What the research actually shows

The short-rest prescription, 30 to 60 seconds between sets for hypertrophy, keep the heart rate up, stay in the burn, was once standard advice. It has been substantially challenged by more recent evidence.

For strength development the case is clear. A systematic review of 23 studies found that rest intervals greater than 2 minutes are required to maximize strength gains in trained individuals (Grgic et al., 2018). A 2024 study in the Journal of Strength and Conditioning Research found that 5-minute rest intervals preserved peak force output with only a 4% reduction compared to 17% with 2-minute rest. That is not a marginal difference. That is a fundamentally different training stimulus.

For muscle growth, the picture is more nuanced but points in the same direction. Longo et al. (2022) demonstrated that when total training volume was equalized, rest interval length had no independent effect on hypertrophy. The real driver of muscle growth is total volume load, and shorter rest periods reduce the volume you can sustain, which reduces your results. The 2026 ACSM Position Stand now classifies the evidence for short rest and hypertrophy as insufficient to draw definitive conclusions.

The most striking finding came from McKendry et al. (2016), who directly measured muscle protein synthesis after training. Five-minute rest produced a 152% increase in MPS in the four hours following exercise. One-minute rest produced 76% — from the same workout. The short-rest group had higher testosterone and lactate responses — the very hormonal signals that gave short rest its reputation. But the intracellular machinery that actually builds muscle responded more strongly with longer rest.

The burn does not equal the build.

Why this matters more after 40

Phosphocreatine is the energy substrate your muscles depend on for high-intensity work. It recovers more slowly with age. A 2025 meta-analysis confirmed that greater age is significantly associated with longer phosphocreatine recovery times in working muscles. Older adults also accumulate inorganic phosphate approximately 1.8 times faster during exercise — a metabolite that directly impairs force production between sets.

In practical terms: the rest your muscles needed at 30 is not the rest they need now. This is physiology, not weakness. Programming around it is not a concession — it is smart training.

The 2026 ACSM Position Stand also notes that lifting to muscular failure may be inadvisable for older adults due to cardiovascular risk and increased injury likelihood from form breakdown under fatigue. Adequate rest between sets directly supports movement quality and training safety.

A practical framework

The ACSM notes that rest period length should vary by the primary objective of each exercise — not a single uniform number applied across an entire session. For adults over 40, a useful starting framework:

→ Heavy strength sets (≥80% 1RM): 3–5 minutes
→ Hypertrophy accessory work (60–80% 1RM): 2–3 minutes
→ Muscular endurance work (<50% 1RM): 30–90 seconds
→ Adults 40+ across all categories: err toward the longer end of each range

Auto-regulated rest, resting until you are genuinely ready rather than adhering to a fixed interval, is also well-supported by the evidence, particularly for older adults whose recovery capacity varies more between sessions and individuals.

Structure your session with heavy compound lifts first using longer rest, then move to accessory work with moderate rest. Use a timer. Not a feeling.

The bottom line

Longer rest between sets is not a sign that you are training less seriously. For adults over 40 with goals around strength and muscle preservation, adequate rest may be one of the highest-leverage adjustments available and one of the most consistently underused.

The long game requires training smarter than you did at 30. This is one of the ways to do that.

Richard Skolasky is an ACE Certified Personal Trainer. This article is for general educational purposes only and does not constitute individualized exercise prescription. Consult a qualified healthcare provider before beginning or modifying a training program.

REFERENCES

Grgic et al. (2018). Effects of rest interval duration on strength. Sports Medicine, 48(1), 137–151.

McMahon et al. (2024). 5-min vs 2-min rest intervals, force output. Journal of Strength and Conditioning Research, 38(9), 1527–1534.

Longo et al. (2022). Volume load vs rest interval and hypertrophy. JSCR, 36(6), 1554–1559.

McKendry et al. (2016). Short rest blunts myofibrillar protein synthesis. Experimental Physiology, 101(7), 866–82.

Currier et al. (2026). ACSM Position Stand — resistance training prescription. Med Sci Sports Exerc, 58(4), 851–872.

Singh et al. (2025). PCr recovery kinetics — age-related differences. NMR in Biomedicine, 38(5).