Parameters of Exercise to Prevent Osteoporosis
Condition: Osteoporosis, Postmenopausal
MeSH terms: Osteoporosis; Osteoporosis, Postmenopausal
Study type: Interventional

Summary: 
      The principal goal of this study is to determine parameters of walking in terms of peak
      mechanical vertical force, bout duration, and bout spacing that can preserve or increase bone
      mineral density (BMD) in postmenopausal women. Release of pulses of parathyroid hormone
      (PTH), growth hormone (GH), and of markers of bone resorption and bone formation will be used
      as indicators of the osteogenic effects of a short exposure to exercise. When secreted in
      pulsatile fashion, GH stimulates osteoblast proliferation, particularly in cortical bone (27,
      28). Like GH, the pattern of PTH secretion determines the nature of its effect on bone. When
      it is secreted in pulsatile manner, PTH contributes to bone formation through activation of
      bone lining cells, differentiation of osteoprogenitor cells, and suppression of bone cell
      apoptosis .
    

Detailed description: 
      A. Hypotheses and specific aims:

      Specific aim 1. Measure plasma concentrations of anabolic hormones (parathyroid hormone (PTH)
      and growth hormone (GH), at sufficient frequency to define the area under the curve (AUC),
      and of markers of bone formation (osteocalcin, carboxyterminal propeptide of type 1
      procollagen (CICP), and bone-specific alkaline phosphatase (ALKP)), and markers of bone
      resorption (immunoreactive carboxyterminal telopeptide of type I collagen (CTX)) after
      40-minutes of treadmill exercise at the relative intensity of 125% of the ventilatory
      threshold (VT) corresponding to about 1.78 m/sec (4 miles/h), and two intensities of
      mechanical loading (724, and 1411 N), in healthy postmenopausal women.

      Hypothesis 1. Bone formation, as assessed by increases in markers of bone formation and
      decreases in markers of bone resorption, will be higher in response to dynamic exercise at a
      level of mechanical loading that produces increased secretion of PTH and GH than to exercise
      at other loading intensities.

      Specific aim 2. Measure plasma concentrations of anabolic hormones), at sufficient frequency
      to define the area under the curve (AUC), and of markers of bone formation as in specific aim
      1, after two 20-minutes of treadmill exercise, separated by 7 h, at the relative intensity of
      125% of the ventilatory threshold (VT) corresponding to about 1.78 m/sec (4 mi/h), and two
      intensities of mechanical loading (724, and 1411 N), in healthy postmenopausal women.

      Hypothesis 2. A 7-hour interval separating the two bouts of exercise will have greater bone
      anabolic effect than the equivalent volume and intensity of exercise performed in a single
      bout.
    

Intervention name(s): Experimental: 40 minute up trial; Experimental: 40 minute down trial; Experimental: Two 20 minute up trials; Experimental: Two 20 min down trials; Active Comparator: Sedentary trial
Intervention type(s): Behavioral; Behavioral; Behavioral; Behavioral; Behavioral
Other intervention name(s): 40 minutes of uphill exercise divided into two 20-minute trials separated by 7 h; 40 minutes of downhill exercise divided into two 20-minute trials separated by 7 h; 40 minutes of uphill exercise separated in two 20-min bouts 7 h apart; 40 minutes of uphill exercise separated in two 20-min bouts 7 h apart; A control no-exercise trial
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Intervention model description: Five parallel groups, matched for age and BMI, where exercise was applied at 6o uphill or 6o downhill either as one 40-min morning bout or as two 20-min half bouts distributed 7 h apart. A sedentary group served as a control for the four exercise groups.
Masking: None (Open Label)
Primary purpose: Basic Science