Why Strength Training May Be the Most Important Thing Runners Can Do for Their Bones
Most runners think about bone health in terms of mileage. More running, more impact, stronger bones. The logic is clean and feels intuitive. It is also incomplete in ways that matter clinically.
This post covers three things. First, why running alone is not a complete bone health strategy and what the research says bones actually respond to. Second, what the evidence now shows about lifting during pregnancy, because the conversation has shifted significantly and most guidelines have not caught up. Third, the specific training parameters that determine whether a strength program actually drives bone adaptation or just provides general fitness benefit without meaningful skeletal loading.
These are not separate topics. They are the same argument applied to different populations. Capacity built deliberately, with the right inputs, applied consistently over time, is what protects the body against the demands placed on it.
Part One: Running Is Not Enough
Bones Respond to More Than Impact
There are three common beliefs about running and bone health, and all three are at least partially wrong. The first is that running builds strong bones because of the impact. The second is that running is hard on joints and bones and causes long-term damage. The third is that running is roughly neutral for bone health. The research gives us something more specific and more useful than any of those.
Running does stimulate bone adaptation, particularly in newer runners or those meaningfully increasing their training load. But this effect has a ceiling, and most experienced runners have already reached it. Running is not bad for bones. It is simply not sufficient on its own to keep driving adaptation once the skeleton has accommodated to it.
Bones respond to two kinds of mechanical loading: impact forces and muscular contraction forces. A 2017 review by Hart et al. showed that muscle contractions during resistance training can place very large forces on bone, forces that rival or exceed those generated by ground impact (Hart et al., 2017). Progressive resistance training provides a powerful stimulus through exactly that mechanism. The important word is progressive. A 2020 meta-analysis by Grgic et al. found no significant difference in bone mineral density outcomes between high-load and lower-load training, provided effort was adequate and the stimulus was novel (Grgic et al., 2020). Load magnitude matters. So does accumulated muscular tension. So does training variety. The common thread is that the signal to bone must be something the skeleton has not yet accommodated to.
Activity vs. Intentional Capacity Building
Here is a distinction worth stating clearly, because it comes up constantly in practice. Activity and intentional capacity building are not the same thing. Running, walking, and playing sport are forms of activity. They use what the body has already built. They are not reliable mechanisms for continuing to build more of it once the body has adapted to that level of demand.
Someone who runs 40 miles a week or walks several miles a day often assumes their legs and bones are strong because of it. What the research shows is that after accommodation, the signal to keep adapting diminishes. Over time, high-volume activity without progressive overload can become more catabolic than anabolic, drawing on available capacity without replenishing it. Intentional resistance training is what builds the structural reserve that activity draws on (Scofield and Hecht, 2012).
The Saturation Problem
Bone cells do not respond indefinitely to repetitive loading. They habituate. Research suggests the osteogenic response begins to plateau after roughly 40 to 100 loading cycles per session (Rubin and Lanyon, 1984). A single 10-kilometer run produces thousands of ground contact cycles, well past that threshold. The adaptation signal stops being triggered.
This also explains something many high-mileage runners have experienced but could not explain: running consistently for years but still showing low bone mineral density on a scan. More running was never going to solve a problem created by habituation to running. Progressive resistance training delivers a different and genuinely escalating stimulus that the skeleton has not accommodated to, which is what keeps the osteogenic signal active.
Why the Bar Is Higher for Runners
The threshold for what counts as a sufficient loading signal scales with an athlete's habitual loading environment. Swimmers and cyclists gained bone mineral density when plyometrics were added to their training, because the stimulus exceeded what their sport typically demanded. Soccer players in the same study did not, because the loading stimulus did not exceed the demands of a sport already built on high-impact movement.
Runners sit between those two groups. Their skeletons have adapted to significant repetitive impact. The bar for what constitutes a novel and sufficient stimulus is higher than it is for a sedentary individual. More running does not clear that bar. Progressive resistance training does (Piasecki et al., 2018).
Part Two: Lifting During Pregnancy
The Old Guidelines Were Not Evidence-Based
For decades, standard clinical guidance told pregnant women to avoid heavy lifting. The concerns were theoretical: elevated intra-abdominal pressure, potential reduction in blood flow to the fetus, increased risk of musculoskeletal injury. The precaution was reasonable when evidence was scarce. That is no longer the case.
A 2025 systematic review and meta-analysis by Prevett et al., published in the British Journal of Sports Medicine, evaluated resistance training across pregnancy and measured outcomes including gestational hypertension, preeclampsia, gestational diabetes, perinatal mood disorders, cesarean section rates, perineal tearing, labor length, and fetal outcomes including birth weight and gestational age (Prevett et al., 2025). The results were consistent: women who participated in resistance training during pregnancy showed better outcomes across nearly every measure, with no evidence of increased fetal risk.
A 2023 study by Prevett et al. in the International Urogynecology Journal examined what happened when women continued heavy resistance training at loads exceeding 80 percent of their one-repetition maximum through pregnancy. Those women had fewer delivery complications than those who reduced or stopped training. Postpartum outcomes were equally striking: lower rates of anxiety, depression, urinary and anal incontinence, and diastasis recti, and higher rates of return to training (Prevett et al., 2023).
What the Evidence Actually Shows
The data now available consistently supports resistance training throughout uncomplicated pregnancy. A 2024 review found that resistance training during pregnancy helps alleviate common symptoms including fatigue, lower back pain, and poor mental health, and assists with glucose regulation in women diagnosed with gestational diabetes.
Pregnancy places substantial physiological demands on the body. A body that has been building capacity progressively through those demands is better prepared to handle them than one that was progressively deconditioned in the name of caution. Labor and delivery are physical events. Strength built during pregnancy does not disappear after delivery. It is the foundation the recovery is built on.
The Clinical Picture
At ZPO, we see this consistently. Athletes who maintain training through pregnancy with appropriate modifications tend to recover faster postpartum, feel more capable in the early weeks and months, and return to sport more efficiently. That clinical pattern now has a systematic evidence base behind it.
The question is no longer whether lifting during pregnancy is safe. For most women with uncomplicated pregnancies, under appropriate guidance, the evidence says it is not just safe but beneficial. The question is how to dose it intelligently across each trimester and how to continue building capacity without ignoring the real demands the body is simultaneously managing.
Women with high-risk pregnancies, specific contraindications, or concerns should work directly with their obstetric team. This is not a blanket prescription for every situation. It is a call to update the default assumption.
Part Three: The Parameters That Actually Make It Work
Load Magnitude
Based on the work of Fuchs et al. (2001), Hong and Kim (2018), Blagrove et al. (2024), and Zhao et al. (2025), loading at or above 70 percent of one-repetition maximum appears to be the threshold for meaningful osteogenic stimulus. However, a 2020 meta-analysis found comparable bone mineral density outcomes at lower loads when effort was adequate (Grgic et al., 2020). The stimulus must exceed habitual demand, whether through load, accumulated tension, or variety of movement.
Light circuit training, resistance bands, and bodyweight programs have genuine value for other purposes. For bone health specifically, the load needs to be sufficient. For runners, that bar is higher than for sedentary individuals. Progressively increasing the challenge over time is not optional. It is the mechanism.
Frequency and Exercise Selection
Current evidence supports resistance training at least twice per week for osteogenic benefit. Exercise selection should prioritize large compound movements that load weight-bearing skeletal sites: squats, deadlifts, hip hinges, loaded carries, and overhead pressing. These engage large muscle groups and direct significant mechanical loading to the bones most commonly affected by low bone mineral density in endurance athletes.
Time
Bone mineral density changes are slow. Research consistently points to 7 to 9 months of sustained training before changes become measurable on a DEXA scan. Short programs may drive changes in bone turnover markers, but structural changes in density require sustained loading over a longer window. Starting a strength program for bone health and expecting to see results in 8 weeks is a mismatch between expectation and biology.
Energy Availability
Bone cannot adapt in an energy-deficient environment. This is the central finding of the RED-S (Relative Energy Deficiency in Sport) framework, and it applies directly here. Blagrove et al. (2024) addressed this explicitly in the context of resistance training and return to performance after RED-S: energy needs must be met before the skeleton can respond to training load, no matter how well-structured that training is.
Endurance athletes frequently underestimate caloric needs. A runner who is lifting consistently and progressively but chronically under-fueling will likely not produce meaningful bone adaptation. The energy environment has to support the process. Fueling before and after strength sessions is not a performance detail. For bone health, it is a prerequisite.
The Complete Picture
Load: At or above 70% of 1RM, progressively increased over time
Frequency: At least twice per week
Exercise selection: Large compound movements targeting weight-bearing sites
Duration: Sustained commitment of 7 to 9 months minimum before measurable change
Energy availability: Adequate fueling as a non-negotiable prerequisite
Most runner-focused strength programs are not designed with these parameters in mind. They are designed for injury prevention, performance, or general conditioning. Those are legitimate goals. But if bone health is the clinical priority, the programming needs to reflect the specific demands of skeletal adaptation.
The Through-Line
Bones need more than running. Pregnancy needs more than rest. Parameters need more than good intentions. The body adapts to the demands placed on it, provided those demands are novel enough, sufficient enough, and sustained enough, in an energy environment that supports the adaptation. That is the whole framework.
Build the capacity. Let the adaptation follow.
Frequently Asked Questions
Is running bad for bone health?
No. Running provides a genuine bone-loading stimulus, particularly in early training. The problem is habituation: bone cells become less responsive to repetitive loading over time, and the osteogenic response plateaus after relatively few loading cycles per session. Running is beneficial for bone health, especially when combined with progressive resistance training.
How heavy do I need to lift to improve bone density?
Research suggests loading at or above 70 percent of your one-repetition maximum is associated with meaningful osteogenic stimulus, though lower loads can produce comparable outcomes when effort is adequate. The exact approach should be progressive and individualized based on training history, current capacity, and any specific bone density concerns.
How long does it take to see changes in bone mineral density from strength training?
Research consistently points to 7 to 9 months of sustained training before changes become measurable on a DEXA scan. Consistency is the variable most within your control.
Is lifting weights safe during pregnancy?
For most women with uncomplicated pregnancies, the current evidence supports resistance training throughout pregnancy. A 2025 systematic review found that women who lifted during pregnancy had lower rates of gestational diabetes, preeclampsia, and mood disorders, with no increased fetal risk. Women with high-risk pregnancies or specific contraindications should consult their obstetric team.
What exercises are best for bone health in runners?
Heavy compound movements that load weight-bearing skeletal sites are most effective: squats, deadlifts, hip hinges, loaded carries, and step-ups. Upper body compound movements like overhead pressing and rows address sites not as heavily loaded by running.
Can I improve bone density if I have been diagnosed with osteopenia or a stress fracture history?
Yes. Progressive resistance training is one of the most evidence-supported interventions for improving bone mineral density. Programming needs to account for your specific history, the skeletal sites of concern, and your current training status. Working with a physical therapist who understands both bone health and performance training is worth the investment.
Does fueling affect bone adaptation?
Yes, significantly. Bone cannot adapt in an energy-deficient environment. Chronic low energy availability directly suppresses bone formation regardless of training load. Adequate fueling before and after sessions is a prerequisite for the adaptation to occur.
Do I need a physical therapist to start a bone health strength program?
Not necessarily to start, but a physical therapist can help you design a program that accounts for your specific bone density status, training history, injury history, and running load. For runners with a history of stress fractures, low bone density, or RED-S, individualized guidance is worth it.
Where is Zero Point One Physical Therapy located?
We are located at 18 West 27th Street, 4th Floor, New York, NY 10001, in the NoMad and Flatiron District of Manhattan. Two blocks from the 28th Street subway stations (N, R, W, and 6 trains) and walking distance from Madison Square Park, Chelsea, Gramercy, and Midtown.
Do you work with runners in New York City on bone health and strength training?
Yes. Runners are one of our primary populations. Whether you are training for a marathon, dealing with a stress reaction history, or simply want a strength program designed around how your skeleton actually adapts, we offer 1-on-1 sessions with a Doctor of Physical Therapy who specializes in performance and load management. Sessions are 60 to 90 minutes, fully individualized, and built around your training goals.
Work With Us
Zero Point One Physical Therapy is located in the heart of NoMad and the Flatiron District in Manhattan. We work 1-on-1 with runners, athletes, and active adults who want to train harder, recover smarter, and build a body that holds up over time.
If bone health, strength training, or prenatal fitness is something you are navigating, we would love to help you build a plan that is specific to you.
Zero Point One Physical Therapy
18 West 27th Street, 4th Floor
New York, NY 10001
NoMad / Flatiron District, Manhattan
Two blocks from the 28th Street subway stations (N, R, W, 6 trains). Walking distance from Madison Square Park, Midtown, Chelsea, and Gramercy.
References
Blagrove, R.C., Brooke-Wavell, K., Plateau, C.R., Nahman, C., Hassan, A., and Stellingwerff, T. (2024). The role of musculoskeletal training during return to performance following relative energy deficiency in sport. International Journal of Sports Physiology and Performance, 19(7), 623-628.
Fuchs, R.K., Bauer, J.J., and Snow, C.M. (2001). Jumping improves hip and lumbar spine bone mass in prepubescent children: a randomized controlled trial. Journal of Bone and Mineral Research, 16(1), 148-156.
Grgic, J., Garofolini, A., Orazem, J., Sabol, F., Schoenfeld, B.J., and Pedisic, Z. (2020). High versus low-load resistance training on bone mineral density and content in middle-aged and older people: a systematic review with meta-analysis. Maturitas.
Hart, N.H., Nimphius, S., Rantalainen, T., Ireland, A., Siafarikas, A., and Newton, R.U. (2017). Mechanical basis of bone strength: influence of bone material, bone structure and muscle action. Journal of Musculoskeletal and Neuronal Interaction, 17(3), 114-139.
Hong, A.R., and Kim, S.W. (2018). Effects of resistance exercise on bone health. Endocrinology and Metabolism (Seoul), 33(4), 435-444.
Piasecki, J., Ireland, A., Piasecki, M., Deere, K., Hannam, K., Tobias, J.H., and McPhee, J.S. (2018). Hip and spine bone mineral density are greater in master sprinters, but not endurance runners compared with non-athletic controls. Bone.
Prevett, C., Kimber, M., Morin, M., and Cyr, M. (2023). Heavy resistance training during pregnancy: maternal and neonatal outcomes. International Urogynecology Journal.
Prevett, C., Moore, I.S., and Goom, T. (2025). Resistance training during pregnancy: a systematic review and meta-analysis. British Journal of Sports Medicine.
Rubin, C.T., and Lanyon, L.E. (1984). Regulation of bone formation by applied dynamic loads. Journal of Bone and Joint Surgery, 66(3), 397-402.
Scofield, K.L., and Hecht, S. (2012). Bone health in endurance athletes: runners, cyclists, and swimmers. Current Sports Medicine Reports, 11(6), 328-334.
Zhao, R., et al. (2025). Resistance training parameters for improving bone health. [Cited in context of Blagrove et al., 2024 review framework.]
Zero Point One Physical Therapy | 18 W 27th Street, 4th Floor, New York, NY 10001 | Evidence-Informed. Performance-Forward.
Serving runners, athletes, and active individuals in NoMad, Flatiron, Midtown, Chelsea, Gramercy, and across New York City.