Dose‐response effects of exercise on bone mineral density and content in post‐menopausal women

Exercise is one of the most widely used non‐pharmacological strategies to prevent bone resorption during menopause. Given the detrimental consequences of bone demineralization, the purpose of this study was to examine the effects of prescribing different exercise volumes on bone mineral density and content in previously inactive, post‐menopausal women during a 12‐month intervention and 1 year after intervention completion. Four hundred post‐menopausal women were randomized to either 150 min/wk (MODERATE dose group) or 300 min/wk (HIGH dose group) of aerobic exercise. Total bone mineral density (g/cm²) and bone mineral content (g) were assessed at baseline, 12 months (end of the intervention) and 24 months (follow‐up) using whole body dual‐energy X‐ray absorptiometry. At 12 months, mean bone mineral density among women in the HIGH dose group was estimated to be 0.006 g/cm² (95% CI: 0.001‐0.010; P = 0.02) higher than that of women randomized to the MODERATE dose group. At 24 months, the mean difference between groups remained statistically significant, indicating higher mean bone mineral density among women in the HIGH dose group (0.007 g/cm²; 0.001‐0.001; P = 0.04). No significant differences between groups were found at any time point for bone mineral content. In an exploratory analysis, women who completed more min/wk of impact exercises had significantly higher mean levels of bone mineral density at 12 months compared to baseline (0.006 g/cm², 95% CI: 0.006‐0.012; P = 0.03). These findings suggest that higher volumes of exercise, especially impact exercise, lead to a smaller decline in total bone mineral density, which may remain following intervention completion.     

Effect of block‐periodized exercise training on bone and coronary heart disease risk factors in early post‐menopausal women: a randomized controlled study

The purpose of this 12 month randomized exercise intervention was to determine the effect of a block‐periodized multipurpose exercise program on bone mineral density (BMD) and parameters of the metabolic syndrome (MetS) in early post‐menopausal women. Eighty‐five subjects (52.3 ± 2.4 years) living in the area of Erlangen (Germany) were randomly assigned into an exercise (EG, n=43) or a wellness‐control group (CG: n=42). The EG performed a periodized multipurpose exercise program with 4–6‐week blocks of high‐intensity bone‐specific exercise intermitted by 10–12 weeks of exercise dedicated to increase endurance and reduce cardiac and metabolic risk factors. The CG performed a low‐volume/low‐intensity “wellness” program to increase well‐being. After 12 months, significant exercise effects were observed for the lumbar spine (LS) BMD as assessed by quantitative computed tomography [total BMD (EG: ?0.3 ± 2.1% vs CG: ?2.1 ± 2.2%, P=0.015); trabecular BMD (EG: ?0.7 ± 3.4% vs CG: ?4.7 ± 4.9%, P=0.001) and dual‐energy x‐ray absorptiometry (DXA) (EG: ?0.1 ± 2.2% vs CG: ?2.0 ± 2.0%, P=0.002)]. However, no significant effects were observed for total hip BMD as assessed by DXA (P=0.152). Although all MetS parameters were favorably affected among the EG, only the effect for waist circumference was significant. In summary, short periods of bone‐specific intervention embedded in longer periods of exercises dedicated to improve cardiovascular and metabolic risk factors positively affected BMD at the LS.     

Physical activity reduces bone loss in the distal forearm in post‐menopausal women – a 25‐year prospective study

Intervention studies have shown that high‐intensity training programs with duration of 1–3 years can influence bone mass in post‐menopausal women. We wanted to investigate whether moderate physical activity could be associated with reduced post‐menopausal bone loss also in the long‐term perspective. We evaluated changes in bone mass and bone structure by repeated single‐photon absorptiometry measurements of the distal forearm in 91 moderately physically active and 21 inactive women, categorized according to information from questionnaires, from menopause and on average 25 years onwards. Data were calculated with analysis of variance and analysis of covariance tests and presented as means with 95% confidence interval. There were no group differences in bone mass or bone structure at menopause. The mean annual loss in bone mineral content was 1.2% (1.1, 1.3) in the physically active and 1.6% (1.3, 1.8) in the inactive women (after adjustment for menopausal age P = 0.02) and the mean decline in a strength index based on bone mass and bone structure was 0.7% (0.6, 0.8) in the physically active and 1.2% (0.8, 1.5) in the inactive women (P = 0.004). There were no group differences in the changes in bone structure. Physical activity is also in a long‐term perspective associated with reduced post‐menopausal bone loss.     

Differential effects of strength versus power training on bone mineral density in postmenopausal women: a 2-year longitudinal study

Objectives

To investigate the effect of two different schemes of loading in resistance training on bone mineral density (BMD) and pain in pretrained postmenopausal women.

Methods

53 pretrained women (mean (SD) age 58.2 (3.7) years) who carried out a mixed resistance and gymnastics programme were randomly assigned to a strength training (ST) or power training (PT) group. The difference between the two groups was the movement velocity during the resistance training (ST, 4 s (concentric)/4 s (eccentric); PT, explosive/4 s). Otherwise both groups carried out periodised progressive resistance training (10–12 exercises, 2–4 sets, 4–12 repetitions at 70–92.5% of the one‐repetition maximum (2/week) for 2 years. Mechanical loading was determined with a force measuring plate during the leg press exercise. At baseline and after 2 years, BMD was measured at different sites with dual x‐ray absorptiometry. Pain was assessed by questionnaire.

Results

Loading magnitude, loading/unloading rate, loading amplitude and loading frequency differed significantly (p<0.001) between the two groups. After 2 years, significant between‐group differences were detected for BMD (PT, −0.3%; ST, −2.4%; p<0.05) and bone area (PT, 0.4%; ST, −0.9%; p<0.05) at the lumbar spine. At the hip, there was a non‐significant trend in favour of the PT group. Also the incidence of pain indicators at the lumbar spine was more favourable in the PT group.

Conclusion

The results show that PT may be superior for maintaining BMD in postmenopausal women. Furthermore, PT was safe as it did not lead to increased injury or pain.     

Measuring bone mineral density with fat–water MRI: comparison with computed tomography

Purpose:

To develop a method for measuring bone mineral density (BMD) with MRI, and to validate this method against quantitative computed tomography (QCT).

Materials and Methods:

A mathematical relationship between signal intensities from proton‐density‐weighted in‐phase images generated by multi‐fat‐peak T‐IDEAL MRI and BMD was derived using a set of calibration standards constructed from various concentrations of hydroxyapatite in water. Using these standards, the relationship between hydroxyapatite concentration and MRI signal intensity was examined. A T‐IDEAL protocol was performed on the patella of 5 volunteers and the signal model was used to compute BMD of all voxels of the patella. The BMD data were validated by obtaining QCT scans of the same patella, computing QCT BMD of all voxels, and comparing the MRI and QCT BMD data by performing linear regression analysis on a voxel‐by‐voxel basis.

Results:

A strong linear correlation between hydroxyapatite concentration of the calibration standards and MRI signal intensities was observed (r = 0.98; P < 0.01). In the patella, BMD measurements (N = 28796 voxels) from the MRI signal model were significantly correlated with those from QCT (r = 0.82; P < 0.001; slope = 1.02; and intercept = ?0.26).

Conclusion:

A standardized phantom consisting of hydroxyapatite and water can be used to accurately quantify BMD in vivo using MRI. J. Magn. Reson. Imaging 2013;37:237–242. © 2012 Wiley Periodicals, Inc.

     

Effects of physical exercise on bone mass,balance skill and aerobic capacity in women and men with low bone mineral density,after one year of training - a prospective study

Grahn Kronhed AC, Möller M. Effects of physical exercise on bone mass, balance skill and aerobic capacity in women and men with low bone mineral density, after one year of training - a prospective study. Vadstena is a small community in the county of östergötland, Sweden, where a project began in 1989 to prevent osteoporosis and to lower the expected incidence of osteoporotic fractures. Persons aged 40–70 years who had a low bone mineral density (BMD) value at screening of the distal radius by single-photon absorptiometry (SPA) were invited to participate in a training study during one year. The definition of low BMD was a densitometry value below ?1 SD (standard deviation) from a sex- and age-specific reference value (z-score). Fifteeen persons wanted to exercise in a group and 15 persons wanted to become a control group. All participants answered a questionnaire about lifestyle, occupation, diseases, medication and heredity. Clinical tests were made regarding mobility of the joints and muscles, balance and physical fitness. BMD for the hip and the lumbar spine were assessed by dual-energy X-ray absorptiometry (DXA) before and after the investigation period. The training programme was carried out for 60 min twice a week during one year and had the intention to improve bone mass, muscle strength and flexibility, balance skill and aerobic capacity. After the training period there was a significant increase in BMD at the greater trochanter (P<0.01), in balance skill (standing on one leg with closed eyes and “ski step“-test) (P<0.05) and in oxygen uptake capacity (P<0.05) in the exercise group. In the control group, there was a significant increase in BMD at the lumbar spine (P<0.05). However, these results should be judged with caution because several participants were over the age of 60, and at that age degenerative changes in the lumbar spine may increase to a greater or lesser extent. Regular weight-bearing exercises during one year seem to influence BMD at the greater trochanter in a training group comprising both women and men. However, our study was small in number and further training studies are needed to assess the effect of weight-bearing training on bone mass in different sex- and age-specific groups.     

Glucose response to exercise in the post‐prandial period is independent of exercise intensity

This study investigated the acute glucose response to low‐intensity, moderate‐intensity, and high‐intensity interval exercise compared to no‐exercise in healthy insufficiently active males using a four‐arm, randomized, crossover design. Ten males (age: 37.3 ± 7.3 years, BMI : 29.3 ± 6.5 kg·m⁻²) completed four 30‐minute interventions at weekly intervals comprising low‐intensity exercise (LIE ) at ~35% O₂R, moderate‐intensity exercise (MIE ) at ~50% O₂R, high‐intensity interval exercise (HIIE ) at ~80% O₂R, and a no‐exercise control. Participants performed cycle ergometer exercise 30 minutes after finishing breakfast. Glucose response was assessed using a continuous glucose monitor under free‐living conditions with dietary intake replicated. A significant effect for intensity on energy expenditure was identified (P  < .001) with similar energy cost in MIE (mean ± SD : 869 ± 148 kJ) and HIIE (806 ± 145 kJ ), which were both greater than LIE (633 ± 129 kJ). The pattern of glucose response between the interventions over time was different (P  = .02). Glucose was lower 25 minutes into each of the HIIE , MIE and LIE trials respectively (mean difference ± SD : −0.7 ± 1.1; −0.9 ± 1.1; −0.6 ± 0.9 mmol·L⁻¹; P  < .05) than in the no‐exercise trial. Glucose response was not different between exercise intensities (P  > .05). Twenty‐four‐hour AUC was not affected by exercise intensity (P  = .75). There was a significant effect for exercise enjoyment (P  = .02), with LIE (69 ± 4) preferred less than HIIE (mean ± SD : 84 ± 14; P  = .02), MIE (73 ± 5; P  = .03), and no‐exercise (75 ± 4; P  = .03). Exercise at any intensity 30 minutes after a meal affects glycemic regulation equally in insufficiently active males. Moderate to vigorous exercise intensities were preferred, and therefore, the exercise guidelines appear appropriate for the prevention of cardiometabolic disease.     

The effect of hypoxia and exercise on heart rate variability,immune response,and orthostatic stress

Hypoxia with exercise is commonly used to enhance physiological adaptation in athletes, but may prolong recovery between training bouts. To investigate this, heart rate variability (HRV), systemic immune response, and response to an orthostatic challenge were measured following exercise in hypoxia and air. Eleven trained men performed a 10‐km cycling time trial breathing hypoxia (16.5 ± 0.5% O₂) or air. HRV and the heart rate response to an orthostatic challenge were measured for 3 days before and after each trial, while venous blood samples were collected pre‐, 0, 2, and 24 h post‐exercise. Hypoxia had no significant effect compared with air. Subgroup analysis of those who had a drop in oxyhemoglobin saturation (SpO₂) > 10% between hypoxia and air compared with those who did not, demonstrated a significantly altered HRV response (△HFnu: ?2.1 ± 0.9 vs 8.6 ± 9.3, △LFnu: 2.1 ± 1.0 vs ?8.6 ± 9.4) at 24 h post‐exercise and increased circulating monocytes (1.3 ± 0.2 vs 0.8 ± 0.2 × 10⁹/L) immediately post‐hypoxic exercise. Exercise and hypoxia did not change HRV or the systemic immune response to exercise. However, those who had a greater desaturation during hypoxic exercise had an attenuate recovery 24 h post‐exercise and may be more susceptible to accumulating fatigue with subsequent training bouts.     

Walking trials in postmenopausal women: effect of low doses of exercise and exercise fractionization on coronary risk factors

We studied the fractionization of walking training and searched for the minimum dose to affect coronary risk factors in two randomized controlled trials. Altogether 134 (Study I) and 121 (Study II) healthy, sedentary postmenopausal women started the trials, and 130 (Study I) and 116 (Study II) completed them. In Study I the exercise intensity was 65% of the maximal aerobic power (VO2max) and a total of 300 kcal was expended in one (Group W1) or two (Group W2) daily walking bouts. In Study II the exercise was continuous, and the exercise intensity (% of VO2max) and energy expenditure (kcal session(-1)) were 55% and 300 kcal (Group W3), 45% and 300 kcal (Group W4), 55% and 200 kcal (Group W5) and 45% and 200 kcal (Group W6). All the subjects walked 5 days a week. The outcome measures were blood pressure, serum lipoproteins and blood glucose and plasma insulin in fasting state and also during 2-h oral glucose tolerance test in Study I. There was no change in diastolic pressure in the original study groups, but in the combined exercise group (W1+W2) in Study I, the mean diastolic pressure declined by -3.0 mmHg (95% con-fidence interval (CI) -5.5 to -0.4) (P=0.025) in comparison with that of the controls. The mean blood glucose declined by -0.21 mmol L(-1) (CI -0.33 to -0.09) in Group W1 and -0.13 mmol L(-1) (CI -0.25 to -0.01) in Group W2 compared to controls (P=0.03). Also the 2-h glucose concentration decreased in Groups W1 and W2 compared to controls. Systolic blood pressure, serum lipoproteins and insulin levels did not change in Study I or Study II. We conclude that our training program with the greatest exercise dose, exercise intensity 65% of VO2max and weekly expenditure of 1500 kcal had a minimal, positive effect on diastolic pressure and blood glucose, and the effect was similar in one or two daily exercise session groups. This exercise dose is probably close to the minimum to affect coronary risk factors in healthy postmenopausal women. To get a more pronounced and clinically relevant effect, a greater exercise dose is needed.     

Effect of oral contraceptives and hormone replacement therapy on bone mineral density in premenopausal and perimenopausal women: a systematic review

Seventy five articles on the effect of oral contraceptives and other hormone replacement on bone density in premenopausal and perimenopausal women were reviewed. The evidence was appraised using the Oxford Centre for Evidence-Based Medicine levels of evidence. There is good evidence for a positive effect of oral contraceptives on bone density in perimenopausal women, and fair evidence for a positive effect in "hypothalamic" oligo/amenorrhoeic premenopausal women. There is limited evidence for a positive effect in healthy and anorexic premenopausal women. In hypothalamic oligo/amenorrhoeic women, baseline bone density has been shown to be significantly lower than that in healthy controls, therefore the decision to treat is clinically more important. The ideal formulation(s) and duration of treatment remain to be determined by further longitudinal and prospective randomised controlled trials in larger subject populations.     

Effects of contract‐relax vs static stretching on stretch‐induced strength loss and length–tension relationship

The purpose of this study was to determine the acute effects of contract‐relax stretching (CRS) vs static stretching (SS) on strength loss and the length‐tension relationship. We hypothesized that there would be a greater muscle length‐specific effect of CRS vs SS. Isometric hamstring strength was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle P < 0.001; 11.7% at 90° P < 0.01; 5.6% at 70° nonsignificant (ns); 1.3% at 50° ns; ?3.7% at 30° ns. CRS: P < 0.001; stretching × angle P < 0.001; 17.7% at 90°, 13.4% at 70°, 11.4% at 50°, all P < 0.01, 4.3% at 30° ns]. The overall stretch‐induced strength loss was greater (P = 0.015) after CRS (11.7%) vs SS (3.7%). The muscle length effect on strength loss was not different between CRS and SS (stretching × angle × stretching technique P = 0.43). Contrary to the hypothesis, CRS did not result in a greater shift in the length–tension relationship, and in fact, resulted in greater overall strength loss compared with SS. These results support the use of SS for stretching the hamstrings.     

Effects of big‐five personality traits on the quality of relationship and satisfaction in Chinese coach–athlete dyads

The present study examined the influence of personality traits on the quality of the Chinese coach–athlete relationship and satisfaction through a dyadic research design. A total of 350 coach–athlete dyads completed a self‐report instrument that assessed personality traits, as well as perceptions of relationship quality and satisfaction with training. Results revealed that: (a) actor effects (i.e., actor's personality will predict his or her own perceptions of relationship quality) of personality traits, namely, conscientiousness, extroversion, and neuroticism, on both coaches' and athletes' perceptions of relationship quality and (b) partner effects (an actor's own personality will predict his or her partner's perceptions of relationship quality) of only athletes' personality, namely, conscientiousness, extroversion, and neuroticism, on their coaches' perceptions of relationship quality. The findings suggested that each relationship member's personality trait contributed independently to relationship quality, and both actor and partner effects of the relationship quality on satisfaction with training were found to be significant. In Chinese sports culture, there presents a unique dynamics of personality and relationship quality among coach–athlete dyad.     

Measurement of alveolar oxygen partial pressure in the rat lung using Carr‐Purcell‐Meiboom‐Gill spin–spin relaxation times of hyperpolarized 3He and 129Xe at 74 mT

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, ³He and ¹²⁹Xe, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin–spin relaxation rate (R₂) of ³He at low magnetic field strengths (<0.1 T) in vivo. R₂ measurements can be achieved efficiently using the Carr‐Purcell‐Meiboom‐Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr‐Purcell‐Meiboom‐Gill R₂ values of hyperpolarized ³He and ¹²⁹Xe in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin–spin relaxivity constants for ³He and ¹²⁹Xe were determined to be (5.2 ± 0.6) ×10^?6 Pa^?1 sec^?1 and (7.3 ± 0.4) ×10^?6 Pa^?1 s^?1 compared with spin‐lattice relaxivity constants of (4.0 ± 0.4) ×10^?6 Pa^?1 s^?1 and (4.3 ± 1.3) × 10^?6 Pa^?1 s^?1, respectively. In vivo experimental measurements of alveolar oxygen partial pressure using ³He in whole rat lung show good agreement (r² = 0.973) with predictions based on lung volumes and ventilation parameters. For ¹²⁹Xe, multicomponent relaxation was observed with one component exhibiting an increase in R₂ with decreasing alveolar oxygen partial pressure. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of music,video, and 360‐degree video on cycle ergometer exercise at the ventilatory threshold

Despite the seemingly ubiquitous presence of audiovisual stimuli in modern exercise facilities, there is a dearth of research examining the effects of audiovisual stimuli in combination during exercise. Accordingly, we examined the influence of a range of audiovisual stimuli on the improvement of affective, perceptual, and enjoyment responses to cycle ergometer exercise at the ventilatory threshold (VT), an intensity that is associated with the most affect‐related interindividual variability. A within‐subject design was employed, and participants (N = 18) completed a 25‐minute protocol that consisted of 2 minutes of seated rest, 5 minutes of warm‐up, 10 minutes of exercise at VT, 5 minutes of cooldown, and 3 minutes of seated rest. Participants exercised at VT under music, video, music‐video, 360‐degree video, 360‐degree video with music, and control conditions. The results revealed a condition × time interaction for perceived activation and a main effect of condition for state attention and perceived enjoyment. The 360‐degree video with music condition elicited the most positive affective valence, greatest perceived activation, most dissociative thoughts, and highest ratings of perceived enjoyment. The present findings indicate that audiovisual stimuli can influence affective, perceptual, and enjoyment responses to cycle ergometer exercise at the VT. Given the emerging support pertaining to a positive relationship between affective responses and exercise adherence, audiovisual stimuli, such as 360‐degree video with music, should be considered as a means by which to promote an enjoyable exercise experience.