What the evidence shows for strength and fitness
US guidelines set clear weekly minimums for strength and aerobic activity4. The studies behind the link with lower death rates were rated very low to moderate in certainty12. A five-year exercise trial in older adults found no statistically significant difference in deaths5.
Strength training. A 2022 systematic review and meta-analysis in the British Journal of Sports Medicine pooled 16 prospective cohort studies of adults aged 18 to 971. Most of the studies were from the US, with others from England, Scotland, Australia and Japan1. People who reported any muscle-strengthening activity had a 15% lower risk of death from any cause than people who reported none1. That estimate pooled seven studies and about 263,000 people (risk ratio 0.85, 95% CI 0.79 to 0.93)1. They also had a 17% lower risk of cardiovascular disease and of diabetes, and a 12% lower risk of total cancer1. There was no clear association with colon, kidney, bladder or pancreatic cancer1.
Aerobic fitness. Cardiorespiratory fitness means aerobic capacity, and VO2max is its laboratory measure. A 2024 overview in the same journal combined 26 systematic reviews with meta-analyses2. Together they covered more than 20.9 million observations from 199 cohort studies2. Adults in the highest fitness group had roughly half the risk of death from any cause of those in the lowest group (hazard ratio 0.47, 95% CI 0.39 to 0.56)2. Each 1-MET higher level of fitness was linked with an 11% to 17% lower risk2.
A Cleveland Clinic cohort study tracked 122,007 adults referred for treadmill testing, with a median follow-up of 8.4 years3. People in the bottom quarter of fitness for their age and sex had about five times the adjusted risk of death of the top 2.3% (hazard ratio 5.04, 95% CI 4.10 to 6.20)3. That gap was larger than the ones linked to smoking (hazard ratio 1.41) or diabetes (1.40) in the same analysis3. The authors reported no upper limit to the benefit of higher aerobic fitness3. Death rates were lowest in the elite group, the top 2.3%3.
Doing both. Three cohort studies in the 2022 meta-analysis looked at people who did both muscle-strengthening and aerobic activity1. People who did both had a 40% lower risk of death from any cause than people who did neither (risk ratio 0.60, 95% CI 0.54 to 0.67)1.
How much exercise is enough?
The benchmark for adults comes from the 2018 Physical Activity Guidelines for Americans, published by the US Department of Health and Human Services4. The aerobic target is 150 to 300 minutes a week of moderate-intensity activity or 75 to 150 minutes of vigorous activity, ideally spread through the week4. An equivalent mix of the two also counts4. On top of that, the guidelines call for muscle-strengthening activity on 2 or more days a week4. It should be of moderate or greater intensity and work all major muscle groups4. Older adults are advised to make their activity multicomponent, adding balance training to aerobic and strength work4.
The guidelines stress that some activity is better than none. They report that people who do about 150 minutes a week have a 33% lower risk of death from any cause than people who aren’t physically active4. A large benefit comes from moving from inactivity to even some activity below the target4. Further benefits accrue beyond 300 minutes, and there’s no evidence of increased risk at 3 to 5 times the guideline amount4.
For strength work, the 2022 meta-analysis linked modest weekly volumes with the largest risk reductions1. Risk of death from any cause was lowest at about 40 minutes a week (17% lower)1. For cardiovascular disease the low point was about 60 minutes (18% lower), and for total cancer about 30 minutes (9% lower)1. That much fits within two short sessions a week, in line with the guidelines’ two-day minimum.
| Activity | Weekly amount | What it is based on |
|---|---|---|
| Moderate aerobic activity | 150 to 300 minutes | US guidelines4 |
| Vigorous aerobic activity | 75 to 150 minutes, or a mix with moderate | US guidelines4 |
| Muscle-strengthening, all major muscle groups | 2 or more days | US guidelines4 |
| Muscle-strengthening, largest observed risk reduction (death from any cause, cardiovascular disease, total cancer) | About 30 to 60 minutes | 2022 cohort meta-analysis1 |
Is zone 2 the best training intensity?
Zone 2 usually means steady, low-intensity exercise below the lactate threshold6. Popular media have positioned it as the optimal intensity for improving mitochondrial and fat-oxidation capacity6. A 2025 narrative review in Sports Medicine assessed zone 2 training in the general population6. It found that the popular recommendations largely stem from observational data from elite endurance athletes who do large volumes of zone 2 training6.
The authors concluded that current evidence doesn’t support zone 2 as the optimal intensity for improving mitochondrial or fat-oxidation capacity6. They wrote that the evidence suggests prioritizing intensities above zone 2 is critical to maximize cardiometabolic benefits, particularly when training volumes are lower6. A narrative review is an expert synthesis rather than a pooled analysis, so it carries less weight than a systematic review.
The mortality evidence is framed differently. The cohort studies rank people by measured fitness or reported activity, not by the intensity zone they trained in12. The US guidelines count both moderate and vigorous minutes4. The targets run in parallel: 150 to 300 moderate minutes or 75 to 150 vigorous minutes, or an equivalent combination4.
Generation 100, a Norwegian trial, compared training intensities with death as the primary outcome5. It randomized 1,567 adults with a mean age of 72.8 in Trondheim, Norway5. For five years, one group was prescribed two weekly sessions of high-intensity intervals: four 4-minute bouts at about 90% of peak heart rate5. A second group was prescribed two weekly 50-minute sessions of continuous moderate exercise at about 70% of peak heart rate5. A control group was told to follow national activity guidelines5.
Deaths were 3.0% in the interval group, 5.9% in the moderate group and 4.7% in the control group5. None of the differences was statistically significant (intervals versus control, hazard ratio 0.63, 95% CI 0.33 to 1.20)5.
Taken together, the evidence is consistent with building aerobic fitness by any route the guidelines count. It doesn’t show that steady low-intensity training is uniquely protective. In the cohort data, what tracks with lower risk is each 1-MET higher level of fitness2. And the 2025 review’s authors favor including some work above zone 2 if your training time is limited6.
What the evidence does not show
It doesn’t show cause and effect. Every study in the 2022 strength meta-analysis was observational, and activity was self-reported1. Most data came from the US, and publication bias couldn’t be tested1. Given these limits, the authors note the pooled estimates may be overstated1. They rated the certainty of the evidence very low for death from any cause, cardiovascular disease and cancer, and low for diabetes1.
The 2024 fitness overview rated certainty very low to moderate2. It judged 11 of its 26 reviews to be of critically low quality and drew mostly on male or male-majority samples2. The Cleveland Clinic study was an observational cohort of patients referred for treadmill testing at one center3. So it can show an association but not cause and effect3.
It doesn’t show that more strength training is always better. The associations in the 2022 meta-analysis were J-shaped1. Estimated risk stayed below that of people doing no muscle-strengthening activity up to about 130 to 140 minutes a week1. The authors concluded that the effect of higher volumes is unclear and that higher volumes may call for caution1. They didn’t identify a specific harm and called for large studies of high-volume training1.
It doesn’t show that a structured training program extends life beyond general activity advice. In Generation 100, the two exercise groups combined didn’t have lower mortality than the control group, which had been told to follow national activity guidelines5. The authors pointed to the control group’s high activity level as one reason the differences between groups were small5. The trial enrolled Norwegians in their 70s. Its wide confidence intervals also leave room for a modest effect that it couldn’t detect.
It doesn’t show anything about specific equipment. The studies measured what people did or how fit they were, not what they owned12. None of the studies reviewed here compared types or brands of equipment.
What home equipment is worth buying
Equipment matters only to the extent that you use it often enough to meet the weekly targets. The guidelines count weights, resistance bands and body-weight exercises such as push-ups as muscle-strengthening activity4. They describe its intensity as how much weight or force you use relative to how much you can lift4. So adjustable dumbbells, a set of bands or body-weight work can all meet the two-day strength target, as long as the load is challenging for you4.
For aerobic work, the guidelines set targets by intensity and time, not by type of activity4. They define moderate activity, such as brisk walking, as 3.0 to less than 6.0 METs4. Vigorous activity, such as jogging or running, is 6.0 METs or more4. A rower, bike or treadmill can all get you there. The better choice is the one that suits your joints, space and noise limits, and that you’ll use most weeks.
- Adjustable dumbbells: check the top weight against what leg and back exercises will need as you get stronger, the smallest weight jump, how the lock works and the cradle’s footprint
- Resistance bands: look for several resistance levels and a secure anchor for the door or frame you plan to use
- Rowers and bikes: check the user weight limit, seat and handle adjustment for your height, the footprint in use and in storage, and how loud the resistance system is
- Treadmills: look for a safety key or lock that stops the belt from starting, and put the treadmill where children and pets can’t reach it (one model was recalled in 2021 after a child was pulled under it and died)7
- Displays: a readout of time, distance, watts or heart rate helps you track effort, but you don’t need one to meet the guidelines
- Warranty and returns: before ordering a large machine, read the frame and parts warranty and check for any restocking or freight-return fees
Safety when you train at home
The US guidelines say physical activity can be safe for almost everyone, and that its health benefits far outweigh the risks of adverse events4. Their advice is to choose activities that suit your current fitness and health goals, and to increase activity gradually4. If you’re inactive, that means starting low and going slow4. They also advise using appropriate gear and equipment in a safe environment4. If you live with chronic conditions or symptoms, they advise being under the care of a health care provider4. Training alone at home means no coach checks your form or effort, which is one reason that gradual build-up matters.
Motorized treadmills carry a specific home hazard. In 2021 the US Consumer Product Safety Commission announced the recall of about 125,000 units of one connected treadmill model7. The recall followed the death of a 6-year-old child who was pulled under the rear of the machine7. The company had received 72 reports of adults, children, pets or objects being pulled underneath, including 29 reports of injuries to children7. Owners of the recalled model were told to stop using it immediately and contact the company for a refund7. If you’re buying any used machine, check recall listings first.
Sources
- Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies British Journal of Sports Medicine, 2022 · meta-analysis
- Cardiorespiratory fitness is a strong and consistent predictor of morbidity and mortality among adults: an overview of meta-analyses representing over 20.9 million observations from 199 unique cohort studies British Journal of Sports Medicine, 2024 · systematic review
- Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing JAMA Network Open, 2018 · cohort study
- Physical Activity Guidelines for Americans, 2nd edition US Department of Health and Human Services, 2018 · guideline
- Effect of exercise training for five years on all cause mortality in older adults—the Generation 100 study: randomised controlled trial BMJ, 2020 · randomized trial
- Much Ado About Zone 2: A Narrative Review Assessing the Efficacy of Zone 2 Training for Improving Mitochondrial Capacity and Cardiorespiratory Fitness in the General Population Sports Medicine, 2025
- Peloton Recalls Tread+ Treadmills After One Child Died and More than 70 Incidents Reported US Consumer Product Safety Commission, 2021 · regulator
How this was written. Written from the sources listed above, checked . It is general information, not medical advice. Talk to a clinician before acting on anything here if you have a health condition or take medication.
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