Effect of rest duration between sets on fatigue and recovery after short intense plyometric exercise

Abstract

Plyometric training is characterized by high-intensity exercise which is performed in short term efforts divided into sets. The purpose of the present study was twofold: first, to investigate the effects of three distinct plyometric exercise protocols, each with varying work-to-rest ratios, on muscle fatigue and recovery using an incline-plane training machine; and second, to assess the relationship between changes in lower limb muscle strength and power and the biochemical response to the three exercise variants employed. Forty-five adult males were randomly divided into 3 groups (n = 15) performing an exercise of 60 rebounds on an incline-plane training machine. The G0 group performed continuous exercise, while the G45 and G90 groups completed 4 sets of 15 repetitions, each set lasting 45 s with 45 s rest in G45 (work-to-rest ratio of 1:1) and 90 s rest in G90 (1:2 ratio). Changes in muscle torques of knee extensors and flexors, as well as blood lactate (LA) and ammonia levels, were assessed before and every 5 min for 30 min after completing the workout. The results showed significantly higher (p < 0.001) average power across all jumps generated during intermittent compared to continuous exercise. The greatest decrease in knee extensor strength immediately post-exercise was recorded in group G0 and the least in G90. The post-exercise time course of LA changes followed a similar pattern in all groups, while the longer the interval between sets, the faster LA returned to baseline. Intermittent exercise had a more favourable effect on muscle energy metabolism and recovery than continuous exercise, and the work-to-rest ratio of 1:2 in plyometric exercises was sufficient rest time to allow the continuation of exercise in subsequent sets at similar intensity.

Keywords: Ammonia; Lactate; Muscle torques; Peak power.

Figure 1

Characteristics of the mean peak power generated in successive sets of exercise relative to body mass (W/kg). The arrows indicate in which subsequent sets of exercise the power values were significantly lower than in the first one. **p < 0.01 ***p < 0.001—values significantly lower than in the first set. ^ap < 0.05—values significantly lower than in G45 and G90.

Figure 2

Changes in knee extensors muscle torques (Nm) before exercise (pre) and in the successive 7 measurements taken every 5 min after exercise. The arrows indicate the range of measurements in which muscle torque values remained significantly lower than pre-exercise (***p < 0.001).

Figure 3

Changes in lactate levels (mmol/l) before exercise (pre) and in the successive 7 measurements taken every 5 min after exercise. The arrows indicate the range of measurements in which lactate concentration remained significantly higher (p < 0.001) than pre-exercise. *p < 0.05, **p < 0.01, ***p < 0.001—values significantly higher than pre-exercise.

Figure 4

Changes in ammonia levels (μmol/l) before exercise (pre) and in the successive 7 measurements taken every 5 min after exercise. The arrows indicate the range of measurements in which ammonia concentration remained significantly higher (p < 0.001) than pre-exercise. *p < 0.05, **p < 0.01, ***p < 0.001—values significantly higher than pre-exercise. ^ap < 0.05—values significantly higher than in groups G45 and G90.

Figure 5

The sequence of the example bounce on the training machine.

Figure 6

Time course of the experiment.