Lab Report #1: The Truth about Mass
The Lab Report is our new monthly research letter: one topic, the best current science, translated into what to actually do in the gym. Issue #1 is about the most important physical asset you own — your muscle.
THE NUMBERS NOBODY TELLS YOU ABOUT TURNING 40
From midlife on, your muscle quietly shrinks — roughly half a percent a year at first, accelerating to around 1% a year by your seventies. By then, most people are walking around with about 80% of the muscle they had in their twenties. And here's the part that should get your attention: strength drains two to five times faster than size, falling as much as 3–4% a year by your mid-seventies. In the research, it's that loss of strength — more than the loss of muscle itself — that tracks with disability and early death.
Muscle is what gets you up off the floor, catches you when you trip, and keeps you carrying your own groceries, your own luggage, your own life. Think of it as a retirement account: every hard set is a deposit; every year you don't train, aging makes a withdrawal. You can't stop the withdrawals — but you can absolutely out-deposit them.
The good news: muscle stays trainable at every age. And this year, the science on exactly how to build it got its biggest update in nearly two decades — the American College of Sports Medicine's 2026 Position Stand, their first full update since 2009, built on 137 systematic reviews and more than 30,000 study participants, plus the newest dose-response research on training volume. One honest caveat: most of this research was done on younger lifters. The principles, though, are the same ones we coach at every age.
THE PROTOCOL: WHAT THE SCIENCE ACTUALLY SAYS
1. Do enough sets — about 10 to 20 per muscle, per week. The newest analysis of 67 studies found growth keeps rising with weekly sets, with the sweet spot around 10–20 hard sets per muscle group. Work a muscle indirectly — triceps during pressing, for example — and it counts as about half a set.
2. Train hard — but you don't have to fail. Stop most sets 1 to 3 reps short of failure. Grinding every set to the absolute limit adds fatigue, not muscle — for strength, skipping failure may actually be better.
3. The weight matters less than the effort. From about 30% to 100% of your max, muscles grow the same when the effort is matched. In practice: most work lands between 5 and 20 reps. Pick loads your joints like.
4. Twice a week per muscle — for logistics, not magic. At equal weekly volume, frequency itself adds nothing. Twice a week wins because 10–20 quality sets don't fit in one session: early analysis puts the useful ceiling near 11 sets per muscle per workout.
5. Rest longer than feels natural. More than 60 seconds between sets — 90 seconds to 3 minutes on big lifts. The old 30-second “feel the burn” rest turns out to cost you reps, not buy you growth.
6. Train the stretch. Full range of motion, and favor exercises that load the muscle in its lengthened position — deep split squats, seated curls, overhead extensions. That stretched-position work is where a real share of the growth signal lives.
WHAT THE SCIENCE RETIRED
A few old rules didn't survive the update. The famous “8–12 rep hypertrophy zone”? Anywhere from 5 to 30 reps works. Slow-motion reps and time-under-tension targets? No benefit. Fancy techniques like drop sets and supersets? They don't grow more muscle — they just make the workout shorter, which is still a fine reason to use them. The pattern across all of it: muscle-building is simpler than the industry sells. Enough hard sets, close to your limit, full range of motion, week after week. The basics were the secret all along.
COME TRY IT IN THE GYM
Reading about hard sets is one thing — feeling one is another. So here's the invitation: grab a free 3-day trial pass, come in, and run this exact protocol — two sessions, one muscle group, 10-plus hard sets, a rep or two in the tank. We'll be on the floor to coach it, and you'll leave knowing exactly what a properly hard week of training feels like.
— Navin, Refinery Fitness, Rhinebeck NY
SOURCES
Mitchell WK et al. Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength: a quantitative review. Frontiers in Physiology, 2012. Read the paper
Currier BS et al. American College of Sports Medicine Position Stand on resistance training prescription. Medicine & Science in Sports & Exercise, 2026. Read the paper
Pelland JC et al. Meta-regressions of weekly resistance training volume and frequency. Sports Medicine, 2026. Read the paper
Robinson ZP et al. Dose–response relationship between proximity to failure, strength gain, and muscle hypertrophy. Sports Medicine, 2024. Read the paper
Lopez P et al. Resistance training load effects on muscle hypertrophy and strength gain: systematic review and network meta-analysis. Medicine & Science in Sports & Exercise, 2021. Read the paper
Wolf M et al. Lengthened partial repetitions vs. full range of motion in trained individuals. PeerJ, 2025. Read the paper
