Garrick and Webb1 in their excellent book, Sports Injuries: Diagnosis and Management, state that a weak muscle is a tight muscle. This concept is extremely important when we think of the causes and rehabilitation of muscle or musculotendinous strains.
They feel that overstretching of a muscle is not the chief cause of strain. It usually occurs by increased tension in the muscle before it has had time to lengthen, for example, by the sudden contraction of the antagonistic muscle before the agonist can lengthen. They point to the fact that most strains occur in the normal range of motion rather than the overstretched range. Because overstretching is often inappropriately considered the chief cause, treatment is mostly directed at improving flexibility of previously tight muscles. Whenever a weak muscle is forced to work beyond its capacity, it will tighten and, therefore, be more subject to stress and strain. It is imperative to always build the strength and endurance of muscles along with flexibility. A possible reason hamstring and adductor reinjury occurs is because too much attention is paid to stretching and not enough time is spent in strengthening. With injury and accompanying disuse atrophy, strength is always compromised. If flexibility is the main treatment, and strengthening is not included, the flexibility that is achieved will be temporary. The weak muscle will demonstrate inflexibility when maximum strength is required and be subject to micro and macro trauma. Strength is usually increased by lifting increasing amounts of weight, while endurance is increased by lifting lesser amounts of weight with more repetitions.
Muscle injuries are more often likely to happen during eccentric contraction. When eccentric contraction occurs, a muscle resists its own lengthening while the joint angle increases during the contraction. During maximum effort two times more muscle force is generated during eccentric over concentric contraction. Hamstring strains are likely to occur during the late forward swing phase (eccentric) when the hamstrings are decelerating thigh flexion and knee extension. A tear may result due to a difference in coordination between the contracting hamstrings and relaxing quadriceps.2 A tear may also result when the hamstrings switch from mid-support phase (knee stabilization) to hip extension and knee flexion at toe-off.
Reinjury of hamstring injuries is common in sports. Failure to reestablish hamstring strength and failure to use friction massage until the fibrotic deposits are eliminated are definite reasons for recidivism.
- Garrick, J.G.; Webb, D.R. Sports Injuries: Diagnosis and Management. Philadelphia, W.B. Saunders 1990; pp 7-25.
- Klafs, C.E.; Arnheim, D.D. Modern Principles of Athletic Training. 4th ed. Baltimore, Williams and Wilkins 1971.
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