High-impact exercise boosts bone density without harming knee health in postmenopausal women

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Jul 2 2024

In a recent study published in the Journal of Bone and Mineral Research, researchers assessed the impact of high-impact exercise on femoral neck bone density and knee osteoarthritis (OA) (a degenerative joint disease causing cartilage breakdown and joint pain) imaging biomarkers in healthy postmenopausal (the period in a woman's life after her menstrual cycles have ceased for twelve consecutive months) women.

Study: High-Impact Exercise Increased Femoral Neck Bone Density With No Adverse Effects on Imaging Markers of Knee Osteoarthritis in Postmenopausal Women. Image Credit: lzf / Shutterstock

Background 

Osteoporosis (OP) (a condition characterized by weakened bones, increasing the risk of fractures) and OA affect millions globally, with higher bone mineral density (BMD) linked to decreased OA progression risk but increased knee OA risk. Postmenopausal women are at higher OP risk due to estrogen deficiency and have a higher OA prevalence than men. High-impact exercise can increase BMD, with mixed results in postmenopausal women. Progressive unilateral exercise has improved femoral neck BMD in premenopausal women and older men. Further research is needed to confirm the long-term effects and safety of high-impact exercise on bone and joint health in postmenopausal women.

About the study 

The present trial involved 6 months of high-impact unilateral exercise on a randomly assigned exercise leg (EL) compared to the contralateral control leg (CL). Approved by ethics committees, participants provided written informed consent before enrollment. Postmenopausal women aged 55 to 70 years were recruited, with exclusions for OP pharmaceutical treatment eligibility, joint injuries, medical conditions precluding exercise, body mass index (BMI) over 30 kg/m², recent ionizing radiation studies, high-impact exercise frequency, Magnetic Resonance Imaging (MRI) or Dual-energy X-ray Absorptiometry (DXA) contraindications and bone-affecting medications.

Screening included telephone interviews and baseline testing, covering health and physical activity questionnaires, DXA scans, and eligibility assessments. Baseline MRI scans and Ground Reaction Force (GRF) data collection followed familiarization with the hopping protocol. Participants were randomly assigned an exercise leg and completed the first supervised session. After 6 months, repeat DXA, MRI, and force plate data were collected.

Health data, physical activity, and calcium intake were recorded. DXA scans analyzed whole-body, femurs, and lumbar spine for femoral neck BMD, bone mineral content (BMC), and section modulus (Z). Semiquantitative scoring for bone marrow lesions (BML) and cartilage defects used the MRI Osteoarthritis Knee Score (MOAKS) system. GRFs during hopping estimated osteogenic load.

The intervention required 50 daily multidirectional hops, progressing over 6 months, with participants maintaining exercise diaries. Data analysis employed paired t-tests, repeated measures Analysis of Variance (ANOVA), and McNemar tests, with significance set at p < 0.05. Sample size calculations required 30 participants to detect femoral neck BMD changes.

Here's a wild study! Researchers randomly assigned aging women to *jump on one leg* 50 times for 6 months to see if it would increase bone density compared to the non-jumping leg. It worked! https://t.co/kYy0LJh7Wj pic.twitter.com/ccwFMgotxh

— Thomas Talhelm (@ThomasTalhelm) July 1, 2024

Study results 

Baseline characteristics indicated no significant differences in femoral neck T-scores between the legs. Among the 42 participants randomized, follow-up data were available for 35. Seven participants were lost to follow-up or withdrew due to knee discomfort or Achilles tendinopathy. Two participants formally withdrew but returned for follow-up data; one withdrew due to knee discomfort, which recovered after stopping the exercise, and another due to a non-intervention-related knee injury.

Adherence was assessed during the final 16 weeks when participants were prescribed 50 hops daily. The mean adherence was 76.8%, with 29 participants exercising at least 4 days per week. Participants reported an average of 3.4 days of missed sessions, mostly due to ankle or knee soreness.

There were no significant changes in total body fat mass, lean mass, or lean mass of the EL and CL. The mean peak vertical (v)GRFs of 10 consecutive hops showed no difference between the legs at baseline. Post-intervention, vGRF increased in both legs (EL by 10% and CL by 7%), indicating increased hopping intensity over 6 months.

Bone measurements indicated no baseline differences between legs. After 6 months of high-impact exercise, mean femoral neck BMD increased in the EL by 0.81% and decreased in the CL by 0.57%. Similar changes were observed for BMC and Z. BMD decreased by 0.9% from baseline.

In individual regions of interest (ROIs), the medial tibial ROI of the central slice showed a significant leg × time interaction, which was not statistically significant after adjusting for multiple comparisons.

Semiquantitative assessment of knee joint measures showed high baseline prevalence of BMLs and cartilage defects, particularly in the patellofemoral joint (PFJ). Following the intervention, there were no significant differences between ROIs that progressed and those that did not. Five participants had BML progression in the EL and five in the CL. Four participants had BML score improvements in the EL and five in the CL. Six participants had progression of cartilage defects in the EL and four in the CL, with two improvements in the EL and three in the CL.

Conclusions 

To summarize, this study is the first to show that six months of high-impact, unilateral exercise can significantly improve femoral neck BMD, BMC, and Z in postmenopausal women without negatively affecting knee cartilage or OA progression. These findings contrast with previous meta-analyses and suggest that regular, progressive loading effectively enhances bone strength in this population. The study also indicated that high-impact exercise is a safe and beneficial intervention for improving hip strength in postmenopausal women.