To examine the effects of progressive relaxation (PR) on maximal muscle strength (MS) and power (MP), 7 trained varsity football players were tested for MS and MP following three experimental conditions: arousal (A), progressive relaxation (PR), and control (C). The arousal treatment involved exposure to a video of aggressive football play followed by assessment of MS (1-RM/lbs) and MP (3-Rm/lbs) accompanied by verbal encouragement, while PR and C conditions were followed by MS and MP assessment in the absence of verbal encouragement. The order of experimental treatments and assessments of MS and MP was randomized. ANOVA procedures indicated that PR significantly reduced pre-MS and pre-MP assessment of heart rate and blood pressure, as compared to A and C conditions. Maximal strength (MS) following PR (280 ± 12.6 [SE]) was significantly decreased as compared to MS following A (289.5 ± 11.9). In addition, PR resulted in a significant decrease in MP (253.5 ± 9.5 [SE]) as compared to both A (262.5 ± 9.3) and C (259.5 ± 9.4) conditions. The data suggest that PR may have a detrimental effect on the performance of athletes whose competition requires a significant reliance on muscle strength and/or power.