Dissociation of training effects on skeletal muscle mitochondrial enzymes and myoglobin in man

The effect of endurance training on skeletal muscle myoglobin concentration in man was investigated. 8 healthy sedentary males (20–31 yrs) trained on cycle ergometers 40 min/day, 4 days a week for 8 weeks. The work consisted of continuous exercise at a work load that during the last 5 weeks corresponded to 75% of the pretraining maximal oxygen uptake (VO2 max). The training program resulted in a 7% increase in VO2 max (p<0.01). The activities of the mitochondrial enzymes citrate synthase (CS), succinate dehydrogenase (SDH) and cytochrome c oxidase (Cyt‐c‐ox) in the fluadriceps femoris muscle, as indicators of muscle respiratory capacity, increased by 62–82% (p<0.01). The metabolic adaptation of skeletal muscle was further indicated by a 17% increase in the work load corresponding to a blood lactate concentration of 4 mmol/1, as determined by a progressive exercise test (p<0.05). There was, however, no change in the myoglobin concentration of the thigh muscle with training (‐1%, NS). It is suggested that endurance exercise in man at 75% of the maximal oxygen uptake does not severely tax the functions of myoglobin in skeletal muscle.