Between 40 and 75 minutes for most people, warm-up included. That figure is an output, not a target: it follows from your number of working sets multiplied by what each one costs in time. Sessions consistently past 90 minutes mean your volume is badly distributed.
An hour, says the internet. That figure rests on nothing in particular, except that an hour is a round number and gyms like to sell hour-long slots.
Session length is not something you decide. It is something you derive — from how many sets you have to do, how long you rest between them, and how long each set takes.
Where session length actually comes from
The arithmetic, in three lines
A set of 8 to 12 reps takes 30 to 45 seconds. Rest runs 2 to 3 minutes on heavy compounds, 60 to 90 seconds on isolation work.
Add them up: each set costs between 1 min 30 and 3 min 30 depending on the exercise. Multiply by your working sets, add 8 to 12 minutes of warm-up, and you have your duration.
- 12 sets → roughly 35 to 45 minutes
- 18 sets → roughly 50 to 60 minutes
- 25 sets → roughly 70 to 85 minutes
If your sessions consistently run past 90 minutes, it is almost never a pacing problem. It is that your volume is too high for the number of sessions you do.
Why going longer does not help
The "cortisol spikes after 45 minutes" claim has no basis. Your body does not begin dismantling muscle because a clock passed a number.
The real problem is different and genuine: the quality of your final sets collapses. After an hour of hard work, concentration drops, technique degrades, and end-of-session sets contribute mostly fatigue. You pay the recovery cost without collecting the benefit.
When sessions stretch, the fix is not to rush the rest periods — that sacrifices the performance of your heavy sets. It is to cut an accessory exercise, or spread the volume over one more session.
Rest is not wasted time
This is the most common mistake among people trying to compress a session.
On heavy lifts, rest is what allows the next set to be as productive as the last. Dropping from three minutes to one between squat sets does not make the session more efficient — it makes it more tiring and less productive. You complete fewer reps at the same load, which is less useful volume, not more.
Where you can genuinely save time without losing anything: alternating sets between opposing muscle groups. While your back recovers, your chest works. Rest per muscle stays complete; total session time drops considerably.
Training short, when life demands it
A well-built 30-minute session beats a one-hour session that does not happen. The rule is simple: keep the compounds, cut the accessories.
One squat pattern, one press, one pull — three exercises, three or four sets each, and you have covered the essentials in half an hour. What goes first is lateral raises and curls, not the movements that shift the most load.
Across several weeks, four 40-minute sessions beat two 80-minute ones: identical weekly volume, double the frequency — and frequency is what makes the difference.
Does the warm-up count?
Yes, and it does not get cut. Eight to twelve minutes covers it: a few minutes of general movement, then progressive load ramps on your first heavy exercise — 40%, 60%, 80% of your working weight.
Those ramp-up sets do not count toward your volume. They are not taken near failure and produce no growth stimulus; they prepare your nervous system and joints. Counting them would badly distort your volume arithmetic.
Related
- Volume calculator — the variable that actually sets your session length.
- Rest between sets — the second half of the calculation.
- Training four days a week — spreading volume to shorten sessions.
- How many reps per set — what happens inside each set.
Frequently asked questions
How long should a workout be?
Between 40 and 75 minutes for most people, warm-up included. But duration is not a target: it follows from your number of sets and your rest periods. Twelve working sets gives roughly 40 minutes; eighteen gives about an hour.
Is a workout over an hour counterproductive?
Not for hormonal reasons — the idea of a cortisol threshold at 45 minutes has no basis. The real issue is that the quality of your final sets collapses: after an hour of hard work, technique degrades and the ratio of accumulated fatigue to useful stimulus worsens.
Can you make progress with 30 minute workouts?
Yes, provided you keep the compound lifts and cut the accessories. One squat pattern, one press and one pull cover the essentials. Four 40-minute sessions beat two 80-minute ones: same weekly volume, double the frequency.
Should I cut rest periods to shorten my workout?
No — it is the worst way to save time. On heavy lifts, shortened rest reduces the reps you complete at a given load, which is less useful volume. Cut an accessory exercise instead, or alternate sets between opposing muscle groups.
Does the warm-up count toward workout duration?
Yes, and you should plan for 8 to 12 minutes. However, warm-up and ramp-up sets do not count toward training volume, because they are not taken near failure and produce no growth stimulus.