Relationships between self-reported lifetime physical activity, estimates of current physical fitness, and aBMD in adult premenopausal women.

Osteoporosis is common, and physical activity is important in its prevention and treatment. Of the categories of historical physical activity (PA) examined, we found that weight-bearing and very hard physical activity had the strongest relationships with areal bone mineral density (aBMD) throughout growth and into adulthood, while for measures of strength, only grip strength proved to be an independent predictor of aBMD. PURPOSE/INTRODUCTION: To examine relationships between aBMD (total body, lumbar spine, proximal femur, tibial shaft, distal radius) and estimates of historical PA, current strength, and cardiovascular fitness in adult premenopausal women. METHODS: One hundred fifty-two adult premenopausal women (40 ± 9.6 years) undertook aBMD (dual-energy X-ray absorptiometry (DXA)) and completed surveys to estimate historical physical activity representative of three decades (Kriska et al. [1]), while subsets underwent functional tests of isokinetic strength (hamstrings and quadriceps), grip strength (hand dynamometer), and maximum oxygen uptake (MaxV02; cycle ergometer). Historical PA was characterized by demand (metabolic equivalents, PA > 3 METS; PA > 7 METS) and type (weight-bearing; high impact). RESULTS: Significant positive independent predictors varied by decade and site, with weight-bearing exercise and PA > 3 METS significant for the tibial shaft (10-19 decade) and only PA > 7 METS significant for the final two decades (20-29 and 30-39 years; total body and total hip). A significant negative correlation between high impact activity and tibial shaft aBMD appeared for the final decade. For strength measures, only grip strength was an independent predictor (total body, total hip), while MaxV02 provided a significant independent prediction for the tibial shaft. CONCLUSIONS: Past PA > 7 METS was positively associated with aBMD, and such activity should probably constitute a relatively high proportion of all weekly PA to positively affect aBMD. The findings warrant more detailed investigations in a prospective study, specifically also investigating the potentially negative effects of high impact PA on tibial aBMD.

Impact exercise and bone density in premenopausal women with below average bone density for age.

PURPOSE: To study the effects of two home-based impact exercise programs on areal bone mineral density (aBMD) in adult premenopausal women with below average aBMD for age (negative Z-scores; 40.8 years; n = 107). METHODS: Two unilateral impact exercise programs were employed, one targeting the total hip and lumbar spine (n = 42 pairs), the other the distal radius (n = 24 pairs) with some individuals performing both. Force plate data were used to establish exercise loading characteristics (peak loads, time to peak), dual-energy X-ray absorptiometry (DXA) provided bone data. Calcium intake, health and extraneous physical activity (PA) were determined by survey. Exercise for both hip and spine consisted of unilateral landings from adjustable steps (maximum height 63.5 cm) while impacts were delivered to the forearm by arresting falls against a wall. An exercise log was used to provide the exercise prescription, record each exercise bout and any injuries. Participants were randomly assigned to exercise or control groups and pair-matched (age, BMI, Z-score, aBMD). Compliance was calculated as the number of sessions completed divided by the total prescribed number (mean ~50 %). RESULTS: The programs delivered significant gains pre to post at each site compared with significant losses in controls (forearm: 3.9 vs -3.9 %; total hip: 2.0 vs -2.6 %; lumbar spine: 2.8 vs -2.9 % exercise and controls, respectively, all p < 0.001). No exerciser lost bone at the target site regardless of compliance which was strongly correlated with bone gains (R (2) = 0.53-0.68, all p < 0.001). CONCLUSIONS: Impact exercise provides an effective means of improving below average aBMD without supervision in this at risk population.

Muscle activation patterns in the scapular positioning muscles during loaded scapular plane elevation: the effects of Latent Myofascial Trigger Points.

BACKGROUND: Latent Myofascial Trigger Points are pain-free neuromuscular lesions that have been found to affect muscle activation patterns in the unloaded state. The aim was to extend these observations to loaded motion by investigating muscle activation patterns in upward scapular rotator muscles (upper and lower trapezius and serratus anterior) hosting Latent Myofascial Trigger Points simultaneously with lesion-free synergists for shoulder abduction (infraspinatus and middle deltoid). This approach allowed examination of the effects of these lesions on both their hosts and their lesion-free synergists in order to understand their effects on the performance of shoulder abduction. METHODS: Surface electromyography was employed to measure the timing of onset of muscle activation of the upper and lower trapezius and serratus anterior (upward scapular rotators), infraspinatus (rotator cuff) and middle deltoid (abductor of the arm) initially without load and then with light (1-4 kg) dumbbells. Comparisons were made between control (no Latent Trigger Points; n=14) and Latent Trigger Point (n=28) groups. FINDINGS: The control group displayed a relatively stable sequence of muscle activation that was significantly different in timing and variability to that of the Latent Trigger Point group in all muscles except middle deltoid (all P<0.05). The Latent Trigger Point group muscle activation pattern under load was inconsistent, with the only common feature being the early activation of the infraspinatus. INTERPRETATION: The presence of Latent Trigger Points in upward scapular rotators alters the muscle activation pattern during scapular plane elevation, potentially predisposing to overuse conditions including impingement syndrome, rotator cuff pathology and myofascial pain.