By Emmett Shaul
BLUF
A Journal of Strength and Conditioning Research study compared 2-minute vs 5-minute rest intervals between sets during heavy isometric knee extension in 8 young, recreationally active adults.
With the same exercise, sets, and reps in both conditions:
- Strength across sets – With 5-minute rest, peak force stayed stable across all 4 sets. With 2-minute rest, strength clearly dropped in sets 3 and 4.
- Total work – The 5-minute condition produced about 15% more total work (≈11,200 vs 9,700 N·m of torque).
- Fatigue – After the session, maximal strength dropped by about 17% with 2-minute rest, but only about 4% with 5-minute rest. Muscle activation showed a similar pattern.
- Metabolic stress – Blood lactate was higher overall in the 2-minute rest condition.
- How it felt – Heart rate and rating of perceived exertion increased over the session in both conditions and were similar between rest intervals.
In this lab setting, 5-minute rest intervals produced more and better-quality work with less neuromuscular fatigue, even though the sessions felt just as hard as 2-minute rest.
Context
Skeletal muscle mass is heavily influenced by mechanical loading – how much force a muscle produces and how much total work it performs. There is a clear relationship between training volume and hypertrophy, and one simple way to influence volume is to change rest between sets.
Most traditional recommendations for hypertrophy in young adults use 1–2 minutes of rest for novice and intermediate lifters and 2–3 minutes for advanced lifters. At the same time, several studies have shown that longer rest intervals (4–5 minutes) allow lifters to complete more total work than 2–3 minute rests when load and sets/reps are matched.
This study directly compared 2-minute and 5-minute rest intervals and measured how they affect force, muscle activation, blood lactate, heart rate, and perceived effort within a single heavy session.
Study Overview
Eight healthy, recreationally active adults (7 men, 1 woman; average age about 22 years) took part. All were physically active but had not been in a formal lower-body resistance training program for at least 6 months.
The study used a within-subject, randomized, crossover design. Each subject completed:
- One familiarization session (1 set of 8 maximal efforts), and
- Two experimental sessions, separated by 4 days, with identical exercise protocols but different rest intervals:
- REST-2: 2-minute rest between sets
- REST-5: 5-minute rest between sets
The exercise in both experimental sessions was unilateral isometric knee extension on an isokinetic dynamometer:
- Knee fixed at 90° flexion
- 4 sets of 8 repetitions
- Each rep: 3-second maximal voluntary isometric contraction
- 2 seconds passive rest between reps within a set
In each condition, every subject completed 32 maximal contractions.
Before each session (5 minutes pre-exercise) and after each session (5 minutes post-exercise), the researchers measured:
- Maximal peak torque (knee extension strength)
- Surface EMG amplitude of the quadriceps (vastus lateralis)
During the session they recorded:
- Peak torque (PT) and mean torque (MT) for each set
- EMG amplitude and frequency measures
At rest, immediately after each set, and near the end of each rest period, they measured:
- Blood lactate
- Heart rate
Rating of perceived exertion (RPE) was recorded after each set.
Total exercise volume for each condition was defined as the sum of mean torque across all 32 contractions.
Results
Strength during the session
With 2-minute rest:
- Peak torque was lower in sets 3 and 4 than in set 1, and set 4 was also lower than set 3. Strength clearly tailed off in the second half of the session.
With 5-minute rest:
- Peak torque did not differ between sets. Strength was maintained across all 4 sets.
Across the workout, peak torque was lower overall in the 2-minute condition than in the 5-minute condition.
Change in maximal strength
Comparing pre- and post-session maximal tests:
- In the 2-minute rest condition, maximal knee extension strength decreased by about 17%.
- In the 5-minute rest condition, it decreased by about 4%.
So, subjects finished the session much more fatigued when they only had 2 minutes of rest between sets.
Mean torque and total work
Mean torque showed a similar pattern:
- With 2-minute rest, mean torque declined in every successive set after set 1.
- With 5-minute rest, mean torque only dropped notably in set 4; sets 1–3 were better preserved.
- In sets 2, 3, and 4, mean torque was higher with 5-minute rest than with 2-minute rest.
When all mean torque from the 32 contractions was summed:
- 2-minute rest produced about 9,748 N·m of torque.
- 5-minute rest produced about 11,212 N·m of torque.
This is roughly 1,500 N·m more work, or about 15% greater total exercise volume, in favor of the 5-minute rest condition.
Neuromuscular activity (EMG)
EMG amplitude during the sets showed that:
- With 2-minute rest, EMG in set 4 was lower than in set 1, indicating reduced muscle activation as fatigue accumulated.
- With 5-minute rest, EMG amplitude did not change across sets.
Overall, EMG amplitude across the workout was lower in the 2-minute condition than in the 5-minute condition.
Pre- to post-session changes in EMG during maximal tests matched the torque results:
- EMG amplitude dropped by about 29% in the 2-minute rest condition.
- It dropped by about 10% in the 5-minute rest condition.
So, muscle activation fell almost three times more with 2-minute rest than with 5-minute rest. EMG frequency measures changed only slightly with set number and did not differ meaningfully between rest conditions.
Metabolic stress and effort
Blood lactate:
- Increased over sets in both conditions.
- There was an interaction showing higher lactate overall in the 2-minute rest condition across the session, although direct comparisons at the same time points did not reach significance.
Heart rate:
- Increased during and after sets compared to rest in both conditions.
- The abstract reports no main effect of condition on heart rate, indicating similar average heart rate responses across the session in both rest conditions.
RPE:
- Increased from set 1 (~16) to sets 2–4 (~18–19) in both conditions.
- There was no effect of rest duration on RPE and no interaction between set and rest.
In practical terms, both protocols felt equally hard, even though 5-minute rest allowed higher forces, higher activation, and more total work.
Takeaways
- Five-minute rest preserved strength across sets, while two-minute rest led to clear strength drop-offs in the final sets.
- Total work was higher with 5-minute rest, by about 15%, even though the sets and reps were identical.
- Neuromuscular fatigue was lower with 5-minute rest. Maximal strength and EMG dropped much more after the session when only 2 minutes of rest were used.
- Metabolic stress was higher with 2-minute rest, as shown by higher blood lactate across the session, but this came with less high-quality work, not more.
- Heart rate and perceived effort were similar between conditions. Both sessions felt very demanding.
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