JOURNAL WATCH

GROUND REACTION FORCE DIFFERENCES BETWEEN RUNNING SHOES, RACING FLATS AND DISTANCE SPIKES IN RUNNERS. Logan S, Hunter I et al. Journal of Sports Science and Medicine 2010;9:147–153

This study measured the differences in ground reaction forces between running shoes, racing flats, and distance spikes in order to provide information about the potential effects of footwear on injury risk in highly competitive runners. Ten male and ten female intercollegiate distance runners ran across a force plate at 6.7 m·s-1 (for males) and 5.7 m·s-1 (for females) in each of the three types of shoes. To control for differences in foot strike, only subjects who exhibited a heel strike were included in the data analysis. For the males, loading rate, peak vertical impact force and peak braking forces were significantly greater in flats and spikes compared to running shoes. Vertical stiffness in spikes was also significantly greater than in running shoes. Females had significantly shorter stance times and greater maximum propulsion forces in racing flats compared to running shoes.

sportEX comment Proof, if anyone that works in athletics needs it, that different shoes alter the loads placed on the body. The peak time for injury prevention strategy is when the shoes are changed during different phases of training. Acclimatisation to the changeover may reduce the risk.

DIAGNOSING OVERTRAINING IN ATHLETES USING THE TWO-BOUT EXERCISE PROTOCOL. Meeusen R, Nederhof E et al. British Journal of Sports Medicine 2010;44:642-648

This study looked for an immediate and objective distinction between non- functional over-reaching (NFO) and overtraining syndrome (OTS). Ten underperforming

athletes. who were diagnosed with the suspicion of NFO or OTS were studied. NFO was retrospectively diagnosed in five athletes, and OTS in five athletes. A two-bout maximal exercise protocol was used to measure physical performance and stress-induced hormonal reactions. Recovery of the athletes was monitored by a sports physician to retrospectively distinguish NFO from OTS. Exercise duration, heart rate and blood lactate concentration were measured at the end of both exercise tests. Venous concentrations cortisol, adrenocorticotrophic hormone (ACTH), prolactin and growth hormone were measured before and after

both exercise tests. The results showed that maximal blood lactate concentration was lower in OTS compared with NFO, while resting concentrations of cortisol, ACTH and prolactin concentrations were higher. However, sensitivity of these measures was low. The ACTH and prolactin reactions to the second exercise bout were much higher in NFO athletes compared with OTS and showed the highest sensitivity for making the distinction.

sportEX comment This shows some promise. NFO might be distinguished from OTS based on ACTH and prolactin reactions to a two-bout exercise protocol but it is a fairly small sample size and probably needs to be extended to prove the results.

OVERTIME WORK AND INCIDENT CORONARY HEART DISEASE: THE WHITEHALL II PROSPECTIVE COHORT STUDY. Virtanen1 M, Ferrie J, et al. European Heart Journal 2010;10:1093 (First published online: May 11)

Six thousand and fourteen British civil servants (4262 men and 1752 women), aged 39–61 years who were free from coronary heart disease CHD and worked full time at baseline (1991–1994), were followed until 2002–2004, an average of 11 years. The outcome

measure was incident fatal CHD, clinically verified incident non-fatal myocardial infarction (MI), or definite angina (a total of 369 events). Analysis showed that 3–4 hours overtime work per day was associated with 1.60-fold increased risk of incident CHD compared with employees with no overtime work. Adjustment for all 21 cardiovascular risk factors measured made little difference to these estimates This association was replicated in multivariate analysis with only fatal cardiovascular disease and incident non-fatal MI as the outcome.

sportEX Comment If you work in sport the chances are that you clock up more than a standard 35 hours

a week. In fact it is not unusual in professional elite sport especially cricket and football for practitioners to work double that and to do so for weeks at a time without days off. The really scary bit of this study is that the conclusion that overtime work is related to increased risk of incident CHD independently of conventional risk factors. You have been warned!!!!

6

sportEX dynamics 2010;26(Oct):4-6