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1st Jun


Overuse Injuries: Often Imbalance Between Work and Rest

Our skeletal muscles contract to support and move our bodies, and they also store energy. There is a certain amount of energy store available for each of us, on a daily basis. The world renowned exercise physiologist Per Olof Astrand and others have described that the body keeps an energy reserve of 70% of its total energy, leaving 30% of the total energy store for work, activities of daily living, and exercise (Rivard and Grimsby, 2009). The energy reserve is used for tissue recovery and repair, by building up or regenerating tissues.

If we consistently use more than the 30% of the total energy on a daily basis for activities and exercise, the available energy reserve decreases, and we experience tissue breakdown, or degeneration, leading to painful conditions and overuse injuries. This is believed to be the most common cause of injuries in sports, and the optimal amount of rest needed remains the most difficult aspect of sports training to determine with certainty. This is typically more important than the training itself, since the work and exercise temporarily breaks down tissues, and it is the rest after exercise which increases our fitness and performance.

Tapping into too much of the energy reserve may also accelerate degenerative processes, such as joint osteoarthritis and spinal disc degeneration. It is the tissues with low metabolism that are affected the most, such as tendons, cartilage in joints, and intervertebral discs. When tendons are involved, we develop tendinopathy or tendinosis, in the past referred to as “tendinitis”.

The total energy available varies with age, fitness level, and after illness or surgery. To promote health and prevent overuse injuries and tissue degeneration, the type and amount of work, and the amount of rest, must be planned accordingly. As we age, we lose muscle fibers and the amount of energy reserve available to us. Therefore, if we continue with the same level of daily activity in our 50s and 60s, as we did in our 20s and 30s, we easily start to derive energy required for such activity from the reserve, normally used for recovery and tissue maintenance. As a result, not enough energy is left to rebuild tissues, which therefore start to break down. Age related loss of muscle mass and energy can be reduced by improving our fitness level.

The type of exercise also determines how much energy we expend. High intensity strength training and power training are the most taxing, and although training sessions may be relatively short, there must be sufficient rest during and after sessions. As an example, plyometric training shall typically not be performed more than 1-2 times per week. Lower intensity, endurance type exercise, such as bicycling, swimming and jogging may for the trained individual be performed for longer periods and perhaps even daily, without tapping into the reserve energy store.

In order to prevent overuse injuries as we age, it would be recommended to reduce the exercise intensity, rest more between exercise sessions, and even reduce the total volume of work performed.

This information is important in particular for us aging baby boomers, who as a group are more active than past generations. Please feel free to call us, if you or someone you know want to determine the optimal exercise-rest ratio for you, or if you may have tapped into your energy reserve, and you need help to reduce your pain and regenerate tissues.

Best wishes for continued good health,


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