(1) Existing data on oxygen or energy requirement and speed have been analysed, using the formula E=KVn, where E denotes oxygen or energy requirement at speed V, and K and n are constants.(2) Comparison of several forms of muscular exercise or work, showed that the value of n is correlated to the severity of muscular activity.(3) If a given muscular exercise shows optimal speed, n has two distinctly different values, on both sides of the optimum.(4) Resistance of muscular movement is briefly discussed, and the possibility of utilization of momentum by the body has been pointed out.