Physiological response during running in athletes with similar body mass but different body composition

Assessing body composition in rugby players: agreement between different methods and association with physical performance

BACKGROUND

This study investigated the comparability between air displacement plethysmography (ADP), dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance analysis (BIA) methods for body composition assessment and their correlations with physical performance in rugby players.

METHODS

Nineteen male elite players participated in the study. ADP, DXA, and BIA were used to assess fat-mass and fat-free mass. Physical performance was assessed by means of Carminatti's test of peak velocity (PVTCAR), countermovement jump (CMJ), sprint speed (10 and 30-m), and match performance analyses (sprinting, distance covered, and high-intensity running).

RESULTS

BIA overestimated fat-mass (13±41%; r2=0.60) and underestimated fat-free mass (-1±7%; r2=0.66) compared to ADP (P=0.001). BIA underestimated fat-mass (-28±3%; r2=0.92) and overestimated fat-free mass (10±5%; r2=0.87) compared to DXA (P<0.001). ADP underestimated fat-mass (-36±37%; r2=0.69) and overestimated fat-free mass (11±8%; r2=0.52) compared to DXA (P<0.001). Fat-mass measured by ADP, DXA, and BIA negatively correlated with PVTCAR (r2≥0.49), height and peak power from CMJ (r2≥0.30), sprinting ability (r2≥0.65), and match performance variables (r2≥0.30).

CONCLUSIONS

As long as one considers that ADP and BIA underestimated fat-mass and overestimated fat-free mass compared to DXA, the methods can be used to estimate body composition, particularly to track body fat-mass changes, which negatively influence several physical capacities determinant to rugby performance. The limitations of the methods should be borne in mind when assessing the body composition of rugby athletes.

Lower Leg Length is Associated with Running Economy in High Level Caucasian Distance Runners

The aim of the present study was to investigate lower limb anthropometric and composition variables related to running economy (RE) and running performance in a homogeneous group of high level European distance runners. RE at the speeds of 14, 16 and 18 km·h⁻¹ (189 ± 12; 188 ± 11; 187 ± 11 O₂ ml·kg⁻¹·km⁻¹) and maximal oxygen uptake (VO_2max) (67.3 ± 2.9 ml·kg⁻¹·min⁻¹) of 13 high level distance runners were determined on a motorised treadmill. Anthropometric variables and body composition were measured. The BMI was related to RE at the speed of 14 (r² = 0.434; p = 0.014), 16 (r² = 0.436; p = 0.014) and 18 km·h⁻¹ (r² = 0.389; p = 0.023). Lower leg length was negatively related to RE at the speed of 16 and showed such a tendency at the speed of 14 and 18 km·h⁻¹. VO_2max indicated a moderate relationship with RE at the speeds of 14, 16 and 18 km·h⁻¹ (r² = 0.372, p = 0.030; r² = 0.350, p = 0.033; r² = 0.376, p = 0.026, respectively) which was confirmed by subsequent partial correlation analysis. While lower leg length and the BMI presented a relationship with RE, none of the calculated body composition and anthropometric proportions were related to RE or performance. The relationship between RE and VO_2max would confirm the notion that RE could be at least partly compensated by VO_2max to achieve high performance results.