Impact exercise for bone
Impact exercise — hopping, jumping and landing — gives bone the sharp, fast loads it responds to, and short bouts of one-legged hopping raised hip bone density in three small trials, at least two of them with daily hopping. The catch is frequency: in the one trial that compared schedules, hopping twice a week did nothing, and only daily hopping helped. None of these trials measured fractures.
Do about 50 one-legged hops in different directions every day, building up gradually, alongside heavy lifting. If you have already had a spinal fracture or several low-trauma fractures, keep impact to about brisk-walking level instead.
Why impact works
Bone only builds when it is loaded harder or faster than it is used to. In the standard model of how bone adapts, the mechanostat, bone adds mass above one strain threshold and removes it below a lower one, so a load has to be unusual in size, not just repeated often.[1] Walking repeats a modest load thousands of times; a landing delivers a large one in a fraction of a second.
How big the loads are. In 21 premenopausal women with an average age of 43, two-footed star and stride jumps with a bounce straight back up produced landing forces of about 3.90 to 5.38 times body weight, applied at 192 to 329 body weights per second.[2] That is above the thresholds of more than 3 body weights and more than 43 body weights per second that this research uses — though the paper cites those thresholds from earlier work rather than establishing them, so treat them as rough guides. One-legged hops are gentler, at about 2.5 to 2.8 times body weight, below that threshold, yet they still built hip bone when done daily.[3] And not every jump is a big load: in one computer-modelling study, countermovement and squat jumps loaded the hip and ankle less than walking did, while hopping loaded them more.[4]
Different jumps gave a similar short-term marker response. In 29 postmenopausal women, countermovement jumps, drop jumps and diagonal drop jumps each raised a blood marker of bone formation (P1NP) by about 8–11% straight afterwards, with no significant difference between them.[5]
How often: daily, not twice a week
The one trial that tested frequency randomly assigned healthy premenopausal women to 50 multidirectional hops on one leg on 0, 2, 4 or 7 days a week for six months; 61 finished.[6] Femoral-neck density (the top of the thigh bone, where hips break) in the hopping leg changed by:
| Days a week | Change |
|---|---|
| 0 | −0.3% |
| 2 (100 hops a week) | 0.0% |
| 4 | +0.9% |
| 7 | +1.8% |
Only the daily group gained clearly, and the authors concluded that less frequent hopping was not effective. Since the hops were gentle, frequency rather than force seems to have done the work.
Who it has worked for
Two more trials used the same design: hop on one randomly chosen leg and compare it with the other, untrained leg, which largely cancels out differences in diet and lifestyle between people.
- Older men. Fifty healthy older men built up to 50 multidirectional hops, seven days a week, for a year. In the 35 who finished, femoral-neck density rose about 0.7% in the hopping leg and fell about 0.9% in the other. Three of the men who dropped out did so because of discomfort during the exercise.[7]
- Postmenopausal women. Forty-two women aged 55 to 70 did six months of progressive one-legged hops. In the 35 who finished, femoral-neck density rose about 0.8% in the hopping leg and fell about 0.6% in the other. Knee scans by magnetic resonance imaging (MRI) showed no sign that the hopping worsened cartilage or arthritis-related damage.[8]
Impact was also part of the heavy programme in the LIFTMOR trial, in the form of jumping chin-ups with firm drop landings.
What hasn't been tested
- Fractures. All the hopping trials measured density, a stand-in for fracture risk, in small groups over six to twelve months.
- People with osteoporosis. The hopping trials recruited healthy adults, not people with very fragile bones or past fractures.
- Other jumps at the hip. Low box jumps and other jumps have not been tested at the hip the way multidirectional hopping has, and squat-type jumps may load the hip less than walking, so hopping is the better-supported choice.
Who should be careful
A UK expert consensus advises that if you have already had a vertebral fracture or several low-trauma fractures, you should usually keep impact to about the level of brisk walking.[9] Many vertebral fractures cause no symptoms, so a pain-free back does not mean your spine is intact; if you are unsure, ask for an assessment first. Build up the number of hops gradually, as the trials did; discomfort was the reason some participants quit.
What to do
- Hop daily. About 50 one-legged hops in different directions, the dose used in the daily trials.
- Build up gradually rather than starting at the full number.
- Keep lifting. Impact adds to heavy resistance training rather than replacing it; see Bone density.
- Keep going. In one trial of other bone training, the spine advantage was gone three months after stopping; nobody has tested how long hopping gains last.
Further reading
- Bailey CA, Brooke-Wavell K. Optimum frequency of exercise for bone health: randomised controlled trial of a high-impact unilateral intervention. Bone 2010.[10]
- Allison SJ et al. High impact exercise increased femoral neck bone mineral density in older men: a randomised unilateral intervention. Bone 2013.[11]
- Hartley C et al. High-Impact Exercise Increased Femoral Neck Bone Density With No Adverse Effects on Imaging Markers of Knee Osteoarthritis in Postmenopausal Women. J Bone Miner Res 2020.[12]
- Clissold TL et al. Bilateral multidirectional jumps with reactive jump-landings achieve osteogenic thresholds with and without instruction in premenopausal women. Clin Biomech (Bristol) 2020.[13]