one team might not be considered at all by another. Removing draft round number assumes a) that each team uses the same strategy for how they choose their draft picks and b) that players can be easily rank-ordered and are equivalent from team to team. We defend our original analysis as being perhaps more relevant to the specific practices used by each team during the draft, although we appreciate the additional statistical depth that might be added by Hancock et al.’s method. The lack of consistency between our analyses and theirs is cause for concern, however, and we encourage future research in the area to elucidate these contradictory findings.

In summary, these studies continue to highlight the effects of secondary factors on long-term athlete development.

Joseph Baker

References

1. Hancock, D. J., Ste-Marie, D. M., Young, B. W. Birth date and birth place effects in National Hockey League draftees 2000-2005: Comments on Baker and Logan (2007). Br J Sports Med 2008; 42: 948-949.

2. Baker, J. Logan, A. J. Developmental contexts and sporting success: Birthdate and birthplace effects in NHL draftees 2000-2005. Br J Sports Med 2007; 41: 515-517.

3. Barnsley, R. H., Thompson, A. H. Birthdate and success in minor hockey: The key to the NHL. Can J Behav Sci 1988; 20 167-176.

4. Cobley, S., Baker, J., Wattie, N. McKenna, J. Annual age grouping and athlete development: A meta- analytical review of relative age effects in sport. Sports Med 2009; 39 235-256.

5. Sherar LB, Baxter-Jones ADG, Faulkner RA, et al. Does physical maturity and birth date predict talent in male youth ice hockey players? J Sports Sci 2007; 25: 879-86

Dear Editor,

Richards et al (2009) refer to a popular running shoe design entailing a heightened sole and pronation control. It is claimed to reduce running injuries, but in fact no evidence has been obtained to show that the design actually achieves its purpose.

May I add another thought on this topic? In a number of areas of human activity - most notably, with regard to behaviour on the roads whether as motorist or cyclist - safety features fail to be effective, because the safety advantage is eroded: the safety advantage is converted into a performance advantage (1).

Wilde, Robertson and Pless (2) refer to "risk homeostasis" to characterise this effect in its purest form. The individual "sets" a level of risk on the basis of personal factors and societal expectations: performance is then dictated by this "target" level of risk. If the perceived risk is reduced, risk homeostasis dictates that performance will increase to bring the perceived risk back to its target level. Conversely, of course, increased perception of risk will depress performance (Wilde, 1994).

It seems to me that this could be extended to this particular case. A reason that no advantage regarding injuries has been observed is that a runner may perceive the risk of injury to be reduced by employing this particular design of running shoe. As a result, the runner will increase his or her performance - thereby laying themselves open for the same level of risk that they would encounter were they not using this particular design of running shoe.

Tony H. Reinhardt-Rutland

References

(1) Reinhardt-Rutland AH, Seat-belts and behavioural adaptation: the loss of looming as a negative reinforcer. Safety Sci 2001; 39: 145-155.

(2) Wilde GJS, Robertson LS, Pless IB. Does risk homeostasis theory have implications for road safety? BMJ 2002; 324: 1149-1152.

Dear Editor

It is with great interest that I read the article by Ehrsam and collaborators in which they proposed an innovative way of increasing the exercise practice of overweight and obese individuals. [1] The system they developed attributes points to activities based on the modality and intensity of the activity, the body mass index (BMI) and the body weight of the individual. For example, an individual with a BMI between 25 and 29.9 kg/m2 who weighs over 90 kg will earn 6 points for every 10 minutes of cycling. According to the authors, overweight or obese individuals should reach optimally 200 to 300 points for health. That would suggest that this individual should cycle 50 bouts of 10 minutes per week to cumulate 300 points.

What is interesting with the system presented is that an individual can vary their activities to reach the amount of points targeted. In fact, points are given for various physical activities (basketball bowling, etc.) and activities of daily living (shopping, housekeeping, etc.). It is in this latter category that the presence of desk work can be questionned. If we take the same individual (BMI between 25 and 29.9 kg/m2), he will cumulate after 35 hours of desk work (2 points per 10 minutes) 420 points. Moreover, an individual with a BMI ≥ 40 kg/m2 will cumulate 840 points at the end of the week for the same job (desk work: 4 points per 10 minutes), which represents three times the optimum amount of points.

To counteract this situation, the authors could modify their activity point system by eliminating desk work from the list or adjusting the targeted number of points. Such changes appear important considering first that sedentary jobs are more prevalent and second that tools like the activity point system are more than needed to help overweight and obese individuals increase energy expenditure. [2]

Marie-Eve Mathieu, Ph.D. Associate Professor, Department of Kinesiology, University of Montreal Montreal (Quebec), Canada me.mathieu@umontreal.ca

References

1. Ehrsam R, Stoffel S, Koerner U, et al. Exercise Prescription for the Overweight and the Obese: How to Quantify and Yet Keep it Simple. Br J Sports Med 2009 Mar 16.

2. Bockerman P, Johansson E, Jousilahti P et al. The physical strenuousness of work is slightly associated with an upward trend in the BMI. Soc Sci Med 2008;66:1346-55.