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Abstract.
Burgess, K.E., M.J. Connick, P. Graham-Smith, and S.J. Pearson. Plyometric vs. isometric training influences on tendon properties and muscle output. J. Strength Cond. Res. 21(3): 986-989. 2007.-The purpose of this study was to concurrently determine the effect that plyometric and isometric training has on tendon stiffness (K) and muscle output characteristics to compare any subsequent changes. Thirteen men trained the lower limbs either plyometrically or isometrically 2-3 times a week for a 6-week period. Medial gastrocnemius tendon stiffness was measured in vivo using ultrasonography during ramped isometric contractions before and after training. Mechanical output variables were measured using a force plate during concentric and isometric efforts. Significant (p < 0.05) training-induced increases in tendon K were seen for the plyometric (29.4%; 49.0 ± 10.8 to 63.4 ± 9.2 N.mm^sup -1^) and isometric groups (61.6%; 43.9 ± 2.5 to 71.0 ± 7.4 N.mm^sup -1^). Statistically similar increases in rate of force development and jump height were also seen for both training groups, with increases of 18.9 and 58.6% for the plyometric group and 16.7 and 64.3% for the isometric group, respectively. Jump height was found to be significantly correlated with tendon stiffness, such that stiffness could explain 21% of the variance in jump height. Plyometric training has been shown to place large stresses on the body, which can lead to a potential for injury, whereas explosive isometric training has been shown here to provide similar benefits to that of plyometric training with respect to the measured variables, but with reduced impact forces, and would therefore provide a useful adjunct for athletic training programs within a 6-week time frame.
KEY WORDS, tendon stiffness, rate of force development, exercise
Introduction
Previous studies have shown that rate of force development (RFD) has a significant relationship with sporting events requiring high-power output (22, 24). During these dynamic explosive activities, there is a limited amount of time available to produce force, and therefore, the rate at which force is generated becomes very important. To develop force, a muscle must first take up the slack within the tendon. Therefore, a tendon that is less stiff would result in an increased time in which to develop force. Rate of force development has been seen to increase after relatively short periods of...