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1st Mar

2020

Overuse Injuries: Often Imbalance Between Work and Rest

I’ve decided to resend a newsletter from 2011, which I think is a very important topic for anyone who is involved in exercise, especially as we age, or if we have sustained a significant injury or suffered illness. It is also of utmost importance in sports training and for those who engage in intense training, and it remains perhaps the most difficult component of elite sports training, to plan, analyze and tweak during the scope of a season, in order for the athlete to recover sufficiently and peak at the right time, and to prevent injuries and even illness in endurance sports (due to suppressed immune function as a result of over training). Athletes in all age groups are familiar with the term sports periodization, which refers to alternating cycles of training throughout the year, and which includes progressive increases in training intensity and/or duration, followed by periods of lighter recuperation periods, in particular prior to major sporting events.

However, the balance between work and rest goes way beyond sports, and plays an essential role in keeping us healthy and free of pain and injury in daily life. Here is how I described it:

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 doesn’t mean that, if we are fit, we can’t train with intensity even in our 60s and 70s, but it does mean that it becomes easier to tap into our energy reserve as we age, and therefor it becomes increasingly more important to get sufficient rest as part of our training routine and daily life.

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