David E. Martin

Relationship between energy deficits and body composition in elite female gymnasts and runners.

PURPOSE The purpose of this study was to evaluate energy balance and body composition in 42 gymnasts (mean age = 15.5 yr) and 20 runners (mean age = 26.6 yr), all of whom were on national teams or were nationally ranked. METHODS Athletes were assessed for body composition using DEXA and skinfolds, and energy balance was determined with a Computerized Time-Line Energy Analysis (CTLEA) procedure. RESULTS Results from the CTLEA were assessed as the number of within-day energy deficits (largest and frequency) and within-day energy surpluses (largest and frequency). There was a significant difference (P = 0.000) in the mean number of hourly energy deficits > 300 kcal experienced by gymnasts (9.45 +/- 6.00) and runners (3.70 +/- 5.34). There was also a significant difference (P = 0.001) in the mean number of hourly energy surpluses > 300 kcal experienced by gymnasts (1.40 +/- 3.04) and runners (6.20 +/- 5.50). The mean largest daily energy deficit was 743 (+/- 392) kcal for gymnasts and 435 (+/- 340) kcal for runners. The mean largest daily energy surplus was 239 (+/- 219) kcal for gymnasts, and 536 (+/- 340) kcal for runners. There was a significant relationship between the number of daily energy deficits > 300 kcal and DEXA-derived body fat percent for gymnasts (r = 0.508; P = 0.001) and for runners (r = 0.461; P = 0.041). There was also a negative relationship between the largest daily energy surplus and DEXA-derived body fat percentage for gymnasts (r = -0.418; P = 0.003). Using the energy balance variables, age, and athlete type (artistic gymnast, rhythmic gymnast, middle-distance runner, long-distance runner) as independent variables in a forward stepwise regression analysis, a small but significant amount of variance was explained in DEXA-derived (P = 0.000; R2 = 0.309) and skinfold-derived (P = 0.000; R2 = 0.298) body fat percent by the number of energy deficits > 300 kcal and age. CONCLUSIONS These data suggest that within-day energy deficits (measured by frequency and/or magnitude of deficit) are associated with higher body fat percentage in both anaerobic and aerobic elite athletes, possibly from an adaptive reduction in the REE. These data should discourage athletes from following restrained or delayed eating patterns to achieve a desired body composition.

Effects of a functional knee brace for ACL insufficiency during treadmill running.

PURPOSE To assess the effects of a functional knee brace (FKB) for anterior cruciate ligament insufficiency (ACLI) on physiological and perceptual parameters during treadmill running. METHODS Thirteen ACLI subjects (time since injury, 5.8 +/- 5.3 yr), performed an incremental test to exhaustion and two constant load 20-min tests, one at an intensity below lactate threshold (bLT), and the other at an intensity above LT (aLT) each with and without their FKB. RESULTS Bracing had no effect on peak variables except for higher ratings of perceived exertion at the legs (RPE-L) at the velocities associated with a blood lactate concentration [HLa] of 4.0 mM and at peak. Bracing had no effect when exercising at bLT but did significantly alter the metabolic profile developed during the performance of the aLT tests (83 +/- 0.03% VO2peak). In particular, FKB resulted in elevated blood [HLa] (23%), VO2 (4%), VE (12%), VCO2 [corrected] (7%), and VE/VO2 (7%). HR and slow component VO2 did not differ between the brace and no brace aLT tests. RPE-L and RPE-knee were significantly elevated during aLT when the brace was worn. Suspected mechanisms include alterations in muscle recruitment patterns and/or occlusion. CONCLUSIONS When ACLI individuals wear a FKB during high intensity straight-ahead running exercise of long duration, physiological parameters are affected.