The effects of isometric versus isotonic exercise programs in the restoration of strength to the quadriceps femoris following injuries to the knee was studied in 72 men, ages 17 to 41 years. The duration of treatment necessary, increase in strength, cross-education and muscular hypertrophy were noted. On 5 days each week, 10 isotonic contractions were performed at 50%, 75 percent and 100% of maximum starting from 75 degrees of flexion and from 45 degrees of flexion. Three six-second isometric contractions at 45 degrees of flexion and at full extension were performed in the isometric series. Strength was measured by one repetition maximum (RM) and 10 to RM tests. Thigh circumference was measured 4 inches above the patella. Statistical analyses showed that patients on the isotonic routine received an average of 13.7 treatments while those on the isometric routine received 10.6 treatments, a difference statistically significant at the 5 percent level of probability. There was no significant difference for increase in strength as measured by the 10-RM or the 1-RM test. There was no evidence of cross-education or muscle hypotrophy. It was concluded that the isometric routine allows more rapid rehabilitation of the injured knee than the isotonic routine.

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