“I never miss one of my five weekly sessions”: the point in the week where the extra hours stop giving lifters anything back

Five gym sessions a week sounds impressively disciplined. But the numbers coming out of exercise science labs tell a less flattering story: for most lifters, the returns on that fifth workout are far smaller than the ones banked earlier in the week, and sometimes they’re not there at all.

A 2025 meta-regression published in Sports Medicine, pooling data across dozens of resistance training studies, looked directly at what happens as weekly frequency climbs. As frequency increases, results indicate there is a negligible effect for muscle hypertrophy but a meaningful effect with diminishing returns for strength gains. In plain terms: training a muscle more often barely moves the needle on size once you’ve covered the basics, and even for pure strength, each additional session buys you progressively less than the one before it.

Where the curve actually bends

The bend in that curve tends to show up around session three or four for most trained lifters, not session five. Research analysing per-session training volume, drawing on data from over 2,000 participants across 67 studies, found something strikingly specific: meaningful strength gains plateau after just two focused sets per session, while muscle growth peaks around eleven sets. Push far beyond that within a single workout, and the findings challenge the “more is always better” mentality that dominates many training programs, suggesting strategic, shorter workouts can deliver comparable results to marathon gym sessions.

That’s the trap with a rigid five-day habit. If your weekly set total for a given muscle group was already sufficient by day three, days four and five aren’t adding stimulus, they’re adding fatigue. Older frequency research illustrates this well. A frequently cited study on untrained men examined strength gains when performing bench press lifts at either 1, 2, 3, 4, or 5 days a week for 8 weeks, and training 5 days a week produced greater strength improvements than the other groups. The catch, and it’s an important one, is that the total weekly volume between groups was not equalised, with higher weekly frequency groups performing significantly more overall work. So the fifth session only “won” because it came with more total lifting attached, not because five sessions is magically superior to three.

It’s the sets, not the days on the calendar

This is where most lifters misread the research. Frequency itself isn’t the lever that builds muscle or strength, weekly volume is, and frequency is just one way of parcelling that volume out. Splitting the same training volume into more frequent training sessions is superior for hypertrophy, likely because the muscle-building stimulus is distributed more optimally over the course of the week. That’s a genuine advantage of training five days rather than two, but it only holds if you’re spreading a fixed amount of work more thinly, not stacking additional work on top.

Guidance from sports science bodies has historically undersold how thin the evidence base is here. Physical activity guidelines from organisations including the American College of Sports Medicine recommend a frequency of 2 to 3 days a week for healthy adults, though these recommendations are notional, derived from conjecture rather than robust scientific evidence. Where the data is more consistent is on volume ceilings: the sweet spot for most people sits somewhere between 10 and 20 sets per muscle group per week, and going above 20 sets a week does not produce meaningfully more muscle growth and in some cases may hinder it. Once you’ve hit that ceiling, a fifth session targeting the same muscles isn’t a bonus, it’s overflow.

There’s a second, less obvious mechanism at play within each session too. Cramming too many sets into one sitting degrades the quality of the later ones through accumulated fatigue, which is precisely why splitting volume across the week can outperform two exhausting sessions. Very high single-session volumes hit diminishing returns within the session because the last few sets contribute less due to accumulated fatigue, and splitting the volume across two sessions keeps every set closer to peak quality. A fifth weekly session only earns its place in your programme if it’s doing this job, redistributing quality work, rather than simply extending an already-sufficient week.

What this means for your week

None of this is an argument against training five times a week. Plenty of well-trained lifters do exactly that, particularly when they’re deliberately keeping each session shorter and using the extra day to target lagging muscles or allow more recovery between hard efforts on any one area. The problem is treating the fifth session as automatically additive, when the honest answer from the data is “it depends on what you’re already doing on days one through four.”

A useful check is simply to total up your weekly sets per muscle group before adding another day to the calendar. If you’re comfortably inside the 10-to-20-set range spread across three or four sessions, session five is likely there for adherence, mental rhythm, or targeting a weak point, not raw growth. If you’re someone who genuinely needs the extra recovery time between heavy compound lifts, spreading familiar volume more thinly across five shorter sessions can be a smart trade rather than an unnecessary one. Either way, the number worth tracking isn’t how many days you showed up. It’s whether the eleventh set for that muscle this week did anything the tenth hadn’t already done. As always, if you’re managing an injury, a health condition, or simply unsure how hard to push your training schedule, it’s worth checking with your GP or a qualified physiotherapist before making major changes.

Sources : pubmed.ncbi.nlm.nih.gov | sportrxiv.org