The New ACSM Resistance Training Guidelines: What Changed, Why It Matters, and How We Use Them at Defiance
The New ACSM Resistance Training Guidelines: What Changed, Why It Matters, and How We Use Them at Defiance
The American College of Sports Medicine just published its first major update to resistance training guidelines since 2009. That's a 17-year gap. Every doctor, PA, NP, physical therapist, and personal trainer currently in practice was trained on guidance that predates GLP-1 medications, modern hormone therapy protocols, and most of what we now know about how aging adults respond to strength work.
The new position stand synthesizes 137 systematic reviews and more than 30,000 participants. That makes it one of the highest-evidence documents in exercise medicine, full stop. And while it's labeled as guidance for "healthy adults," the implications for the patients we see every day — women on hormone therapy, patients on medical weight loss programs, Emsculpt NEO patients building lean muscle — are direct and significant.
This guide walks through what actually changed in the new guidelines, what didn't change (which is just as important), and how we're integrating this into how we coach patients at our Centennial clinic in the Denver Tech Center. Our patients come from across the south Denver metro — Castle Rock, Castle Pines, Lone Tree, Greenwood Village, Highlands Ranch, Parker, Cherry Hills Village, and Englewood — and most of them are trying to figure out how to combine medical care with the active lifestyle that defines living in Colorado.
If you're on hormone therapy, on a medical weight loss program, considering Emsculpt NEO, or just trying to age well, the new guidance matters. Here's the honest clinical read.
- The new ACSM position stand synthesizes 137 systematic reviews and over 30,000 participants — one of the most evidence-rich documents in exercise medicine.
- Resistance training significantly improves strength, muscle size, power, endurance, gait speed, balance, and overall physical function.
- For strength: lift heavier loads (≥80% of your one-rep max), full range of motion, 2-3 sets, at the beginning of sessions, twice a week minimum.
- For muscle size (hypertrophy): higher volume (≥10 sets per week per muscle group) and eccentric overload.
- Many popular "principles" — training to failure, equipment type, fancy periodization, blood flow restriction — did NOT consistently impact outcomes.
Why a 17-Year Gap Matters
The previous ACSM resistance training position stand was published in 2009. That document still shapes how most fitness professionals, primary care providers, and even physical therapists think about strength work. A lot has changed since.
In 2009, we didn't yet have widespread use of GLP-1 medications for weight loss. We didn't have widespread acceptance of testosterone optimization in women. We didn't have devices like Emsculpt NEO that supplement (not replace) strength training. We didn't have the depth of research on aging muscle that's emerged in the last decade. We didn't have the awareness of sarcopenia — age-related muscle loss — as a clinically significant condition.
What that means practically: if your primary care doctor or trainer is giving you guidance that sounds like "lift light weights for high reps to tone" or "cardio first, then strength," they're using an outdated mental model. The new evidence is clear and the recommendations are different.
What the New Guidelines Actually Say
The ACSM position stand evaluated which specific resistance training variables produced which specific outcomes. The findings are unusually clear for an exercise research document — most variables we obsess over don't matter as much as we think, and a few simple principles drive most of the results.
For building strength
Strength is enhanced by:
- Heavier loads — at least 80% of your one-rep max
- Full range of motion — not partial reps
- 2-3 sets per exercise
- Done at the beginning of training sessions, when you're fresh
- Minimum 2 sessions per week
Practical interpretation: most patients we see who say "I lift weights" are doing something different from what builds actual strength. They're doing higher rep ranges (12-15+) with lighter loads. That builds endurance and some hypertrophy, but it doesn't optimally build strength. If your goal is to be stronger — and for most adults over 40, it should be — the work needs to be heavier and more intentional.
For building muscle (hypertrophy)
Muscle size is enhanced by:
- Higher weekly volume — at least 10 sets per week per muscle group
- Eccentric overload — emphasizing the lowering phase of each lift
Practical interpretation: building muscle requires more volume than most people are doing. Two squat workouts a week of 3 sets each (6 total sets) likely won't drive significant hypertrophy. Getting to 10+ sets per muscle group per week takes intentional programming. This matters enormously for our weight loss patients — preserving muscle during weight loss is the whole game, and you can't preserve what you didn't build adequately in the first place.
For building power
Power (which is strength × speed, and matters more than people realize for daily function and injury prevention) is enhanced by:
- Moderate loads — 30-70% of one-rep max
- Lower volume — fewer total reps
- Olympic-style weightlifting or power-focused movements
- Fast concentric phase — moving the weight with intent
Practical interpretation: this is one of the most under-trained qualities in adults over 40. Power declines faster than pure strength with age, and it's the quality most associated with reduced falls, faster reaction times, and overall physical function in later decades. You don't need to be doing Olympic lifts to train power — even fast-paced bodyweight movements with intent can help.
What Doesn't Matter As Much As You've Been Told
This is the section that should change how a lot of people approach training. According to the new guidelines, the following variables did NOT consistently impact outcomes across the 137 systematic reviews:
- Training to muscular failure — you don't need to push every set to "I can't do another rep"
- Equipment type — barbell vs. dumbbell vs. machine vs. bands, the body adapts to load regardless
- Exercise complexity — fancy movements don't outperform basic compound lifts
- Set structure — drop sets, supersets, rest-pause, all comparable to straight sets when total volume is matched
- Time under tension — slow eccentric tempos, fast tempos — outcomes are similar
- Blood flow restriction — not consistently better than standard training
- Periodization scheme — linear vs. undulating vs. block, when applied appropriately, comparable results
The takeaway isn't that these variables are useless — they each have specific applications. The takeaway is that the obsessive focus on training minutiae often comes at the expense of what actually drives results: consistent, progressive, intentional training at appropriate loads, 2+ times per week, for years.
Why This Matters Specifically for Defiance Patients
The new guidelines have direct implications for three of the patient populations we work with most often. Here's how we're applying them.
For hormone therapy patients
For women on bioidentical hormone therapy and men on testosterone optimization, resistance training is not optional. The two most important reasons:
First, lean muscle is the largest reservoir of metabolic activity in the body. Hormone optimization works best when there's adequate muscle for hormones to act on. Patients with low muscle mass get suboptimal results from hormone therapy because the system being optimized is depleted.
Second, the new guidelines confirm that heavier loads drive strength, and strength drives the body composition changes most patients are looking for. Light-weight, high-rep "toning" workouts produce minimal changes in body composition regardless of hormone status. The combination of hormone optimization plus appropriately heavy resistance training is dramatically more effective than either alone.
For our patients in the south Denver metro area, that often means working on local recommendations for gyms or trainers familiar with this style of training. We're happy to point patients toward providers in the DTC, Greenwood Village, or surrounding areas who actually train this way rather than offering watered-down generic fitness programming.
For GLP-1 and medical weight loss patients
This is the population for whom the new guidelines might matter most. The biggest clinical concern with GLP-1 weight loss medications — semaglutide, tirzepatide, and others — is loss of lean muscle mass alongside fat loss. Studies show that without intervention, roughly 25-40% of weight lost on these medications can be lean tissue. That's a problem clinically and aesthetically.
The new ACSM guidelines essentially give us the protocol: heavy loads, 2-3 sets, 2+ sessions per week minimum, eccentric overload. Patients who follow this while on GLP-1 medications preserve muscle dramatically better than patients who don't.
Our medical weight loss program includes specific coaching on training volume and intensity for exactly this reason. Patients who treat their GLP-1 protocol as "I just need to eat less and the medication will work" lose muscle they can't easily rebuild. Patients who pair the medication with the right resistance training keep what matters and lose what doesn't.
If you're on a GLP-1 medication and not doing intentional resistance training, you're not getting the best outcome the medication can produce. This is the single most consistent gap we see in patients who come to us mid-protocol from other providers — the medication is working on appetite, but no one has talked with them about preserving muscle.
For Emsculpt NEO patients
Emsculpt NEO works by inducing supramaximal muscle contractions — 20,000 per 30-minute session — that are not achievable through voluntary training. This produces measurable changes in muscle mass and fat in the treated area.
But Emsculpt NEO is not a substitute for resistance training. It's most effective in patients who are also strength training, because the underlying muscle quality, neural patterning, and metabolic environment determine how well the body responds to the supramaximal contractions. Patients who treat Emsculpt NEO as "a workout you don't have to do" leave significant results on the table.
The new ACSM guidelines give us a clear framework for what to recommend alongside Emsculpt NEO: 2-3 sessions per week of progressive strength work, focused on the muscle groups complementary to what Emsculpt is treating. We don't expect patients to become competitive lifters — we expect them to take the medication of resistance training as seriously as any other part of their care plan.
The Colorado-Specific Angle
One thing about training in Colorado that's worth naming: altitude affects training response in ways that aren't always discussed. The reduced oxygen at higher elevations (the south Denver metro sits at roughly 5,400 feet) affects cardiovascular adaptations more than strength adaptations, but it does compound recovery demands.
Practical implication: Colorado patients often need slightly more recovery between heavy sessions than their counterparts at sea level, especially during the initial weeks of a new training program. This is one of those small details that gets missed by generic online training programs but shows up in patient outcomes when you've worked with hundreds of Colorado patients across hormone therapy, weight loss, and aesthetics.
How We're Updating Our Patient Recommendations
Based on the new guidelines, here's what we're now actively recommending to patients during intake and follow-ups, where appropriate:
- Minimum 2 resistance training sessions per week — non-negotiable for patients on hormone therapy, GLP-1 medications, or after Emsculpt NEO
- Heavier loads than most patients are using — if you're doing 15+ reps comfortably, the load is too light for strength
- 2-3 sets per exercise, focused and intentional rather than endless sets of moderate effort
- Compound movements first — squats, deadlifts, presses, rows, before isolation work
- Eccentric emphasis — control the lowering phase, 2-3 seconds typical
- Progress the load over time — the same weights forever doesn't produce the same results forever
- Skip the gimmicks — most of the equipment and protocols sold in 2026 don't outperform basic, well-executed compound lifting
None of this requires expensive equipment, fancy gyms, or coaching credentials in exercise science. It requires intentionality and consistency.
What This Means If You're Just Starting
If you're a patient who hasn't been resistance training and is reading this thinking "I don't even know where to start," the honest answer is: start anywhere, but start. The new guidelines are clearest about adults who are already training. For someone beginning at 45 or 55 or 65, the priorities are different and the gains are larger.
For new starters:
- Two sessions per week, total-body
- Five or six compound movements per session — squat variation, hinge variation, press, row, carry, optional core
- 2-3 sets each
- Start lighter than you think; progress within 2-3 weeks
- Working with a trainer for the first month is usually money well spent if you've never lifted before
The patients who benefit most from the new ACSM guidelines are often the ones who haven't been training at all. The data on previously sedentary adults starting resistance work in their 40s, 50s, and 60s is remarkable — the trajectory of physical function changes dramatically once consistent strength work enters the picture.
The bottom line: Resistance training is medicine. The new ACSM guidelines give us the most evidence-rich prescription we've ever had for how to use it. If you're a Defiance patient on hormone therapy, weight loss medication, or pursuing aesthetic body composition changes, this isn't optional anymore — it's the foundation that determines how much your medical care actually accomplishes.
Where We Fit In
We're not a gym, and we don't replace one. What we do is integrate the medical side of your care — hormone optimization, weight loss medication, Emsculpt NEO, comprehensive labs — with realistic guidance on the lifestyle side that actually drives outcomes.
Our Centennial clinic at 7354 S Alton Way is located directly within the Denver Tech Center, just off I-25 at Arapahoe Road. We see patients from across the DTC, Greenwood Village, Lone Tree, Castle Pines, Castle Rock, Highlands Ranch, Cherry Hills Village, Englewood, and Parker. Many are juggling demanding jobs in DTC offices, family logistics, and trying to maintain a real active lifestyle through their 40s, 50s, and beyond.
The new ACSM guidelines are a gift for that population. Clear, evidence-based, free of marketing noise. We're going to be talking about them with our patients for years.
Ready to integrate this into your care plan?
Whether you're already a Defiance patient or considering becoming one, our intake includes specific guidance on resistance training paired with whatever medical care you're pursuing. Our Centennial clinic in the DTC is convenient for patients across the south Denver metro.
Book a ConsultationThis article is for educational purposes only and does not constitute medical advice or individualized exercise prescription. The ACSM Position Stand referenced (Currier et al., Med Sci Sports Exerc, April 2026; PMID 41843416) addresses healthy adults. Patients with medical conditions, recent injuries, or specific limitations should consult with a qualified clinician before starting any new resistance training program. Defiance Health is a cash-pay clinic in Centennial and Alamosa, Colorado, offering bioidentical hormone therapy, medical weight loss, medical aesthetics, and comprehensive labs.