Low impact isn’t low effort when water jogging can match a 10-minute mile

Key takeaways

• In people with sensor-equipped knee replacements, a rowing machine pressed on the knee with about 0.9 times body weight and a stationary bike 1.3 times, compared with 2.6 times for walking and 4.2 for jogging².
• Low-impact can be vigorous: the 2024 Adult Compendium rates hard water jogging at 9.8 METs and a hard elliptical session at 9.0, about the same as running a 10-minute mile at 9.3⁶.
• A 2025 BMJ analysis of 217 trials found that aerobic exercise was most likely to ease knee osteoarthritis pain and improve function, with moderate certainty⁴.
• In a 2005 study of older adults with knee arthritis, each pound lost took about 4 pounds of load off the knees during walking, but guidelines count exercise as core treatment with or without weight loss³⁸.
• You can do short, hard intervals on a bike, a rower or in the pool, but in a small trial in knee arthritis, steady cycling eased symptoms just as much as intervals did⁹.

How hard does your knee work when you play golf? Researcher Darryl D’Lima reported the answer using knee replacements that measure their own load².

The shin-bone part of each implant carried force sensors and a wireless transmitter. Over four years after surgery, researchers recorded what the knee felt during daily life, gym machines and sports².

Some results were expected. Jogging pressed on the knee with about 4.2 times body weight, and walking with 2.6 times². Others were not: golf hit 4.4, slightly more than jogging². At the gentle end, a stationary bike measured 1.3, and a rowing machine just 0.9, less than walking across a room².

Those numbers come from replaced knees, reported in a conference abstract, so treat them as a rough guide. But they make a point that matters if your joints ache, you carry extra weight or you’re coming back from injury. Plenty of workouts load your joints lightly and still work your heart hard.

That’s the promise of low-impact movement. We walk through what the term means, what the research shows for sore knees and hips, and a menu of options with real effort numbers.

Low-impact describes how force lands, not how hard you work

There’s no official definition, so here’s ours. A low-impact activity keeps you supported the whole time, by a foot on the ground, a seat, pedals, handles or water. You never leave the ground and land again.

High-impact activities include a flight phase: running, jumping rope, jumping jacks and many sports. Each landing sends a spike of force up through your feet, knees and hips.

Effort is a separate question. The Centers for Disease Control and Prevention (CDC) calls an activity moderate at 3 to 5.9 METs and vigorous at 6 or more⁵. A MET is a unit of energy use, where 1 equals sitting quietly. In plain terms, during moderate activity you can talk but not sing, and during vigorous activity you can say only a few words before you need a breath⁵.

The 2024 Adult Compendium of Physical Activities, a research catalog of 1,114 activities for adults aged 19 to 59, shows how far apart impact and effort can sit⁶¹².

Low-impact aerobic dance at moderate effort rates 4.8 METs⁶. High-impact aerobic dance at vigorous effort rates 8.0⁶. But a hard elliptical session reaches 9.0, and hard water jogging 9.8⁶. Running at 6 miles an hour, a 10-minute mile, rates 9.3⁶.

MET values are averages. Your own effort depends on fitness, technique and how hard you push.

Impact isn’t the enemy, but it isn’t required

Running roughly doubles the peak force on your knee. In a 2020 lab study of 22 healthy young adults, peak force on the inner knee averaged 5.6 times body weight when running and 2.9 times when walking¹.

This is the twist. Runners take longer, fewer strides, so the total load per meter traveled came out the same for both, about 0.64 times body weight for every meter¹. The authors’ model suggested that per-meter math alone can’t explain how knees cope with a lifetime of running, and that cartilage likely adapts to the training it gets¹.

So if you love running and your joints feel fine, low-impact training isn’t a rule you have to follow. It’s a tool. It helps when joints hurt, when you’re carrying more weight, when you’re recovering from an injury, or when you want hard training days without extra pounding.

If bone strength is one of your goals, see our upcoming article on bone strength, which covers the kinds of loading bones need.

Machines differ more than you’d think

Here are the measured peak forces from the sensor-equipped knee replacements, from lightest to heaviest².

Activity	Peak force on the knee (times body weight)
Rowing machine	0.9
Stationary bike	1.3
Knee extension machine	1.5
Elliptical machine	2.3
Walking	2.6
Leg press machine	2.8
Hiking	3.2
Stair-climbing machine	3.3
Jogging	4.2
Tennis or skiing	4.3
Golf	4.4

The abstract doesn’t say how many people were measured². Natural knees, with their own cartilage and ligaments, may behave differently. Still, the ranking gives you a sensible place to start if one machine leaves your knees sore: try one lower on the list.

For arthritic knees and hips, exercise is the core treatment

Osteoarthritis involves the breakdown of the cartilage that cushions a joint. Resting a sore joint can feel like the safe choice. The research points the other way.

In 2019, the Osteoarthritis Research Society International (OARSI) issued guidelines for treating knee, hip and multi-joint osteoarthritis without surgery³. For the knee, its core treatments are education plus structured exercise on land³. That can mean strength, cardio and balance work, or mind-body practice such as tai chi or yoga, with or without a diet plan for weight loss³. For the hip, structured land exercise is the core treatment³.

Water exercise got a weaker, conditional recommendation, partly because pools can be hard to reach and costly³. It still works for many people, and our swimming article covers that research.

A 2025 review in The BMJ went further. A team led by Lei Yan combined 217 randomized trials, covering 15,684 people with knee osteoarthritis, and ranked six types of exercise against each other⁴. Aerobic exercise came out on top for pain, daily function, walking and quality of life, and the evidence for those results was rated moderate in certainty⁴. That category includes walking, cycling and swimming, and the authors proposed it as the first treatment to try¹¹.

Two limits matter. Much of the ranking rests on indirect comparisons, where two kinds of exercise were each tested against a control group rather than against each other¹¹. And only 18% of the trials tracked safety, though those that did found no clear difference in harms⁴.

For readers who prefer to try natural approaches before medicines, this is well-tested ground: guidelines put exercise at the center of treatment³. Our tai chi article in this series, our upcoming arthritis article and our guide to building a wellness plan, which covers the Walk With Ease program, go deeper.

A low-impact menu, rated by effort

This menu is our own, built from Compendium values and the knee-force data²⁶⁷. The effort range runs from easy to hard versions of each activity.

Activity	Effort range (METs)	Joint notes	Equipment	Cost
Brisk walking on level ground	3.8 to 4.86	About 2.6 times body weight at the knee2	Supportive shoes	Free
Stationary bike	4.0 at light effort to 10.3 at hard effort6	Among the lightest knee loads2	Upright or recumbent bike	Gym fee or home machine
Elliptical	5.0 to 9.06	Below walking, no landings2	Machine	Gym fee or home machine
Rowing machine	5.0 to 14.06	Lightest knee load measured2; uses back and arms too	Machine	Gym fee or home machine
Water walking	2.5 to 6.86	Water carries part of your weight	Pool access	Pool fee
Water aerobics	5.5, up to 7.5 for high-intensity classes6	The instructor sets the pace	Pool access	Class or pool fee
Water jogging	9.8 at vigorous effort6	No landings in deep water	Pool, float belt optional	Pool fee
Low-impact aerobics	4.86	One foot stays down	Video or class	Free to class fee
Chair exercise class	About 3.5 to 3.8 for older adults7	Seated, so hips and knees bear little weight	Sturdy chair	Free to class fee
Arm bike (hand cycle)	2.0 to 3.56	Spares the legs entirely	Machine	Gym or rehab setting

Older adults use less energy at rest, so the Compendium keeps a separate older-adult list built on a lower resting baseline⁷. In that list, a hard stationary-bike session at 101 to 160 watts rates 7.8 METs⁷.

Larger bodies: comfort first, weight loss optional

Extra body weight raises the load on your knees as you walk⁸. In 2005, Stephen Messier’s team at Wake Forest University reported on 142 older adults with knee osteoarthritis and overweight or obesity, according to a university news release⁸. The 18-month program trimmed their weight by only 2% on average⁸.

That modest loss still counted. Every pound shed meant about 4 pounds less pressure on the knees while walking, the team found⁸. Scale that up, and the release’s math is striking: lose 10 pounds, and each knee is spared about 48,000 pounds over a mile of walking⁸.

That’s useful, but it isn’t a requirement for starting. OARSI counts exercise as core knee treatment with or without weight loss³. For hip arthritis, it judged weight loss unlikely to ease symptoms much, noting a lack of hip-specific trials³. You can move now, in the body you have, and get the benefits.

A few practical comfort tips (our suggestions, not tested in trials):

• Choose supported options first: a recumbent bike with a wide seat, a pool or a chair class.
• Start with short bouts, such as 10 minutes, and add time before you add speed.
• Ask about weight limits on machines, and look for wide, stable seats and pedals.
• Wear moisture-wicking clothes, and use an anti-chafing balm on long sessions.

Hard intervals without the pounding

Interval training means short bursts of hard effort with easy recovery between them. Our cardio article covers the basics. Low-impact machines make it easier on the joints.

A small 2018 trial tested the idea in people aged 40 to 80 with knee osteoarthritis⁹. Twenty-seven were randomly assigned to cycle at home four times a week for eight weeks, about 25 minutes a session⁹. One group did five 45-second hard efforts, each followed by 90 seconds of easy pedaling. The other rode steadily for 20 minutes⁹.

Both groups’ arthritis symptom scores dropped by more than a third, with no real difference between them⁹. The interval group got quicker on a timed stand-up-and-walk test⁹.

The cautions are real, though. Only 17 people finished, and one person in the interval group logged 24 adverse events from a cyst behind the knee that cycling aggravated⁹. That’s why we rate low-impact intervals for arthritic knees as promising but early, with no proof they beat steady riding. If steady exercise is all you want, it may serve your knees just as well.

If you try intervals, “hard” means you can say only a few words before taking a breath⁵. Rest a day between interval sessions.

A 3-week low-impact sampler

This plan is our own design. It lets you test several options at moderate effort, then pick favorites and add one interval session. Effort numbers use a 0-to-10 feel scale: 3 to 4 means you could chat, 5 to 6 means you can talk but not sing, and 7 means only a few words at a time⁵.

Week	Day 1	Day 2	Day 3	Day 4
1: Try three	Stationary bike, 20 minutes, effort 4	Water walking or water aerobics, 20 to 30 minutes, effort 4	Elliptical or rowing machine, 15 to 20 minutes, effort 4	Rest, or an easy 15-minute walk
2: Pick two	Favorite option A, 30 minutes, effort 5	Strength session from our strength article	Favorite option B, 30 minutes, effort 5	Chair class or easy walk, 20 minutes
3: Add one hard day	Option A, 35 minutes, effort 5 to 6	Strength session	Intervals on option B: 5-minute warm-up, five 45-second efforts at 7 with 90 seconds easy, then easy pace to 30 minutes	Option A or B, 30 minutes, effort 4 to 5

By week 3, you’ll log close to 100 minutes of cardio a week. Our cardio article explains how to build toward the federal weekly goal from there.

Joint check. After each session and the next morning, rate joint pain from 0 to 10. If it’s higher the next day than before you started, drop back to the previous week or switch to an option lower on the knee-force list.

What the evidence shows

Claim	What the research shows	Evidence level
Exercise eases knee osteoarthritis pain and improves function	Core treatment in OARSI 2019; 217 trials in a 2025 review34	Strong evidence
Aerobic exercise is the best type for knee osteoarthritis	Ranked first with moderate certainty, mostly via indirect comparisons4	Promising but early
Low-impact activities can be vigorous	Compendium values of 9 METs or more for hard elliptical, rowing, bike and water jogging6	Strong evidence (measured energy cost)
Rowing and cycling put less force on the knee than walking	Measured directly, but only in replaced knees, in one conference abstract2	Promising but early
Low-impact intervals help arthritic knees	One small trial: symptoms improved, but 10 of 27 dropped out and one person’s knee cyst flared repeatedly9	Promising but early
Low-impact intervals beat steady exercise for arthritic knees	One small trial: no difference in symptoms9	Not enough evidence
Losing weight eases knee load	About 4 pounds less load per pound lost in one study8	Promising but early
You must lose weight before exercise helps	Exercise is core treatment with or without weight loss3	Evidence says no

Questions readers ask

The bottom line

Low-impact movement isn’t a lesser version of exercise. Bikes, rowers, ellipticals and pools can push your heart as hard as running while sparing your joints the landings, and aerobic exercise is among the best-supported ways to ease knee arthritis.

Pick the option your joints like, build time first and intensity second, and save hard intervals for when the basics feel easy. If you have heart disease or a joint that’s swelling, start with a clinician.

Related reading

• Swimming is easy on your joints, and being a safe swimmer takes five skills
• Cycling’s health payoff outweighs city smog, so traffic is the risk to manage
• Low fitness rivals smoking as a health risk, and cardio can change it
• Viral “Japanese walking” was tested in a 2007 trial, and its lesson is about pace
• A good wellness plan fits on one page and changes every season

Sources

1. Miller RH, Krupenevich RL. “Medial knee cartilage is unlikely to withstand a lifetime of running without positive adaptation: a theoretical biomechanical model of failure phenomena.” PeerJ, 2020;8:e9676. pubmed.ncbi.nlm.nih.gov
2. D’Lima D. “Knee Forces During ADL and Sports Activities in TKA Patients.” Orthopaedic Proceedings, 2012;94-B(Supp XL):38. boneandjoint.org.uk
3. Bannuru RR, Osani MC, Vaysbrot EE, et al. “OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis.” Osteoarthritis and Cartilage, 2019;27:1578–1589. esceo.org
4. Yan L, Li D, Xing D, et al. “Comparative efficacy and safety of exercise modalities in knee osteoarthritis: systematic review and network meta-analysis.” BMJ, 2025;391:e085242 (PEDro record). search.pedro.org.au
5. Centers for Disease Control and Prevention. “Measuring Physical Activity Intensity.” Updated December 4, 2025. cdc.gov
6. Herrmann SD, Willis EA, Ainsworth BE, et al. “2024 Adult Compendium of Physical Activities,” activity list. Compendium of Physical Activities, 2024. pacompendium.com
7. Compendium of Physical Activities. “Older Adult Compendium.” Published December 4, 2023, updated March 8, 2024. pacompendium.com
8. Wake Forest University. “Weight loss reduces knee-joint loads” (on Messier SP, et al., Arthritis & Rheumatism, 2005;52:2026–2032). News release, July 6, 2005. news.wfu.edu
9. Keogh JWL, et al. “Is high-intensity interval cycling feasible and more beneficial than continuous cycling for knee osteoarthritic patients? Results of a randomised control feasibility trial.” PeerJ, 2018;6:e4738. pubmed.ncbi.nlm.nih.gov
10. Green DJ. “New Preparticipation Guidelines Remove Barriers to Exercise.” American Council on Exercise, February 2018 (summarizing ACSM’s Guidelines for Exercise Testing and Prescription, 10th ed.). acefitness.org
11. ScienceDaily. Report on Yan L, et al., “Comparative efficacy and safety of exercise modalities in knee osteoarthritis,” BMJ, 2025. April 30, 2026. sciencedaily.com
12. Herrmann SD, et al. “2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities.” Journal of Sport and Health Science, January 2024 (DOAJ record). pubmed.ncbi.nlm.nih.gov