Cardio people and strength people enjoy the argument. Your body isn't participating in it.
The two do genuinely different work, and the most interesting finding in this literature isn't that one wins. It's that the combination is associated with substantially better outcomes than either one on its own, and that the amount of strength work involved is smaller than almost anyone expects.
Key takeaways
Muscle-strengthening activity on its own was associated with 15% lower all-cause mortality across 16 studies (Momma et al. 2022, British Journal of Sports Medicine).
Doing both strength and aerobic activity was associated with 40% lower all-cause mortality compared with doing neither, and 46% lower cardiovascular mortality.
The dose curve peaks early. Maximum association appeared at roughly 30 to 60 minutes a week of strength work, with no added benefit beyond about an hour.
Your tracker will underrate it. No wearable tested met the accuracy threshold for energy expenditure during resistance exercise (Boudreaux et al. 2018, MSSE).
What does strength training do that cardio doesn't?
Different tissue, different timescale, different payoff.
Cardio, meaning brisk walking, cycling, swimming, running, trains the heart, lungs and circulation. It's what makes everyday efforts cost less over time: the same hill, fewer beats. It's also the main driver behind slow shifts in resting heart rate and VO2 max.
Strength work builds and preserves muscle, loads bone, and supports how your body handles glucose. Its payoff is less visible day to day and more visible across decades: carrying shopping, climbing stairs, getting off the floor without planning the manoeuvre.
Here's a concrete illustration of how separate these effects are. A meta-analysis of 191 studies covering 12,952 people found endurance training lowered resting heart rate by roughly 2.7 to 5.8 bpm. Strength training showed no significant effect on resting heart rate at all (Reimers et al. 2018, Journal of Clinical Medicine).
That isn't evidence lifting doesn't work. It's evidence that resting heart rate is a cardio dial, and asking it to report on your strength training is asking the wrong instrument.
Is doing both actually better than doing one?
This is the strongest finding in the area, and the numbers are large.
A systematic review pooled 16 prospective cohort studies on muscle-strengthening activity. On its own, it was associated with meaningfully lower risk across the board (Momma et al. 2022):
Outcome | Association with muscle-strengthening activity |
|---|---|
All-cause mortality | 15% lower (RR 0.85, 95% CI 0.79 to 0.93) |
Cardiovascular disease | 17% lower (RR 0.83, 0.73 to 0.93) |
Diabetes | 17% lower (RR 0.83, 0.77 to 0.89) |
Total cancer | 12% lower (RR 0.88, 0.80 to 0.97) |
Then the combination. Compared with people doing neither strength nor aerobic activity, people doing both showed:
Outcome | Combined vs neither |
|---|---|
All-cause mortality | 40% lower (RR 0.60, 0.54 to 0.67) |
Cardiovascular mortality | 46% lower (RR 0.54, 0.41 to 0.70) |
Cancer mortality | 28% lower (RR 0.72, 0.53 to 0.98) |
Read that second table with appropriate caution. It compares people doing both against people doing neither, which is a wide gap, and people who do both tend to differ in other ways too: they're often healthier to begin with, and illness itself makes people less active. These are observational associations, not the results of assigning people to training programmes.
The reason it's still worth taking seriously is the consistency. The benefit of adding strength work held independently of aerobic activity, across four different outcomes, in sixteen separate cohorts.
How much strength work do you actually need?
Much less than the gym implies. This is the finding most worth internalising.
The dose-response curve was J-shaped, not a straight line, with the strongest associations at surprisingly small amounts (Momma et al. 2022):
Outcome | Peak benefit at | Size at peak |
|---|---|---|
All-cause mortality | about 40 min/week | 17% lower |
Cardiovascular disease | about 60 min/week | 18% lower |
Total cancer | about 30 min/week | 9% lower |
Diabetes | up to about 60 min/week | plateaus after |
Beyond roughly an hour a week, the association flattened and in some cases drifted back. Benefits remained visible up to about 130 to 140 minutes a week.
Forty minutes. That's two twenty-minute sessions, or three short ones. If the barrier to starting has been imagining an hour-long gym routine four times a week, the evidence doesn't ask for that.
The usual caution applies to reading a J-curve from observational data: the apparent decline at very high volumes could reflect who trains that much rather than the training itself. But the shape of the early part of the curve is clear, and the practical message survives either way. Most of the available benefit sits in the first hour.
Why does strength training look so unimpressive in my data?
Because the measurement genuinely can't see it, and this is worth being explicit about.
Fifty people completed graded cycling and three sets of four resistance exercises while wearing eight different consumer devices, with a metabolic analyzer as the reference. The researchers set the bar for validity at 10% mean absolute error. No device met it for energy expenditure during either cycling or resistance exercise (Boudreaux et al. 2018, Medicine and Science in Sports and Exercise).
The reason is structural. Most wearables estimate energy expenditure from heart rate and motion. Resistance training has short work periods, frequent rests, and heart rate that keeps dipping between sets. So a session that left your legs shaking produces modest active energy and few exercise minutes.
Add the sensor problem on top: wrist optical monitors showed about 4.7% error during weight training against a chest strap, worse than during cycling or jogging, because gripping and bracing disrupt the optical signal (Schweizer and Gilgen-Ammann 2025, JMIR Cardio).
The conclusion isn't that your data is useless. It's that your metrics have a blind spot, and you shouldn't let them pick your training. Cardio moves the visible dials because the visible dials were built to measure cardio. Strength does much of its work in muscle and bone that no wrist sensor counts.
If your charts flatter your walking and shrug at your lifting, both still happened.
What does a realistic mix look like?
Current guidance for adults is 150 to 300 minutes of moderate aerobic activity a week, or 75 to 150 vigorous, plus muscle-strengthening activity on two or more days (Physical Activity Guidelines for Americans).
Set against the dose-response data, a workable shape is:
Most days: some brisk movement. Walking counts, and adding a thousand steps is a reasonable place to start. Keep most of it conversational, per heart rate zones.
Two days a week: something your muscles notice. Twenty minutes of squats, push-ups and rows at home clears the volume the evidence points to. Heavy gardening and digging counted in these cohorts too.
Judge it over weeks. Look at your last fortnight and ask one question: is either ingredient missing entirely? That's the only comparison that matters, and it's the compare-you-to-you principle applied to training.
The honest framing is that this isn't a competition with a winner. It's two different jobs, one of which your tracker can see clearly and one of which it mostly can't.
Frequently asked questions
Is cardio or strength training better for health?
Neither, on the available evidence. Muscle-strengthening activity alone was associated with 15% lower all-cause mortality, and the association held independently of aerobic activity. But people doing both showed 40% lower all-cause mortality than people doing neither (Momma et al. 2022). The combination outperformed either component.
How many minutes of strength training per week?
Less than most people assume. The association with all-cause mortality peaked at about 40 minutes a week, and cardiovascular benefit at about 60, with no clear additional benefit beyond roughly an hour (Momma et al. 2022). Public guidance frames this as muscle-strengthening on two or more days a week.
Why doesn't my watch count my weight training?
Because it can't measure it accurately. Across eight consumer devices tested against a metabolic analyzer, none met the 10% accuracy threshold for energy expenditure during resistance exercise (Boudreaux et al. 2018). Wearables estimate energy from heart rate and motion, and lifting has short efforts with frequent rests, so heart rate keeps dropping between sets.
Does strength training lower resting heart rate?
Not meaningfully on its own. A meta-analysis of 191 studies found endurance training and yoga reduced resting heart rate significantly, while strength training showed no significant effect overall (Reimers et al. 2018). That's a limitation of resting heart rate as a measure of strength work, not a limitation of strength work.
Can I get strength benefits without a gym?
The cohort studies behind these findings counted bodyweight exercises, resistance bands and heavy gardening such as digging alongside conventional weight training (Momma et al. 2022). Given that the dose associated with peak benefit was roughly 30 to 60 minutes a week, a short home routine twice a week is within range.
Knit shows patterns, not diagnoses. Talk to a clinician about readings that concern you.
