Sclerostin and bone turnover markers response to cycling and running at the same moderate-to-vigorous exercise intensity in healthy men

BACKGROUND

Recreational cycling is a popular activity which stimulates and improves cardiovascular fitness. The corresponding benefits for bone are unclear.

PURPOSE

This study examined the effect of running (high-impact) vs. cycling (low-impact), at the same moderate-to-vigorous exercise intensity, on markers of bone formation (N-terminal propeptide of type I collagen, PINP) and bone resorption (C-telopeptide of type I collagen, CTX-1), a non-collagenous bone remodeling marker (osteocalcin), as well as bone-modulating factors, including parathyroid hormone (PTH), irisin (myokine) and sclerostin (osteokine).

METHODS

Thirteen healthy men (23.7 ± 1.0 y) performed two progressive exercise tests to exhaustion (peak VO₂) on a cycle ergometer (CE) and on a treadmill (TM). On subsequent separate days, in randomized order, participants performed 30-min continuous running or cycling at 70% heart rate reserve (HRR). Blood was drawn before, immediately post- and 1 h into recovery.

RESULTS

PTH transiently increased (CE, 51.7%; TM, 50.6%) immediately after exercise in both exercise modes. Sclerostin levels increased following running only (27.7%). Irisin increased following both running and cycling. In both exercise modes, CTX-1 decreased immediately after exercise, with no significant change in PINP and osteocalcin.

CONCLUSION

At the same moderate-to-vigorous exercise intensity, running appears to result in a greater transient sclerostin response compared with cycling, while the responses of bone markers, PTH and irisin are similar. The longer-term implications of this differential bone response need to be further examined.

Effects of High-Intensity Interval Running Versus Cycling on Sclerostin, and Markers of Bone Turnover and Oxidative Stress in Young Men

This study compared sclerostin's response to impact versus no-impact high-intensity interval exercise in young men and examined the association between exercise-induced changes in sclerostin and markers of bone turnover and oxidative stress. Twenty healthy men (22.3 ± 2.3 years) performed two high-intensity interval exercise trials (crossover design); running on treadmill and cycling on cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥ 90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise), and 5 min, 1 h, 24 h, and 48 h following each trial. Serum levels of sclerostin, cross-linked telopeptide of type I collagen (CTXI), procollagen type I amino-terminal propeptide (PINP), thiobarbituric acid reactive substances (TBARS), and protein carbonyls (PC) were measured. There was no significant time or exercise mode effect for PINP and PC. A significant time effect was found for sclerostin, CTXI, and TBARS with no significant exercise mode effect and no significant time-by-mode interaction. Sclerostin increased from pre- to 5 min post-exercise (47%, p < 0.05) and returned to baseline within 1 h following the exercise. CTXI increased from pre- to 5 min post-exercise (28%, p < 0.05), then gradually returned to baseline by 48 h. TBARS did not increase significantly from pre- to 5 min post-exercise but significantly decreased from 5 min to 48 h post-exercise. There were no significant correlations between exercise-induced changes in sclerostin and any other marker. In young men, sclerostin's response to high-intensity interval exercise is independent of impact and is not related to changes in bone turnover and oxidative stress markers.

Targeting inflammation to influence cognitive function following spinal cord injury: a randomized clinical trial

STUDY DESIGN

This study was a randomized, parallel-group, controlled clinical trial.

OBJECTIVES

The purpose of this study was to examine the efficacy of targeting inflammation as a means of improving cognitive function in individuals with spinal cord injury.

SETTING

Participants were recruited from the Niagara region of Ontario Canada and all testing occurred on-site at Brock University.

METHODS

Indices of memory and verbal learning were assessed by means of the California Verbal Learning Test (CVLT). Inflammation and concentrations of neuroactive compounds related to the kynurenine pathway were assessed via a number of pro- and anti-inflammatory cytokines, as well as tryptophan, kynurenine and several large neutral amino acids. All assessments were performed at baseline as well as at 1 month and 3 months during a 3-month intervention by means of an anti-inflammatory diet.

RESULTS

Despite a reduction in inflammation, all measures of the CVLT, including list A, trial 1 (P=0.48), learning slope (P=0.46), long delay free recall (P=0.83), intrusions (P=0.61) and repetitions (P=0.07), showed no significant group × time interaction.

CONCLUSION

It may be possible that the reduction in inflammation achieved in the current study was insufficient to induce substantial changes in indices of verbal learning and memory. Alternatively, as these participants likely underwent years of previous chronic inflammation, the underlying hippocampal damage may have negated potential improvements induced by acute reductions in inflammation.

Differential sclerostin and parathyroid hormone response to exercise in boys and men

SUMMARY

Physical exercise benefits bone structure and mineralization, especially in children. Immediately following high-impact exercise, PTH increased and returned to resting values within 24 h in both groups, while sclerostin increased in men but not in boys. The underlying mechanisms and implication of this age-related differential response are unclear.

INTRODUCTION

Circulating sclerostin, a negative regulator of bone, decreases during puberty and increases in adulthood. Parathyroid hormone (PTH) is inversely related to sclerostin. In mice, sclerostin decreases following 24 h of mechanical stimulation. Its response to exercise in humans and, especially in children, in whom high-impact physical exercise benefits bone structure and mineralization is unclear. The aim of this study was to investigate the acute response of sclerostin to a single exercise session of high mechanical loading and the corresponding changes in PTH in boys and men.

METHODS

Twelve boys (10.2 ± 0.4 years old) and 17 young men (22.7 ± 0.8 years old) underwent a protocol of plyometric exercises (total 144 jumps). Blood samples were collected pre-, 5 min, 1 h, and 24 h post-exercise.

RESULTS

Boys had significantly higher resting values of sclerostin compared with men (150 ± 37 vs. 111 ± 34 pg/ml, respectively, p = 0.006). Following exercise, sclerostin markedly increased in men but this response was attenuated in boys (at 5 min: 51 ± 38 vs. 14 ± 21%, respectively, p = 0.005). PTH levels were similar in boys and men at rest and throughout the 24-h study period, increasing significantly (p < 0.001) 5 min after exercise, decreasing after 60 min post-exercise and returning to resting values within 24 h.

CONCLUSION

Although the PTH response was similar in boys and men, the sclerostin response was greater in men. The combined increases in PTH and sclerostin immediately post-exercise appear contrary to the accepted osteogenic effect of exercise. The underlying mechanisms and full implication of the differential response between children and adults need to be further examined.

Maturity status in male child and adolescent athletes

AIM

Early-maturing individuals may be at an advantage in some sports. The purpose of this study was to compare maturity status between competitive male child (10-12 years old) and adolescent (14-16 years old) athletes and minimally-active, age-matched controls.

METHODS

In total, 224 males were included in the study. Children (n=115) included minimally-active boys (n=34), soccer players (n=26), gymnasts (n=25) and hockey players (n=30). Adolescents (n=109) included minimally-active adolescents (n=31), soccer players (n=30), gymnasts (n=17) and hockey players (n=31). Sexual maturity was assessed using secondary sex characteristics and salivary testosterone concentration (sT). Skeletal age was also assessed, using quantitative ultrasound (Sunlight BonAgeTM).

RESULTS

Within each age group, no differences were observed between sport groups in chronological age, sT or pubertal age. In children, hockey players were more skeletally mature (12.43±1.36 years) than all other groups (11.0±1.0; 11.6±1.4 and 11.7±1.4 years for soccer, gymnasts and controls, respectively). In adolescents, hockey players and gymnasts had higher skeletal maturity (16.8±1.5 and 16.9±1.6 years, respectively; P<0.05) than controls (15.99±1.13 years).

CONCLUSION

While sexual and hormonal maturity does not appear to differ between similar-aged athletes of different sports, the results suggest greater skeletal maturity in hockey players, even before puberty.

Relative importance of body composition, osteoporosis-related behaviors, and parental income on bone speed of sound in adolescent females

INTRODUCTION

Adolescence provides a unique opportunity to employ strategies aimed at optimizing peak bone mass yet there are limited studies on the relationship between specific social constructs, osteoporosis-related behaviors, and bone health status in adolescent females. The purpose of this study was to examine associations between bone speed of sound (SOS) and body composition, osteoporosis-related health behaviors, and parental income in adolescent females.

METHODS

Four hundred forty-two female students in grades 9-12 from schools in Southern Ontario, Canada were measured for height, body mass, and percent body fat and completed a battery of instruments to assess osteoporosis-related health behaviors. Bone SOS was measured by transaxial quantitative ultrasound at the distal radius and midtibia.

RESULTS

Percent body fat was a negative correlate of tibial SOS. No significant correlation was found between physical activity and bone SOS yet physical activity was negatively related to adiposity. Hierarchical regression showed that age and percent body fat were the most important predictors of the variance in tibial SOS scores, with calcium intake having a weaker, yet significant, relationship. Age was the only statistically significant predictor of radial SOS. Users of oral contraceptives had higher radial SOS when controlling for age. Higher parental income was not associated with bone SOS but positive associations between parental income, daily calcium intake, and weekly physical activity were noted.

CONCLUSIONS

Bone SOS is reduced in adolescent females with increased adiposity, whereas it is positively influenced by oral contraceptives and daily calcium intake.

The need for energy equilibrium

Human bioenergetics has been extensively assessed by means of field proxies (ie, cardiorespiratory fitness field tests) during the last two decades. A systematic review of the germane literature, however, suggests considerable controversy as to whether the present tests lead to valid measurements of energy expenditure/utilisation. The present paper suggests that current modalities of field testing being used as predictive models for bioenergetics may suffer from methodological limitations, stemming primarily from inappropriate design. A major weakness in the theoretical basis of proxies is that, although based on field measurements, it seeks to predict laboratory bioenergetics which, in turn, are used to provide information on field performance. Hence, it seems reasonable that the number of transformations increases the potential for error and may have significant impact on the prediction of bioenergetics. Recent studies asserted the importance of achieving 'energy equilibrium' between the reference standard and each proxy. The suggested approach involves designing proxies that closely simulate each laboratory protocol used as reference standard. The theoretical bases of previous and contemporary approaches are discussed in an attempt to increase the validity of current proxy assessments.

Onset of puberty, menstrual frequency, and body fat in elite rhythmic gymnasts compared with normal controls

OBJECTIVES

To assess the prevalence of delayed menarche and abnormal menstrual patterns, as well as the association of menstrual status with physical training in elite rhythmic gymnasts from Greece and Canada.

METHODS

Fifteen Greek (mean (SEM) age 14.5 (0.2) years) and 30 Canadian (mean (SEM) age 14.7 (0.4) years) rhythmic gymnasts were surveyed for age at menarche, menstrual frequency, and training profile, and measured for height, weight, and percentage body fat (%BF). Seventy eight healthy adolescents served as country specific non-active controls: 38 Greek non-athletes (mean (SEM) age 14.5 (0.1) years) and 40 Canadian non-athletes (mean (SEM) 14.2 (0.1) years).

RESULTS

Of the Greek gymnasts, 79% had not yet menstruated compared with 34% of the Canadian gymnasts. Menarche was significantly (p<0.01) delayed in the rhythmic gymnasts (composite mean 13.8 (0.3) years, n = 45) compared with the controls (composite mean 12.5 (0.1) years, n = 78). There was no significant difference between Greek and Canadian gymnasts for the age at menarche (14.2 (0.3) v 13.6 (1.2) years respectively). Menstrual irregularities were reported in 78% (61% oligomenorrhoeic and 17% amenorrhoeic) of the menarcheal athletes. Menarcheal gymnasts were found to be significantly (p<0.05) taller and heavier, with a higher %BF and a lower training frequency and training duration (p<0.05) than the premenarcheal gymnasts. Overall, the mean %BF of the gymnasts was significantly lower (p<0.05) than that of the control subjects. The Canadian controls exhibited a significantly (p<0.05) greater %BF than the Greek controls of the same age.

CONCLUSION

Delayed menarche, menstrual irregularities, and low body fat are common in elite rhythmic gymnasts. Premenarcheal gymnasts train more often and for longer, and have a lower body mass index and less body fat, than menarcheal gymnasts. Prospective studies are needed to explore further these and other factors associated with delayed menarche and menstrual irregularities in female athletes.

Continuous versus intermittent exercise effects on urinary excretion of albumin and total protein

Several studies have reported post-exercise increases of urinary concentrations of plasma proteins. However, under normal conditions, through mechanisms of size and electrical charge selection, the kidney restricts the clearance of molecules as large as albumin. Post-exercise increases in albuminuria occur following the physiological stress of intense exercise, most likely as a result of the exercise induced blood acidity changes which lead to a change in the arrangement of the albumin molecule, and subsequently the filtration characteristics of the glomerular capillary wall. The purpose of the present study was therefore to determine the extent to which different types of exercise could induce a transient condition of post-exercise increases in the urinary output of total protein and albumin. All 14 males, who agreed to participate in the study, performed a continuous and an intermittent cycling protocol on a stationary bicycle ergometer. The results showed that: a) intermittent exercise had a greater influence than continuous exercise on the total output of urine albumin, and of urine total protein; b) concentrations of blood pH and blood lactate, were associated with changes in the clearance of urine albumin and urine total protein. Post-exercise proteinuria response seems to be transient and therefore renal trauma is not suspected at the early stages of observation. Furthermore, these results indicate that the kidney undergoes distinct physiological adjustments during exercise, and that these adjustments are relative to the intensity of the exercise stress.

Longitudinal evaluation of supervised versus unsupervised exercise programs for the treatment of osteoporosis

The efficacy of an exercise program was investigated in a study of 89 post-menopausal women with osteoporosis over a 5-year follow-up period. The study attempted to examine and compare potential differences in bone mineral density (BMD), incidence of fracture, and loss of height, between a group of patients (n = 42) who attended the supervised exercise program in the hospital, and a group (n = 47) who exercised at home. Habitual physical activity, as estimated using the Harvard Alumni Questionnaire, and a Physical Activity Index were combined to obtain an estimate of overall weekly caloric expenditure over the 5-year period. The exercise program involved weight-bearing aerobic activities of moderate intensity, and muscle strengthening exercise using free weights. The mean percentage change for the lumbar BMD was + 4.4% in the hospital group and +3.4% in the home group while for the femoral neck BMD was + 1.1% in the hospital group and -0.9% in the home group. There was a significant reduction in the number of fractures and no significant loss of height over the 5-year follow-up period for both groups. As the correlation between BMD and weekly caloric expenditure of the subjects was not significant, no conclusion can be drawn as to the minimum level of caloric expenditure necessary in order to retard bone loss. It was concluded that for the post-menopausal women with osteoporosis who participated in the program it was possible to stabilize their height and the BMD of the lumbar site, and to reduce fractures over the 5-year study period regardless if they exercised in a supervised or in an unsupervised setting.

The effect of lower body positive pressure on the cardiovascular response to exercise in sedentary and endurance-trained persons with paraplegia

Exercise intolerance in persons with paraplegia (PARAS) is thought to be secondary to insufficient venous return and a subnormal cardiac output at a given oxygen uptake. However, these issues have not been resolved fully. This study utilized lower-body positive pressure (LBPP) as an intervention during arm crank exercise in PARAS in order to examine this issue. Endurance-trained (TP, n = 7) and untrained PARAS (UP, n = 10) with complete lesions between T6 and T12, and a control group consisting of sedentary able-bodied subjects (SAB, n = 10) were tested. UP and TP subjects demonstrated a diminished cardiac output (via CO2 rebreathing) during exercise compared to SAB subjects. Peak oxygen uptake (O2peak) remained unchanged for all groups following LBPP. LBPP resulted in a significant decrease in heart rate (HR) in UP and TP (P < 0.05), but not SAB subjects. LBPP produced an insignificant increase in cardiac output (Q) and stroke volume (SV). The significant decrease in HR in both PARA groups may indicate a modest hemodynamic benefit of LBPP at higher work rates where circulatory sufficiency may be most compromised. We conclude that PARAS possess a diminished cardiac output during exercise compared to the able-bodied, and LBPP fails to ameliorate significantly their exercise response irrespective of the conditioning level. These results support previous observations of a lower cardiac output during exercise in PARAS, but indicate that lower-limb blood pooling may not be a primary limitation to arm exercise in paraplegia.