A test of the maximum-power stimulus theory for strength.

The main purpose was to test the hypothesis that the true force and power in weightlifting were related significantly to the strengthening stimulus. Secondary hypotheses were (a) slower, heavier weight training for strength would increase strength, not maximum power, (b) faster, lighter weight training for maximum power would increase maximum power, not strength and (c) there would be no significant difference between force = mass (F = m) and true force = mass multiplied by acceleration (F = ma) for arm weightlifting. Using an optical encoder, digital recorder and a data-logging computer on an arm weightlifting machine, F = m and F = ma were significantly different between 25% and 94%, contrary to published reports, but not at 100% of strength. A second-order polynomial equation predicted force, F = ma, as a multiple of the weight lifted, from the velocity of the lift with R2 = 0.997. A group was trained for strength and a matched group was trained for maximum power. The strength group gained significantly in maximum power and the power group gained significantly in strength and maximum power. Both groups gained significantly in velocity, but not force, at maximum power. The correlations between strength and maximum power were high (r = 0.95-0.98, P < 0.02), consistent (before and after training) and valid (gain in standard error of estimate of 6 N or 2% of strength). The evidence suggested that maximum power was the strength stimulus. The maximum-power stimulus theory may unify and simplify theories of response and adaptation of structure and function induced by muscle.