Between set rest is an important training variable. The duration of the rest interval influences which energy systems are prioritized and the capacity of future lifts. If you are targeting strength and power, it is advisable to use long rest breaks (>3 minutes). If you are targeting endurance and aerobic condition, little to no rest is implemented (<30 seconds). Hypertrophy falls in the middle (1-2 minutes). What should you do during that time? Traditionally, you want to perform the minimal activity needed to maximize recovery. You may implement mental imagery to prepare for the next set (common in strength sports) or use the time for reflection on a previous effort. We are seeing more evidence assessing the potential impact of other strategies, such as aerobic exercise, heating and cooling, stretching, vibration, self-massage and foam rolling, individual heart rate (HR)-based intervals, posture-related positioning, and electromyostimulation. These strategies aim to expedite recovery and enhance subsequent performance. This systematic review examined current evidence on interset interventions and evaluated their effect on acute resistance training performance and associated physiological responses.
The final review included 26 studies that assessed all the previously mentioned interest strategies. Of the 7 stretching studies, 2 showed an increase in repetitions performed by the stretching group while 1 showed a reduction in contraction velocity (power output). The evidence suggests the best approaches to increase the number of repetitions you can perform on the next set may be dynamic stretching or statically stretching the antagonist muscle (the opposite of the one being worked, such as stretching the hamstrings between leg extension sets which targets the quadriceps). For enhancing muscle growth, other research suggests agonist stretching is needed, but we don’t have a lot of data.
Of the 6 studies that assessed the effectiveness of heating a cooling, 5 tested the number of repetitions performed after the interest intervention, and 4 of those found improvements. The studies primarily assessed the cooling of the upper extremities. Cooling may improve reflexes, increase muscle excitability, increase the release of neurotransmitters, and reduce ratings of perceived exertion. The evidence on heat is sparse, limiting the ability to draw conclusions.
Aerobic exercise may be a useful interest strategy if your goals are to improve recovery of voluntary force, lactate clearance, or the total number of subsequent repetitions. The exercise intensity needs to be low and the target region needs to differ from the region being trained.
Overall, the inclusion of aerobic exercise seems promising to improve the recovery of voluntary force, lactate clearance, and the total number of performed repetitions if the selected intensity is low enough to avoid lactate accumulation (e.g., stationary bike between upper body sets). If aerobic exercise enhances fatigue and reduces the volume of resistance training, you are better off eliminating it as an interesting strategy.
Interset foam rolling is a strategy you likely want to avoid. While it may feel good, the limited evidence we have suggests it may impair force production, fatigue resistance, and repetition performance when used on the agonist and antagonist muscles of the legs. The 3 studies used 60 and 120-second durations, so perhaps a lower amount won’t have a negative effect (pure speculation). Massage has even less evidence and shows no performance improvements. Whole-body vibration may have small benefits, but it’s not feasible. The cost and space requirements are not worth the minimal effects.
HR-based rest periods may be an effective way to personalize training. The premise is to rest until your body reaches a target heart rate, which signals you are sufficiently recovered for your next bout of exercise. Like RPE and RIR for resistance training, HR-based rest periods support autoregulation, accounting for the daily fluctuations in performance potential. The target heart rate will depend on the targeted energy system, training history, age, and health status of the individual.
So, what strategies should be prioritized in the clinic and gym? Based on this work and other work on training volume and intensities, you should still focus on the primary variables: volume and intensity. The total rest duration is likely more important than what you do during the rest. Perhaps you can squeeze out a few extra reps if you implement cooling or stretching but the effect sizes are small. I recommend ensuring your volume and intensity are correct and you have an autoregulation approach that ensures your work-to-rest ratio is appropriate first. If you have the fundamentals down, you can experiment with interest strategies.