Effect of stretching on strength loss and pain after eccentric exercise

The purposes of the this study were to determine whether stretch-induced strength loss was muscle length dependent (study 1) and whether passive stretching prior to eccentric exercise affected strength loss and pain on subsequent days (study 2).

For study 1, knee flexion strength was measured isometrically (six angles) and isokinetically (eccentric and concentric) in 10 men (33 +/- 9 yr). The subjects then performed six 90-s static hamstring stretches, after which isometric and isokinetic strength were retested. For study 2, the dominant and nondominant legs of eight men (34 +/- 9 yr) were assigned to a stretch (six 60-s stretches) or control condition prior to eccentric hamstring exercise. Isometric strength and pain were assessed prior to, immediately after, and on the 3 d after exercise.

After stretching, strength was decreased by 17% at 80 degrees , 11% at 65 degrees , 5% at 50 degrees , 7% at 35 degrees , and 8% at 20 degrees , and it was increased by 6% at 5 degrees (angle effect P < 0.01). Strength loss following eccentric exercise was less on the stretched versus the unstretched control limb at 37 degrees (P < 0.05), but not at other angles (stretch by time by angle P < 0.01). Pain was not different between the stretched and the unstretched control limb (P = 0.94).

Stretch-induced strength loss was dependent on muscle length, such that strength was decreased with the muscle group in a shortened position, but not with the muscle group in a lengthened position. Strength loss and pain after eccentric exercise were generally unaffected by prior stretching, with the exception that stretching prevented strength loss when assessed with the muscle in a lengthened position.