The effect of high-impact exercise on imaging biomarkers of osteoporosis and osteoarthritis in postmenopausal women
2020-05-06T10:38:54Z (GMT) by
Osteoporosis and osteoarthritis are highly prevalent conditions that result in high levels of disability and healthcare costs. For both conditions, age and female sex are risk factors. High impact exercise interventions have improved outcome measures related to fracture risk across several age and sex cohorts, but there have been mixed findings in postmenopausal women, the group at greatest risk of osteoporosis. Despite limited evidence of exercise being a risk factor for osteoarthritis, there may be concern from older people about any potential negative effects high impact exercise may have on their joints. Imaging technologies have been well validated to analyse changes in both bone strength and joint health following interventions. The aim of this thesis was to use imaging technologies to assess changes in markers associated with osteoporosis and osteoarthritis following a high impact exercise intervention in postmenopausal women.
The first two studies in this thesis established a valid and reliable methodology for analysing joint health prior to the intervention study. First, a systematic review of studies using compositional MRI to assess changes in articular cartilage following loading was conducted. The results of the review indicated that T2 mapping was the most widely used technique and that changes in compositional MRI outcome variables were mostly localised and exercise specific, with no evidence of long-term detrimental effects of chronic loading.
Study two established the between-scan reproducibility of T2 mapping for different regions of interest in the knee. Six older women were scanned twice (one week apart) and changes in T2 relaxation times were analysed. Results showed that the reproducibility (%CVRMS) ranged from 3.74% to 14.82% with a mean of 8.68±2.70%. These figures were comparable with previous studies and confirmed the protocol for acquiring and analysing MRI scans during the intervention study.
In study three, forty-two women were recruited to a unilateral, high impact exercise intervention lasting six months. Participants completed a progressive hopping exercise on a randomly assigned exercise leg, which was compared to the contralateral control leg. Dual X-ray absorptiometry (DXA) scans were acquired before and after the intervention, to assess changes in femoral neck bone mineral density, content and section modulus. Magnetic resonance imaging (MRI) of the knee joint was conducted before and after the intervention to provide information on the biochemical composition of the cartilage using T2 relaxometry, and semi-quantitative analysis of further joint pathology. Unilateral static postural sway was measured using a force plate before and after the intervention. Thirty-five participants completed the intervention with a mean adherence of 76.822.5%. Femoral neck bone mineral density, bone mineral content and section modulus all increased in the exercise leg (+0.81%, +0.69% and +3.18% respectively), compared to decreases in the control leg (-0.57%, -0.71% and -0.75%: all interaction effects P<0.05). There was a significant increase in mean T2 relaxation times (main effect of time P=0.011), but this did not differ between the exercise leg and control leg, indicating no global effect. The semi-quantitative analysis showed a high prevalence of bone marrow lesions and cartilage defects, especially in the patellofemoral joint, with no indication that the intervention caused pathology progression. Improvements in unilateral postural sway speed and mediolateral sway path were seen in both legs and not affected by the intervention.
Study four investigated a range of weight-bearing movements to provide the ground reaction forces produced, and the osteogenic potential of these exercises. Twenty-eight older women were recruited and asked to perform multiple repetitions of fourteen different activities on a force plate. The maximum ground reaction force recorded for each movement was compared. Results indicated that stamps and skipping may be good candidates for exercises to increase femoral neck bone mineral density.
This research is the first to demonstrate that a unilateral, high impact exercise intervention—that is simple, free and home-based—can improve femoral neck bone mineral density in healthy postmenopausal women. The results from both compositional and semi-quantitative MRI, used for the first time during a high impact intervention, there was no evidence of detrimental changes in knee joint health. Unilateral, multidirectional hopping appears to be a feasible, safe an effective intervention to reduce fracture risk in healthy, postmenopausal women