The primary objective of the present study was to examine the effects of three resistance training programs that varied in either inter-set rest interval length or volume of training on the development of strength and muscle fiber size. Male subjects with a minimum of 1- year of regular resistance training experience were randomly assigned to one of three, 8- week training groups. The first set of all three programs was similar in that 10 repetitions to failure were performed. In program A (n=5) the load (78% 1-RM) remained constant for all subsequent sets. Program B (n=7) also used a constant load (80% 1-RM), however the rest interval was reduced from 3 minutes (as in Program A) to 1 minute. Subjects in this group performed additional sets to equate training volume with Program A. The training load for Program C (n=7) was progressively reduced (80% to 70% 1-RM) before each subsequent set to ensure the completion of 10 repetitions. Therefore, the volume performed was greater than that of Programs A and B. Single arm elbow flexion 1-RM increased by 12.3 +/- 3.5% in Program A, 16.5 +/-3.5% in Program B, and 14.1 +/- 4.7% in Program C. Gains in 10-RM equaled 16.3 +/-4.1%, 18.0 +/- 5.0% and 13.9 +/- 3.1% for Programs A, B and C, respectively. Although these increases in strength were significant (p