Saturday, March 03, 2007


clipped from
Two randomized studies[2,3] investigating the effect of stretching before the main exercise session concluded that this did not decrease injury risks. Regarding the reduction of delayed onset muscular soreness (DOMS), only one study observed reduction in soreness;[4] however, this occurred 72 hours after maximum eccentric knee flexion. Results from this study should be interpreted with caution because, not only did it take a long time for the beneficial effects to be noticed, but the sample size was also very small (ten females). Recent reviews[5-9] have suggested that stretching exercises do not protect against injury, nor do they diminish DOMS or enhance performance.
Various studies, with total stimuli duration varying from 120 to 3600 seconds, found that stretching exercises preceding the main strength activity significantly decreased performance.[10-30]
Decreases in strength ranged from 4.5% to 28%, irrespective of the testing mode
In contrast to these results, other authors[35-40] did not observe any detrimental effects of stretching on strength. The total stimuli duration in these studies was shorter, ranging from 30 to 480 seconds.

Flexibility and strength are fitness components that are fundamental in many sports modalities and even for common daily motor tasks. Training for flexibility and strength is widely recommended for those who wish to attain good fitness levels and a better quality of life. Many activities rely heavily on strength, but strength performance may be diminished by a preceding stretching routine; therefore, it is important to understand this phenomenon when prescribing physical exercise programmes. There appears to be substantial evidence suggesting a decrease in strength following stretching. Studies used different stretching techniques, duration and targeted different muscle groups, and were tested with isotonic, isometric or isokinetic devices. However, the number of exercises, duration of each exercise and number of sets (i.e. the total duration of stretching) was much longer than the ranges normally used in practice and what is recommended in the literature. This makes evident the need for further studies with designs that do not threaten their external validity. Training studies should also be conducted in order to assess whether the decreases in strength observed during the training session will have long-term consequences (i.e. suboptimal gains in strength when compared with training without prior stretching).

Furthermore, the safety of the participants should be taken into consideration in the recommendation of stretching exercises. When the possible effects of these exercises are analysed, it seems that many of the mechanisms responsible for maintaining the myo-osteo-articular integrity, such as muscle, tendon and joint receptors, are inhibited following stretching. Tolerance to pain also seems to be increased, allowing range of motion to be greater and closer to the maximal limit of the stretched structures, and consequently, closer to injury risk. The hypothesis that flexibility exercises preceding other physical activities may lead to greater injury risks should be considered and investigated in future studies.

Many mechanisms underlying stretching exercises still demand investigation so that links between the observed effects, their causes and consequences may be constructed.

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