Objective: The present study analysed the allometric relationship (MR = a . M(b)) between human metabolic rate (MR), ranging from resting to maximal metabolic conditions, and body mass (M ), both in athletes of different specialization and untrained individuals.
Subjects and methods: Two hundred and seventy male athletes and 43 untrained men performed a continuous incremental test to volitional exhaustion on a motorized treadmill. Metabolic rate (i.e. VO2) was measured during resting (VO2REST), sub-maximal (walking at 5 km h(-1) VO2WALK; running at 7.5 km h(-1) VO2RUN; ventilatory anaerobic threshold VO2VT) and maximal exercise conditions (maximum oxygen uptake VO2MAX).
Results: A significant difference (p < 0.001) in the MR-body mass relationships between athletes and controls was found. For the control group, the mass exponent b exhibited a non-significant (p = 0.37) increase with increasing metabolic demand (b = 0.69, 0.76, 0.76, 0.84, and 0.89, for VO2REST, VO2WALK, VO2RUN, VO2VT, and VO2MAX, respectively). In contrast, the corresponding mass exponent for the athletic group significantly (p < 0.01) decreased when moving from resting to maximal metabolic conditions (b = 0.98, 0.88, 0.80, 0.69, and 0.67).
Conclusion: These results indicate that the recently proposed allometric cascade model may be valid in describing the scaling behaviour of MR in untrained individuals, but not in athletes of different specialization.