30-Second and 3-Minute Rest Intervals Did Not Lower Next-Day Triglycerides in Lifters

Rest intervals changed how long a lifting session took and how much energy it used, but not the blood fat response researchers were tracking. In a randomized crossover trial, 25-minute and 75-minute versions of the same workout left next-day triglycerides after a fat-containing meal without a significant difference.

Rest intervals are one of the easiest training variables to adjust. Cut the rest between sets and the same work fits into a fraction of the time. A study published September 14 in the European Journal of Clinical Nutrition asked whether that choice also changes a cardiovascular risk marker the next morning: the rise in blood triglycerides after eating.

Fifteen healthy, resistance-trained young men completed three trials in random order, each separated by a seven-day washout. In one, they rested 30 seconds between sets. In another, they rested 180 seconds. In the control trial, they rested throughout the day. Both lifting sessions used identical exercises, sets, repetitions and external loads.

The answer was clear for the main outcome. Participants lifted a total of 6,433 kilograms on average in each exercise trial, yet fasting and postprandial triglyceride concentrations did not differ significantly among the short-rest, long-rest and control trials.

How the Rest Intervals Trial Worked

The sessions were built to isolate one variable. Participants performed three sets of 8 to 12 repetitions across seven whole-body exercises: barbell squats, dumbbell lateral raises, barbell bench press, dumbbell twisting biceps curls, barbell Romanian deadlifts, dumbbell lying triceps extensions and bent-over rows.

Loads were set at 70% of each participant’s 8-repetition maximum for compound lifts and 80% of the 12-repetition maximum for isolation exercises. Only the rest changed. With 30 seconds between sets and exercises, the full session took 25 minutes. With 180 seconds, it took 75 minutes.

The test came the following morning. About 17.25 hours after exercise, participants ate a standardized breakfast scaled to body mass, providing 0.56 grams of fat per kilogram. Blood samples were taken before the meal and at 0.5, 1, 1.5, 2, 4 and 6 hours afterward.

No Significant Difference in Triglycerides

Triglycerides are the most common type of fat in the body, and elevated levels after meals are considered a cardiovascular risk factor. Earlier research has shown that single bouts of resistance exercise can reduce the postprandial rise in triglycerides, even though lifting typically burns less energy than aerobic exercise.

This trial did not reproduce that effect. The researchers found no significant differences in fasting triglycerides, with a P value of 0.061, or in the postprandial response, with a main trial effect P value of 0.147 and a trial-by-time interaction P value of 0.058. Total and incremental area-under-the-curve values also did not differ among trials.

Two of those P values sit close to the conventional 0.05 threshold. With only 15 participants, the study cannot rule out a small effect that a larger trial might detect. But on the evidence reported, changing rest intervals did not produce a meaningful triglyceride advantage in this group.

The Long-Rest Session Used More Energy

Longer rest did change several secondary measures. Gross energy expenditure during the long-rest session was 1.10 megajoules, about 263 kilocalories, compared with 0.63 megajoules, about 151 kilocalories, for the short-rest session. Part of that gap reflects the extra 50 minutes spent in the gym.

Net energy expenditure, which accounts for resting metabolism, was also higher with long rest: 0.61 megajoules versus 0.49 megajoules, or roughly 146 versus 117 kilocalories. Even so, the authors note that this difference did not translate into different postprandial triglycerides.

Fasting insulin was lower after the long-rest trial than after the control trial, and HOMA-IR, an estimate of insulin resistance, was lower after long rest than after short rest. The authors suggest the higher net energy expenditure may help explain those differences. Blood lactate, by contrast, was significantly higher in the short-rest session, reflecting its denser format with far less recovery between sets.

Why the Result May Differ From Earlier Studies

The authors offer two main explanations. First, the participants were metabolically healthy, resistance-trained young men with low baseline triglycerides. People who already clear dietary fat efficiently may have less room for a single workout to improve the response.

Second, the protocol sat at the lower end of set volume and at mid-to-lower intensity compared with earlier studies that reported triglyceride reductions after resistance exercise. A higher-volume or heavier session might produce a different result.

What Earlier Rest Intervals Research Found About Muscle Growth

The new trial looked only at blood fats, but rest intervals have been studied far more often for muscle growth. That literature helps explain why the timer between sets remains a live debate among coaches.

A 2024 systematic review with Bayesian meta-analysis in Frontiers in Sports and Active Living pooled nine studies on inter-set rest and hypertrophy. The authors reported a small hypertrophic benefit for resting longer than 60 seconds between sets, possibly because very short rest reduces the load lifted across a workout.

The same review found no appreciable differences in hypertrophy when rest extended beyond 90 seconds, and the estimates for different rest periods overlapped substantially. In other words, very short rest may cost a little growth if it forces lighter loads or fewer repetitions, while longer rest beyond about a minute and a half appeared to add little on average.

The European Journal of Clinical Nutrition trial deliberately removed that trade-off by holding the load, sets and repetitions constant. That makes its metabolic comparison cleaner, but it also means real-world lifters who shorten rest intervals may end up lifting less than the participants did.

What Lifters Can Take From the Rest Intervals Data

The study does not tell anyone how long to rest for strength or muscle growth. The load was fixed by design, so it could not show whether longer rest intervals would have allowed heavier weights or more repetitions, which is a common reason coaches prescribe them for heavy compound lifts.

What it does suggest is narrower and still useful. For healthy, trained young men, choosing shorter or longer rest between sets does not appear to be a decisive lever for next-day blood fat after a single session. Rest can reasonably be chosen for other goals, such as training quality, session length and how demanding the workout should feel.

• When time is tight, short rest intervals can fit the same volume into far less time, though the session becomes much harder.
• When performance on heavy sets matters, longer rest remains a sensible default.
• For metabolic health, consistency across weeks of training and total daily movement likely matter more than the timer between sets.

Rest is one of several variables worth understanding. Our reports on partial range of motion training and estimating deadlift 1RM from bar speed examine other levers that change how a session feels and performs.

Recovery after the last set matters too. Fitness Living recently covered research on static stretching after lifting and vascular recovery. And for the bigger picture on intensity outside the weight room, see today’s report on vigorous activity and mortality in 147,414 adults.