There has been much debate about skeletal muscle capacity to adapt to long-lasting
endurance exercise. Exercise in the aerobic zone of metabolism does not result in
hypertrophy of skeletal muscle fibres but increases their oxidative capacity. The
duration and intensity of an exercise session determines the time period of depressed
muscle protein synthesis and increased degradation rate during the recovery period
after exercise. Protein turnover characterizes the renewal processes of muscle proteins
and the functional capacity of muscle. The turnover rate of myofibrillar proteins
is slow in comparison with mitochondrial proteins and depends on the oxidative capacity
of muscle fibres. The turnover rate of myofibrillar proteins in the same muscle is
different and is also different within the myosin molecule between myosin heavy and
light chain isoforms. The turnover rate of muscle proteins in endurance training shows
the adaptation of skeletal muscle to long-lasting exercise via remodelling of muscle
structures. Adaptational coordination between myofibrillar and mitochondrial compartments
shows the physiological role and adaptational capacity of skeletal muscle to endurance
training. It is challenging to use muscle protein turnover for the purposes of monitoring
the training process of endurance athletes, optimizing training programs and preventing
overtraining.
Key words
endurance training - skeletal muscle - oxidative capacity - protein turnover
