Body system chronic adaptations to training.
This article examines adaptations to regular exercise over an extended period of time in the skeletal and the muscular systems, using the example of Nathan doing three rides and one circuit training session per week for six months.
Skeletal system adaptations;
Strengthening of the bone occurs when bones are subjected to mechanical loading. The circuit training and the hard interval riding would produce the ideal stimulus for this adaptation in Nathan’s leg bones. Following the principle of progressive overload the bones must be stressed but without risking stress fractures.
Strengthening of the joint synovial capsule occurs under the same stress conditions and simultaneously with the above.
Thickening of the elastic hyaline cartilage layers at the ends of the bones within the joint capsule is stimulated by Increased movement of a joint. Moderate aerobic exercise is the trigger, which Nathan does on his longer rides, and the greatest affect would be to his ankles, hips, and knees.
Strengthening of the ligaments occurs in a way similar to the bone strengthening described above. This results in a joint that is more resilient to friction from Nathan’s aerobic endurance riding.
Note: Long term studies in various different athletes have shown swimmers and long distance cyclists to have bone mineral density loss approximately the same as the general population. This is because unless stressed the bones lose their strength. Variation and high intensity intervals of sprints and hill climbs help. However cyclists will benefit by including some impact exercise in their training, examples include jogging, skipping and even dancing.
Muscular system adaptations;
The following adaptations result from prolonged anaerobic training such as Nathan’s circuit training;
Increased number and density of myofibrils. In a trained muscle new lengths of protein are laid down to the outside of the existing structure thus increasing the number available to contract. Consequently the cross-sectional area of the myofibril is increased, known as hypertrophy, and it becomes stronger. Type II muscle fibres hypertrophy more markedly than type I.
Calcium release into the sarcoplasm, has been shown to increase from sprint training, which it is reasonable to suppose Nathan will include in his circuit training.
The following adaptations result from prolonged aerobic training such as Nathan’s thrice weekly riding;
Increased number of mitochondria, which contain myoglobin and makes it available to oxidise glycogen for ATP production.
Stores of triglycerides and glycogen, and the enzymes that metabolise them increase, within the mitochondria, extending the time Nathan will be able to ride for.
Type IIx muscle fibre adapts to become Type IIa fibre, which has the highest oxidative capacity of all Type II fibres and makes a significant aerobic contribution. It This adaptation is unusual in the sense that it is stimulated by aerobic and anaerobic training at high intensity which Nathan’s training regime accommodates.
The next “Coaching Corner” article will examine how this theory can be applied to coaching practice.
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