Title page for ETD etd-05252001-151500


Type of Document Dissertation
Author Wootten, David F
Author's Email Address dwootten@vt.edu
URN etd-05252001-151500
Title Short Term Time Course Skeletal Responses to High Intensity Physical Exercise
Degree PhD
Department Human Nutrition, Foods, and Exercise
Advisory Committee
Advisor Name Title
Herbert, William G. Committee Chair
Bos, Ronald R. Committee Member
Cross, Lawrence H. Committee Member
Nickols-Richardson, Sharon M. Committee Member
Ramp, Warren K. Committee Member
Keywords
  • biochemical markers of bone turnover
  • mechanical response tissue analysis
  • bone mineral density
  • exercise
Date of Defense 2001-04-27
Availability unrestricted
Abstract
The purpose of this randomized controlled trial was to investigate temporal skeletal responses to short-term high intensity physical activity. Twenty-eight normal active females [age: 20.7 +/- 2.1 yr (mean +/- SD)] were randomized into exercise (EX, n = 15) or control (CN, n = 13) groups. The exercise group trained 6 days/wk for 6 wk, which consisted of maximal isokinetic knee flexion/extension 3 days/wk, combined with 3 days/wk running. The purpose was to expose the tibiae to a period of abruptly increased loading forces. Tibial bending stiffness (EIMRTA), and serum concentrations of biochemical markers of bone formation [osteocalcin (OC)], and bone resorption [n-telopeptide of type I collagen (NTx)] were measured at baseline, 2 wks, 4 wks, and 6 wks. Isokinetic concentric knee extension/flexion peak torque, as well as total body and site-specific bone mineral density (BMD) were measured at baseline and 6 wk. After training, the exercise group significantly increased (p < 0.05) isokinetic concentric peak torque for the dominant (13.6%) and non-dominant (5.7%) quadriceps, as well as dominant (7.7%) and non-dominant (9.5%) hamstrings, compared to the controls. No differences for total body or site-specific BMD were noted. A two-way multivariate repeated measures ANOVA revealed no time•group interactions for composite tibial bending stiffness [(EIMRTA); p = 0.57] or the biochemical markers of bone turnover [(OC and NTx); p = 0.15] across the four sampling periods. While there were no main effects for group, a trend for time (p = 0.051) for composite EIMRTA was observed. The exercise group demonstrated a 20% increase in EIMRTA from baseline (74.8 +/- 22.3 Nm2) to 6 wk (89.8 +/- 24 Nm2), compared to controls who demonstrated a 4% increase (Baseline 86.5 +/- 23.8 Nm2; 6 wk 90 +/- 23.7 Nm2). Significant group differences (p = 0.05) were noted for OC, but not NTx. Differences (p < 0.05) for OC were observed at baseline [13.2 +/- 2.4 ng/ml (CN), 15.6 +/- 2.7 ng/ml (EX)], and follow-up ANCOVA revealed no differences for subsequent sampling periods. Main effects for time were found for OC and NTx (p < 0.001). Main effects for time in OC were attributable to changes in the exercise group (p < 0.01) and NTx (p < 0.01), but not the control group.
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