Strength training

• Build and keep muscle mass and strength across adult life.
• Slow age-related loss of bone density and lower fracture risk.
• Keep physical function: rising from a chair, climbing stairs, carrying shopping, balance.
• Improve blood pressure, blood sugar control and body composition.
• Lower the risk of early death, together with aerobic exercise.
• Reduce sports injuries and support mood.

The terms overlap. Resistance training and weight training describe the method. Strength training in the narrow sense aims at the most force you can produce, usually with heavy loads and few repetitions, while hypertrophy training aims at muscle size with more sets in the moderate range. For health, the distinction matters less than people think: a review of 137 systematic reviews by the American College of Sports Medicine found that most programs improve strength, size, power, balance and gait speed compared with doing nothing [3].

Three features make it a protocol rather than just activity:

• Effort. Sets end close to the point where another clean repetition would not be possible.
• Coverage. The program works all major muscle groups: legs, hips, back, chest, shoulders, arms and trunk.
• Progression. Load, repetitions or sets rise as the body adapts, which is called progressive overload.

Public health guidelines treat it as a separate requirement from cardio. WHO recommends regular muscle-strengthening activity for every age group on top of 150 to 300 minutes of moderate aerobic activity a week [20], and the NHS asks adults to do strengthening activity that works all major muscle groups on at least 2 days a week. If you train for muscle size specifically, the app's hypertrophy protocol sets weekly volume targets.

The best known number comes from a 2022 meta-analysis of 16 cohort studies. Muscle-strengthening activity was linked to 10 to 17% lower risk of death, cardiovascular disease, cancer and diabetes, and the largest reduction, about 10 to 20%, sat at 30 to 60 minutes a week [1]. A second 2022 meta-analysis found the peak at about 60 minutes a week, a 27% lower risk of death from any cause, with smaller reductions at higher volumes [2].

Trials of strength itself agree that the floor is low. In trained men, a single set of 6 to 12 repetitions at about 70 to 85% of one-repetition maximum (1RM), 2 to 3 times a week, raised 1RM strength [10]. In an interview, hypertrophy researcher Brad Schoenfeld put the minimum effective dose for muscle growth at about 4 hard sets per muscle per week. Reviews of older adults reach the same conclusion: about 60 minutes or less across 2 days, on simple machines, delivers most of the benefit [21].

Few people reach even the minimum. In a US survey of 30,162 adults aged 65 and older, only 9.6% reported strength training twice a week [23].

The 2026 ACSM position stand summarizes the variables that changed results across hundreds of trials [3]:

• Strength rose most with heavier loads (80% of 1RM or more), a full range of motion, 2 to 3 sets, lifting early in the session and 2 or more sessions a week.
• Size rose most with higher volume (10 or more sets a week) and with eccentric overload, the lowering phase done under heavier load.
• Power rose most with moderate loads (30 to 70% of 1RM) lifted fast.
• Training to complete failure, the type of equipment, time under tension and periodization did not consistently change outcomes.

Load and size are less tied than gym lore suggests. Heavy loads win for maximal strength, but muscle growth is similar across a wide range of loads when sets are taken close to failure [4]. In a biopsy study, sets at 30% of 1RM taken to failure raised muscle protein synthesis as much as sets at 90% of 1RM [24]. Lighter loads are a reasonable choice for joints that dislike heavy weights, at the cost of longer sets.

Each extra weekly set adds roughly 0.37% to muscle growth in the dose-response data [22], so volume is the main dial for size. Frequency matters mostly as a way to fit that volume in: with the same weekly sets, training a muscle once or three times a week gave similar growth [25].

Progressive overload in practice

Pick a load you can lift 6 to 12 times with good form. When you reach the top of that range on every set, add the smallest available step of load and drop back to the bottom of the range. Write it down; a training log is the simplest way to know you are progressing.

Three meta-analyses point the same way. Any resistance training was linked to 15% lower all-cause mortality [2]; another analysis of 370,256 adults found 21% lower mortality, and 40% lower when combined with aerobic exercise [7]. A pooled analysis of 11 British cohorts found 23% lower all-cause and 31% lower cancer mortality with any strength exercise [11].

The details are less tidy than the headlines:

• Cardiovascular death links are weaker and less consistent than for aerobic exercise. In one meta-analysis the link was borderline [7], and in the British cohorts the cardiovascular benefit came from aerobic activity [11].
• More is not clearly better. The curves are J-shaped, with the benefit shrinking beyond about 60 minutes a week [1][2]. That may reflect how people report long sessions, or real diminishing returns; nobody knows yet.
• Self-report and confounding. Exposure is usually one survey question. People who lift tend to be leaner, richer and more active in other ways, and adjustment never removes all of that.

What the evidence supports is a combination. The lowest risk in every analysis belongs to people who do both aerobic and muscle-strengthening activity [1][7]. Pair strength work with cardio such as zone 2 training, as longevity programs like the app's longevity focus do.

In the PURE study of 139,691 adults across high, middle and low income countries, each 5 kg reduction in grip strength was linked to 16% higher all-cause mortality and 17% higher cardiovascular mortality, and grip predicted death better than systolic blood pressure [5]. UK Biobank, with 502,293 adults, found 20% higher all-cause mortality in women and 16% in men per 5 kg lower grip, and set weakness thresholds at below 26 kg for men and 16 kg for women [26].

Grip works as a marker because it is easy to test and tracks whole-body strength. Physician Peter Attia makes the same point: he treats grip as a proxy for being strong overall and trains it through carries, pulls, deadlifts and hangs rather than with hand grippers. A higher grip number from squeezing a gadget would not necessarily carry the same meaning as one earned through full-body training.

If you track grip with a hand dynamometer, test the same hand, posture and time of day each time, take the best of three tries, and compare yourself against your own past results more than against cohort averages.

Muscle loss with age is gradual but steady, at about 3 to 8% per decade in inactive adults [12]. Across 49 studies of adults aged 50 and older, resistance exercise added about 1.1 kg of lean body mass, with larger gains from higher-volume programs and smaller gains in the oldest groups [9]. A Cochrane review of 121 trials found a large effect on strength and better gait speed and chair rising in older adults [8], and the National Strength and Conditioning Association recommends supervised, progressive training for older adults [27].

Bone needs heavy, specific loading

Bone responds to high strain applied quickly, which light exercise does not provide. The LIFTMOR trial randomized 101 postmenopausal women with low bone mass to twice-weekly, 30-minute supervised sessions of heavy resistance and impact training at 5 sets of 5 repetitions above 85% of 1RM, or to low-intensity home exercise [6]. After 8 months:

Belinda Beck, who led LIFTMOR, stresses that the program was supervised and progressed carefully; people at high fracture risk should not copy it alone. The rucking guide covers whether loaded walking adds a bone stimulus, and the high-protein diet and creatine guides cover the nutrition that supports muscle gain.

Two points stand out. First, isometric exercise, such as wall squats and hand-grip holds, produced the largest blood pressure drops of any exercise type in a network meta-analysis of 270 trials [13]. Second, strength training on its own is a weak tool for weight loss; its value is in keeping muscle while fat comes off, which is why it pairs with calorie restriction [17]. For blood sugar, the HbA1c and fasting insulin guides explain what the numbers mean.

One result points the other way. A meta-analysis of 8 small trials found that resistance training raised arterial stiffness by about 14% in young adults, though not in middle-aged adults [15]. The finding is small and old, but it is one reason guidelines pair lifting with aerobic exercise rather than replacing it.

In randomized trials of athletes, strength training programs reduced sports injuries to about one third of the rate in controls (relative risk 0.338), and more volume meant fewer injuries [19]. In LIFTMOR, heavy lifting in women with low bone mass produced one minor adverse event [6]. The Cochrane review of older adults did note that trials often fail to report harms well [8], so the true rate of minor strains is uncertain.

The rare serious problem is exertional rhabdomyolysis, where damaged muscle floods the blood with creatine kinase and myoglobin. A case report describes a healthy 37-year-old man with creatine kinase of 95,100 U/L and dark urine after an intense resistance session; he recovered with intravenous fluids [28]. It usually follows a big jump in volume, often in new or returning lifters, and dark urine with severe muscle pain needs same-day medical care.

Practical rules that remove most risk: start with loads you can lift for 12 or more clean repetitions, progress gradually, learn the main lifts from a qualified coach, and avoid holding your breath through long heavy efforts if you have high blood pressure.

• Sets that stop far from failure, so the muscle never gets a real stimulus.
• Adding load faster than form allows, especially on squats and deadlifts.
• Skipping legs and hips, the muscles that matter most for function with age.
• A big jump in volume after a break, the usual setting for severe soreness and rhabdomyolysis.
• Replacing all cardio with lifting, which leaves aerobic fitness and heart benefits on the table.
• Changing the program every week, which makes progress impossible to measure.

• have uncontrolled high blood pressure, recent heart symptoms or a heart condition
• have osteoporosis with a history of fractures and plan heavy lifting (seek a supervised program)
• are recovering from surgery, a hernia or a recent musculoskeletal injury
• are pregnant and new to lifting
• have had rhabdomyolysis before or take medicines that affect muscle, such as some statins, and notice unusual muscle pain

• Delayed-onset muscle soreness for 1 to 3 days, worst in the first weeks.
• Joint and tendon aches if load rises too fast.
• Low back strain from poor hip hinge technique.
• Rarely, exertional rhabdomyolysis: severe muscle pain, swelling and dark urine after an extreme session, which needs urgent care.
• A temporary rise in blood creatine kinase after hard sessions, which can affect blood test results.