Changes in Muscular Strength Over a 24-Week Cycle Ergometer Interval Program

Abstract

Little is known about the how an intensive aerobic interval training program would influence muscular strength in healthy adults aged 30-62. PURPOSE: To determine if participation in an intensive interval exercise program targeted towards increasing aerobic fitness could lead to gains in muscular strength. METHODS: Participants completed a 6-day per week exercise program on a cycle ergometer for a 6-month time period. Participants were healthy adults (M age = 46.90, SD = 7.40, n = 19) who self-reported participating in at least 30 minutes of vigorous exercise, 3 times per week. Subjects exercise 6 days per week, using the complete aerobic routines developed by Ploutz-Snyder that consisted of (a) 30 min. of continuous aerobic exercise on a stationary cycle at or above 75% of maximum heart rate, (b) long, 4 x 4 min. intervals at or above 90% maximum heart rate with 3 minutes active rest, (c) medium 6 x 2 min. intervals at 70%, 80%, 90%, 100%, 90%, 80% of maximum heart rate, respectively with 2 minutes active rest, and (d) short 30 sec. sprint intervals at maximal effort with 20 sec. active rest. Other physical activities outside the lab were tracked and recorded, and participants did not report engaging in any strength training during the study. Isometric knee strength (45deg, 5sec contraction) was measured on the right leg before and after the 6-month training program using the Biodex 3 dynamometer. Peak Torque Flexion (PTF) and Peak Torque Extension (PTE) were measured and compared pre and post the 6-month program. A dependent t-test was used to calculate differences pre to post. RESULTS: PTF on average significantly increased from the pre-test to the post-test (92.67±28.53 ft/lbs vs. 102.19±29.02 ft/lbs, t = 2.37, p = 0.03, Cohen’s d = 0.56). PTE did not differ statistically from the pre test to the post test (61.59±18.62 ft/lbs vs. 60.34±21.98 ft/lbs, t = -0.58 p = 0.57, Cohen’s d = 0.14). CONCLUSION: Interval training appears to be a viable option for increasing some measures of muscular strength over a 6-month training period. This finding suggests that healthy, middle aged subjects can achieve muscular strength benefits from very short, high-intensity aerobic intervals. Grant: NASA/National Space Biomedical Research Institute, MA03401