Effects of Different Tempos of a Side-step Interval Exercise on Heart Rate and Muscle Activation

Abstract

One barrier to meeting fitness recommendations may include time constraints. Finding exercises that can promote improvements in both aerobic and muscular fitness while minimizing the duration of the exercise and the required equipment are needed. One such exercise may be the side-step interval exercise. Currently, it is unknown how different tempos influence this exercise and how heart rates and muscle activation differ between tempos. PURPOSE: To investigate how different tempos of a side-step interval exercise influence heart rate and muscle activation responses. METHODS: Recreationally active men (n=8) and women (n=2) participated in this study. The average maximum oxygen uptake (VO2max) of participants was 50.1 ± 10 yrs and age was 21 ± 3 yrs. The side-step interval exercise consisted of moving from side to side repetitively over a two-meter distance for 1 minute with 1-minute rest periods in between sets. Four sets of these exercise intervals were performed. The fast (112 bpm) or slow (84 bpm) tempo was randomly assigned during the first exercise session with the other tempo being used in the next visit. Surface electromyography (EMG) measured muscle activation of the vastus lateralis and a heart rate monitor (Polar) measured heart rate (HR). Two-way repeated measures ANOVA analyzed differences between tempos and sets. Pearson product moment correlations analyzed associations between VO2max, HR response and muscle activation. Statistical significance was set at p<0.05. RESULTS: Slow tempos produced significantly lower amounts of muscle activation compared to the fast tempos [46% vs. 59% of the maximum isometric voluntary contraction muscle activation (EMGmax), p=0.002]. HR significantly increased at the end of sets 3 (150 ± 8 bpm, p=0.012) and set 4 (152 ± 8 bpm, p=0.001) when compared to set 2 (146 ± 8 bpm). The fast tempo produced significantly greater HR than the slow tempo (82% HRmax vs. 70% HRmax, p<0.001). A significant inverse relationship was also found between VO2max and vastus lateralis muscle activation (r=-0.855, p=0.003), fast tempo HR (p=-0.896, p<0.001) and slow tempo HR (p=-0.924, p<0.001). CONCLUSIONS: Side-step interval exercise acutely produces sufficient levels of HR and muscle activation to promote improvements in aerobic and muscular fitness but future chronic studies are needed.