Christine M. Snow
Kerri M. Winters-Stone and Christine M. Snow
We conducted a double-blind, placebo-controlled, randomized trial to determine whether 1 year of supplemental calcium intake would augment hip [greater trochanter, GT, femoral neck (FN), total hip (TH)], spine (LS), and femoral mid-shaft (Fmr) BMD in female distance runners. Twenty-three women (age: 23.7 ± 4.7 yrs, height: 165.6 ± 6.3 cm, weight: 55.7 ± 6.1 kg) were randomly assigned to receive either 1000 mg/d of supplemental calcium (N = 13) or placebo tablets (N = 10) for 1 year. BMD was determined by DXA (Hologic 1000-W) and tablet compliance by self-report logs. Compliance averaged 79% and 71% for supplement and placebo groups, respectively. Calcium supplementation did not affect hip or spine BMD, but did prevent loss at the femoral mid-shaft (GT: –0.5% vs. 0.2%, FN: 0.9% vs. 1.1%, TH: –0.3% vs. 0.2%, LS: 0.3% vs. 1.2%, Fmr: 0.1% vs. –1.8%, for calcium vs. placebo, respectively). We conclude that the addition of 800 mg/d of supplemental calcium to the diet of young adult female distance runners with habitual calcium intakes of ~1000 mg/d, prevents cortical but not trabecular bone loss.
Karen N. White, Katherine B. Gunter, Christine M. Snow and Wilson C. Hayes
The Quick Step measures reaction time and lateral stepping velocity. Upon a visual cue, participants step to the side as quickly as possible. Instrumentation includes floor pads with pressure-sensitive switches and two timers. In all, 109 older adults who had experienced a recent fall, 46 older adult nonfallers, and 24 young adults volunteered for testing. Reliability for reaction time and stepping velocity was good to excellent (intraclass correlation = 0.69–0.85). Multivariate analysis of variance revealed a significant difference between groups, p < 0.01, but not between stepping directions, p = 0.62–0.72, for both reaction time and stepping velocity. Reaction times were different among the three groups, p < 0.01, with the young adults having the fastest times and the older adult fallers having the slowest times. Lateral stepping velocity was faster among the young adults than for the two older groups, p < 0.01, but did not differ between the older adults, p = 0.29. It is concluded that the Quick Step is a simple and reliable tool for determining reaction time and lateral stepping velocity, and that this test can be used to detect a significant difference in reaction time between older adult fallers and nonfallers.
Jeremy J. Bauer, Robyn K. Fuchs, Gerald A. Smith and Christine M. Snow
Drop landings increase hip bone mass in children. However, force characteristics from these landings have not been studied. We evaluated ground and hip joint reaction forces, average loading rates, and changes across multiple trials from drop landings associated with osteogenesis in children. Thirteen prepubescent children who had previously participated in a bone loading program volunteered for testing. They performed 100 drop landings onto a force plate. Ground reaction forces (GRF) and two-dimensional kinematic data were recorded. Hip joint reaction forces were calculated using inverse dynamics. Maximum GRF were 8.5 ± 2.2 body weight (BW). At initial contact, GRF were 5.6 ± 1.4 BW while hip joint reactions were 4.7 ± 1.4 BW. Average loading rates for GRF were 472 ± 168 BW/s. Ground reaction forces did not change significantly across trials for the group. However, 5 individuals showed changes in max GRF across trials. Our data indicate that GRF are attenuated 19% to the hip at the first impact peak and 49% at the second impact peak. Given the skeletal response from the drop landing protocol and our analysis of the associated force magnitudes and average loading rates, we now have a data point on the response surface for future study of various combinations of force, rate, and number of load repetitions for increasing bone in children.
Katherine B. Gunter, Jennifer De Costa, Karen N. White, Karen Hooker, Wilson C. Hayes and Christine M. Snow
This study assessed changes in balance self-efficacy (BSE) over 1 year in community-dwelling elderly, compared changes in BSE between fallers and nonfallers, and assessed the relationship between specific balance and mobility risk factors for side falls and BSE scores. Elderly fallers (n = 67; 80.2 ± 5.9 years) and nonfallers (n = 75; 79.4 ± 4.9), categorized based on self-reported falls over 1 year, were tested at baseline on postural sway, hip-abduction strength, lateral-stepping velocity, tandem walk, and get-up-and-go and given a BSE questionnaire. Fallers had lower BSE scores than nonfallers did (141.6 ± 33.5 and 154.9 ± 25.4; p = .008). BSE did not change over 1 year. In stepwise regression, BSE scores were predictive of time on the get-up-and-go, mediolateral sway, and tandem walk independent of age, height, and strength (p < .001). The BSE scale might be useful for screening individuals at risk for injurious falls because it is inexpensive and noninvasive.