Bone remodeling as a response to exercise in human subjects is described in the literature, although most studies treat exercise as a qualitative factor contributing to bone remodeling. Quantitative description requires assessment of the mechanical loads on the bones. This work describes a generalized lower extremity model that uses existing musculoskeletal modeling techniques to quantify mechanical variables in the femoral neck during exercise. An endurance exercise program consisting of walking, jogging jumping rope, and weight-training was analyzed. Peak femoral neck cortex stresses and strains were high during jogging and squatting, compared to walking, whereas jumping rope and other weight-training exercises produced peak stresses comparable to or lower than walking. Peak stress and strain rates were significantly higher for walking, jumping rope, and jogging than for weight-training. The model should prove useful for any study investigating a quantitative relationship between exercise and bone remodeling.
David D. Anderson, Ben M. Hillberry, Dorothy Teegarden, William R. Proulx, Connie M. Weaver and Tomoaki Yoshikawa
Marianne S. Eagan, Roseann M. Lyle, George P. McCabe and Dorothy Teegarden
Assessing past activity in study populations is important in health-related research. This study examined intrasubject stability of a comprehensive, self-administered Historical Activity Questionnaire (HAQ) developed for women, age 18 to 30 y, participating in a larger (N = 153) intervention.
Volunteers (n = 31) completed the HAQ at baseline and 6.5 months. Activity, (h/d) and metabolic equivalent (MET)-h/d, was divided into elementary, middle, high school, occupation, athletics, leisure, and exercise impact levels and loading.
(MET-h/d) cumulative, past activity test–retest was r = 0.76. Highest stability was in total athletic participation (r = 0.82), and impact 3 (r = 0.87). Loading test–retest was r = 0.51.
The HAQ provides a moderately stable, user-friendly instrument for documenting past activity in young women, particularly for past athletic and high-impact activity recall. The addition of impact and loading activity makes this questionnaire unique, and provides a model for inclusion of these components in other activity questionnaires.
Kimberly M. White, Roseann M. Lyle, Michael G. Flynn, Dorothy Teegarden and Shawn S. Donkin
The purpose of this study was to test the effect of acute dairy calcium intake on exercise energy metabolism and endurance performance. Trained female runners completed two trials. Each trial consisted of a 90-min glycogen depletion run followed by a self-paced 10K time trial, conducted one hour after consumption of a high dairy (500 mg Ca+2) or low dairy (80 mg Ca+2) meal. During the 90-min run, blood samples and respiratory gases were collected. No treatment main effects of acute dairy intake were found for respiratory exchange ratio (RER), calculated fat oxidation, lactate, glycerol, or 10K time. Following this protocol, acute dairy calcium intake did not alter fat utilization or endurance performance in trained female runners.