Dear Editors,

Knechtle and Kohler have considered the factors relating to overall performance in triple ironman triathlon. There are however several other considerations which must be made when looking at total race time.

The mental preparation needed for ultra-endurance events may have a significant impact on total race time. This can limit training time and total race time, especially if an individual misjudges their pacing early in the event.

Some consideration needs to be taken of pre-race injuries. Endurance athletes commonly have a number of injuries which limit different aspects of their preparation and race. With a sample size of only 17, these two factors are likely to prevent any true association between anthropomorphic factors and total race time.

The study of triple ironman distance events is unusual as there are few events of this type globally. Comparisons to marathon running, ironman triathlon and cycling are perhaps misguided as these are all sports with large numbers of competitors and a circuit of races for professional athletes.

Subjects in this study trained between only 6 hours each week and up to 55 hours. Skin fold thickness was high indicating a high body fat percentage. Average weight was 85Kg, considerably higher than most professional ironman triathletes. Competitors clearly varied considerably in their preparation. They range between casual competitors and professional athletes. This makes study of the factors needed for low total race time difficult.

The use of performance in individual sections of the race may not be a valid measurement to make alone. Whilst there is a trend towards time in the running section being the best predictor of total race time, this is in fact also a function of both cycling time and swimming time. The energy expended in other sections of the event will take a toll on the later part even with the best athletes. As the last section of the race the run is most likely to show a trend.

Despite the thorough analysis made of the results, currently there is insufficient participation in this type of event for this type of study. As the popularity of ultra-endurance sport grows, the factors necessary for optimum performance may more easily be delineated.

Edward J.C. Dawe, Orthopaedic Trainee, BASEM Member

This is a useful guide on drugs banned in sport and is particularly helpful when
travelling as it lists generic and trade names of drugs from 40 countries worldwide. Its
main disadvantages are that it does not list permitted drugs (unlike websites such as
100percentme) and it is only valid until the next WADA revision is released.

It can also be unclear at times, for instance oxymetazoline “used… to relieve nasal
and conjunctival congestion” is listed as “banned in competition”. It mentions later
that “topical use” is permitted. This led to momentary panic in a team sports situation
before it was clarified that oxymetazoline nasal spray is safe to use!

By Mark E Batt
Consultant Sport & Exercise Medicine
Fellow NHS Institute
President-elect Faculty of Sport & Exercise Medicine
Centre for Sports Medicine
Queens Medical Centre
Nottingham University Hospitals
Nottingham, UK

By Tony H. Reinhardt-Rutland, University of Ulster

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.

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-in-Chief,

We are concerned with an important confusion about data unit of measurement presented by Girard et al. when evaluating the changes in Lower Limbs Stiffness (LLS) during prolonged tennis playing (1). Evaluation of LLS is of great interest in a sport like tennis where speed and reactivity takes a great part. LLS is an important element of the muscle biomechanical characteristics and the optimal utilization of the stretch-shortening cycle requires some level of stiffness (2). Then an appropriate level of stiffness is necessary for optimal performance and prevention of injury (2). To evaluate LLS, Girard et al. used a standardized procedure proposed by Dalleau et al. (3). This method allows evaluation of LLS (expressed in N/m or in kN/m) in field conditions via the measure of both flight and contact times during a multi-rebound test.

Such a procedure has been previously used in several sport activities and results reported (4-5). However, in the article published by the British Journal of Sports Medicine, the results are presented expressed in N/m/kg while the correct unit is N/m or kN/m, as mentioned above. Comparison with the range of previous LLS data reported in the literature (4-5) confirms the confusion in the choice of unit by Girard et al. and suggests that it should likely be in kN/m. Although not affecting the conclusion of the authors concerning the relative changes in stiffness during prolonged tennis playing, we would like the scientists interested in LLS evaluation to be aware of this mistake in order to avoid a wrong interpretation of the data presented and to permit their use for comparison with other results.

By Sylvain Durand and Abdel Rahmani, Université du Maine, France.

A response to Hancock, Ste-Marie and Young (2008) by Joseph Baker and A. Jane Logan, York University.

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.

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.

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

Sir,

This is likely to be the definitive trial on the effectiveness of pre-exercise stretching for some time, so it is important that it is carefully reported and analysed in this paper by Jamtvedt et al. I have a few questions.

t is stated that “two primary outcomes and 12 secondary outcomes were specified a priori in the analysis plan” but only the two primary outcomes and five secondary outcomes appear in the paper. Four secondary endpoints (three reported in the paper) are listed in the trial protocol registered with the Australian and New Zealand Clinical Trial registry, accessible here. Five
secondary endpoints (three reported in the paper) are listed in the protocol available on the trial website, accessible here. In that protocol the second of the two primary endpoints (time to injury) is subdivided in a number of ways that, with the exception of whether the participant sought help from a professional, differ from the analyses reported.

The reported secondary analysis of “time to injuries to muscles, ligaments and tendons” differs from the pre-specified secondary outcome in both protocols of “time to injuries that might be considered could be preventable by stretching”? In the website protocol it is stated that this “preventability” classification would be done without knowledge of the trial group. Can the authors clarify whether this was done?

Can they also clarify which outcomes were pre-specified in the analysis plan before the trial allocation code was broken, can they report all these outcomes, and state what adjustment was made for multiple tests of statistical significance?

These questions may sound pedantic, but the primary outcome for injury was negative. The apparent effect on muscle ligament and tendon injuries was of only modest statistical significance (P=0.03), and might disappear if adjustment was made for multiple significance testing. The apparent effect on the “bothersome soreness” is unavoidably susceptible to reporting bias in an open trial. The higher rate of dropout from follow-up at all time points in the experimental group, which appears unlikely to be due to chance, might bias the results in either direction.

As a participant, I was impressed with the trial organisation and design. Without reassurance that analysis and reporting were of an equally high standard, I remain fearful that the authors’ conclusion that “stretching … probably reduces the risk of some injuries and does reduce the risk of bothersome soreness”, is too strong.

Jim Thornton
Nottingham
June 2009

This article relates the personal experience of a well-known Australian sports physician. Although thromboembolic events are reasonably uncommon among our athletes, flying is almost ubiquitous in our profession so this has more relevance than some of us might have anticipated when studying the clotting cascade in medical school.

Peter Brukner’s Personal Perspective from MJA