Weight-bearing and resistance exercise build bone density. Swimming does not. This confuses a lot of people because swimming is genuinely excellent exercise — cardio, muscle, joint protection, mental health. Just not for bones. Here's why, and what the evidence actually shows for each type of activity.
Bone remodels continuously in response to mechanical loading. When bone tissue is stressed — by ground reaction forces, muscle pull, or impact — osteoblasts (bone-building cells) respond by depositing new bone. The greater the load and the more varied the direction of force, the stronger the remodelling signal.
Water buoyancy removes the two key drivers: body weight is supported by the water, eliminating ground reaction forces, and impact is eliminated entirely. A swimmer's skeleton sees very little mechanical challenge. The heart and lungs work hard; the bones do not.
This isn't a knock on swimming. If you have severe arthritis, recovering from injury, or find land-based exercise impossible, swimming is an excellent choice for cardiovascular fitness and muscle maintenance. The point is simply that it won't preserve or build bone density.
Free weights, weight machines, resistance bands — anything requiring muscles to contract against a meaningful load. The bone response comes primarily from the pulling forces muscles exert on bone attachment points, not just from ground impact.
A 2015 meta-analysis by Zhao et al. (37 RCTs, published in Osteoporosis International, PMID 25690914) found resistance training produced average BMD gains of 1–2% at the lumbar spine and 0.5–1.5% at the femoral neck. In an older population where 0.5–1% per year is being lost, this is clinically meaningful.
Dose matters. Studies consistently show that intensities below 70% of one-rep maximum produce minimal bone response. The bone adapts to the peak stress it encounters — low-resistance band exercises that feel challenging but aren't mechanically demanding don't cross that threshold. Squats, deadlifts, hip thrusts, Romanian deadlifts, and leg press directly load the spine and hip — the two sites that fracture most often in osteoporosis.
Jogging, jump rope, stair climbing, hiking with a loaded pack, and dancing all generate ground reaction forces that travel up through the skeleton. The hip and lumbar spine benefit most because they absorb these forces directly.
A 2012 study by Deere et al. (Journal of Bone and Mineral Research, PMID 22190042) found that high-impact loading with an odd-direction element — side-to-side forces, not just straight vertical — was the most effective type for bone stimulation. This is part of why sports like basketball and tennis show stronger bone benefits than straight-line running alone.
Studies in perimenopausal women have shown that jogging 2–3 times per week maintains hip BMD compared to measurable decline in non-exercising controls. The effect is strongest when started before significant bone loss has occurred.
Walking is low-impact exercise that produces ground reaction forces, but at an intensity well below the threshold that maximally stimulates bone. It's better than being sedentary, but the evidence for walking as a standalone bone-preservation strategy is weak, particularly in post-menopausal women.
A 2015 Norwegian randomised trial found that walking alone, without supplementary resistance training, did not produce statistically significant changes in BMD over 12 months in post-menopausal women. Walking's greatest contribution to fracture prevention is indirect: it improves balance, proprioception, leg strength, and reaction time — all of which reduce fall risk, and falls cause fractures.
Combined with resistance training, walking is valuable. As a standalone bone health strategy, it's insufficient.
The evidence here is consistent across multiple reviews. Sanchis-Moysi et al. (2010) found no significant BMD advantage in competitive swimmers compared to non-athletic controls. Chen et al. (2016, PLOS ONE) reviewed studies across aquatic exercise types and found no meaningful BMD gains compared to land-based controls.
Some research has found that competitive swimmers actually have lower BMD than age-matched athletes in land-based sports — not because swimming is harmful, but because years of training in a weight-supported environment may mean less osteogenic stimulus over the athlete's lifetime. This does not mean recreational swimming harms bones; the comparison is athletes vs. athletes, not swimmers vs. sedentary people.
| Activity | Bone Density Effect | Best Evidence Sites | Other Benefits |
|---|---|---|---|
| Resistance training | Strong positive (+1–2% lumbar, +0.5–1.5% hip) | Lumbar spine, hip | Muscle mass, metabolic health, fall prevention |
| Impact activities (jogging, jump rope) | Moderate positive | Hip, spine | Cardiovascular, balance |
| Walking | Minimal alone; better combined | Hip (modest) | Balance, fall prevention, overall health |
| Swimming | No significant effect | N/A | Cardiovascular, muscle, joint-friendly |
Gym access in Canada is affordable at most price points. Planet Fitness memberships run approximately CAD $25/month. YMCA memberships typically range from $50–80/month and include access to group fitness classes. Most municipal recreation centres offer subsidised rates for adults over 60 or 65 — contact your city or town directly, as rates vary considerably.
If swimming is your primary exercise because of joint pain, disability, or personal preference: don't stop. Add calcium (1,000–1,200 mg/day depending on age) and vitamin D (1,000–2,000 IU/day, especially through Canadian winters), talk to your GP about your fracture risk, and consider fall prevention training.
Walking remains valuable even if it's not the most potent bone stimulus. The balance and proprioceptive benefits are real, and falls cause fractures. A person who walks daily and lifts weights twice a week is doing far more for their skeleton than someone who only lifts.
Not all resistance exercise is safe if you already have osteoporosis. Spinal flexion under load — think sit-ups, bent-over rows, or picking up heavy objects with a rounded back — can create compressive forces that fracture vertebrae that are already structurally compromised. This risk is real and documented.
A physiotherapist who works with osteoporosis patients can design a bone-loading program that avoids contraindicated movements, starts at appropriate intensity, and progresses safely. This is worth the time and cost of a few sessions. Many provincial physiotherapy colleges maintain therapist directories searchable by speciality.