In girls only, significant relationships between maturity and indices
of anaerobic metabolism were noted. The lack of relationship in the boys is likely to have been due to the boys being pre-pubertal or early pubertal. Kuno et al.72 selleck chemicals studied the responses of 12–15-year-old boys and adults to quadriceps exercise to exhaustion and during recovery. They reported higher values of PCr/(PCr + Pi) and pH at exhaustion in the boys than in the men and concluded that both the trained and untrained boys had, “less glycolytic ability during exercise than adults”. During recovery the PCr kinetics τ was shown to be invariant with age indicating similar oxidative capacity in boys and men. 73 In conflict with these findings Taylor et al. 74 AZD9291 reported a faster re-synthesis of PCr in children during recovery from calf muscle exercise to exhaustion and concluded that the oxidative capacity of skeletal muscle is highest in children. However, the interpretation of recovery data from both of these studies is confounded by the reported low muscle pH values with adult pH values significantly lower than those of children. In
a more recent study involving finger flexion exercise, Ratel et al. 75 reported similar end-exercise pH values in adults and 11-year-old boys but a faster PCr τ in the boys during recovery. In accord with Taylor they concluded that their results clearly illustrated a greater mitochondrial oxidative capacity in the boys than in the men. The effects of maturation
on exercise metabolism were investigated by Petersen et al.76 who evaluated the responses of nine pre-pubertal and nine pubertal swimmers to 2 min of calf exercise at 40% of pre-determined maximal work capacity (MWC) followed by 2 min at 140% of MWC. At end-exercise the Pi/PCr was higher and the pH lower in the pubertal girls but the differences were not statistically significant. This inferred that glycolytic metabolism was not age or maturity dependent but others this conclusion needs to be interpreted cautiously as the difference between the two groups in Pi/PCr at end-exercise was 66% and the high individual variability and small sample size suggest that this might have biological significance. Using an experimental design in which seven pre-pubertal boys and 10 men performed finger flexion exercise against a resistance of 15% of maximal voluntary strength, Tonson et al.77 investigated muscle energetic changes with maturation. They observed the total energy cost to be similar in both groups but the interplay of metabolic pathways to be different. At the onset of exercise the boys exhibited a higher oxidative contribution to ATP re-synthesis and a lower PCr breakdown than the men.