Comprehensive cardiopulmonary profile of individuals with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) have low levels of cardiorespiratory fitness and previous studies have shown that these low levels of fitness have a physiological cause. During exercise, the cardiovascular, ventilatory and muscular systems are simultaneously active. While individual parameters of these systems have been investigated in DS before, the interaction between these parameters and systems have not been discussed in detail. Doing so may provide important insight regarding the aetiology of low cardiorespiratory fitness and which parameters of the cardiovascular, pulmonary and muscular systems are altered in individuals with DS compared with their peers without DS.

METHODS

Cardiopulmonary exercise tests were performed in healthy adults with and without DS. Parameters related to the cardiovascular, ventilatory and muscular systems were collected until VO_2peak . In total, 51 participants were included in analysis, of which 21 had DS.

RESULTS

Individuals with DS showed lower peak values for all collected outcomes (P ≤ 0.001) compared with those without DS, except for ventilatory threshold as a percentage of maximal oxygen uptake and V_E /VCO₂ slope, which were similar.

CONCLUSIONS

Our results show that individuals with DS present impairments across the cardiovascular, ventilatory and muscular aspects of the cardiopulmonary system.

Training responsiveness of cardiorespiratory fitness and arterial stiffness following moderate-intensity continuous training and high-intensity interval training in adults with intellectual and developmental disabilities

BACKGROUND

Cardiorespiratory fitness (CRF) prompts antiatherogenic adaptations in vascular function and structure. However, there is an extraordinary interindividual variability in response to a standard dose of exercise, wherein a substantial number of adults with intellectual and developmental disabilities (IDD) do not improve CRF. We (1) evaluated the effects of 12-month of moderate-intensity continuous training (MICT) on CRF and arterial stiffness and (2) tested whether an additional 3-month of high-intensity interval training (HIIT) would add to improvements in CRF responsiveness and arterial stiffness.

METHODS

Fifteen adults with mild-to-moderate IDD (male adults = 9, 30.1 ± 7.5 years old) met 3 days per week for 30 min MICT for 12 months, after which the incidence of CRF responsiveness was calculated (≥5.0% change in absolute peak VO₂ ). Thereafter, responders and non-responders started HIIT for 3 months with identical daily training load/frequency. Peak VO₂ , local and regional indices of arterial stiffness were assessed prior to and after each period.

RESULTS

Sixty per cent of the participants were non-responders following MICT, but the incidence dropped to 20% following HIIT (P = 0.03). Absolute peak VO₂ values reached significant difference from pre-intervention (+0.38 ± 0.08 L min^-1 , P = 0.001) only when HIIT was added. Lower limb pulse wave velocity (PWV) decreased following MICT (-0.8 ± 1.1 m s^-1 , P = 0.049), whereas central PWV only decreased following HIIT (-0.8 ± 0.9 m s^-1 , P = 0.013).

CONCLUSIONS

Cardiorespiratory fitness responsiveness and reductions in PWV to a 12-month MICT period in adults with IDD improved following a period of HIIT programme inducing higher metabolic stress.

Anthropometry does not fully explain low fitness among adults with Down syndrome

BACKGROUND

Cardiorespiratory fitness, expressed as peak oxygen uptake during exercise (VO₂ peak), is an important predictor of cardiovascular health and is related to anthropometry in the general population. Individuals with Down syndrome (DS) have reduced cardiorespiratory fitness and often exhibit different anthropometrics compared with the general population. Interestingly, the relation between anthropometry and cardiorespiratory fitness found in the general population is not apparent in individuals with DS. However, accurate measures with dual energy X-ray absorptiometry (DEXA) scan have not been used to investigate this relationship in this population. The purpose of this paper was to investigate the relationship between accurate measures of anthropometry and cardiorespiratory fitness in adults with DS compared with an age-matched and sex-matched control group.

METHODS

Anthropometrics (height, weight, waist and hip circumference, body composition via DEXA) and cardiorespiratory fitness (VO₂ peak, measured during a graded maximal exercise test) were assessed in adults with (n = 9; 25 ± 3 years; 6 male patients) and without DS (n = 10, 24 ± 4 years; 5 male patients).

RESULTS

Participants with DS were shorter (P < 0.01) than without DS and had a higher body mass index (P < 0.01), waist circumference (WC) (P = 0.026) and waist/height ratio (WHtR) (P < 0.01), but similar weight, body surface area (BSA), waist/hip ratio and body composition (P > 0.05). Participants with DS had significantly lower relative VO₂ peak and VO₂ peak corrected for total lean mass (TLM), but similar absolute VO₂ peak, compared with without DS. In participants with DS, only WC and WHtR were associated with VO₂ peak, whereas in participants without DS, height, weight, BSA, TLM, leg lean mass and body fat percentage were associated with VO₂ peak.

CONCLUSIONS

These results suggest that the relation between anthropometry and cardiorespiratory fitness found in the general population is not the same in adults with DS and that anthropometrics do not fully explain cardiorespiratory fitness in adults with DS. Further research into potential alternative explanations is required.

Single and combined effects of body composition phenotypes on carotid intima-media thickness

BACKGROUND

Central fatness might be a more sensitive predictor of atherosclerotic changes in children than are total body fat measures. However, it is unclear whether a total body fat measure coupled with an estimate of a more central pattern of fat accumulation predicts increased carotid intima-media-thickness (cIMT) better than either measure alone.

OBJECTIVE

The objective of the study is to identify the ability of a combination of simple anthropometric screening tools or a combination of objective measures of body composition to predict cIMT.

METHODS

cIMT was assessed on the common carotid artery in 349 children aged 11-12 years old (183 girls). Body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) were dichotomized according to established criteria and indices of total body (TBFI) and abdominal (ABFMI) fat were assessed by dual-energy X-ray absorptiometry and categorized (increased risk ≥85%). Single and combined associations among anthropometric and laboratorial measures with the risk of having increased cIMT (≥85%) and discriminatory performance were tested with logistic regression analysis and Receiver Operator Curve analysis.

RESULTS

Children with higher total fatness (BMI and TBFI) or higher central pattern of fat accumulation (WC, WHtR and BFMI) were in higher risk for increased cIMT [odds ratio (OR): 2.08-3.24). The risk for increased cIMT was not higher among children who coupled high total and high central fatness (OR: 2.27-3.10).

CONCLUSIONS

Combination of total and central measures of fat does not improve the prediction of increased cIMT in children. Simple surrogate measures of fatness can be used to predict increased cIMT urging special attention to those children who exhibit increased abdominal fat.

The role of fatness on physical fitness in adolescents with and without Down syndrome: The UP&DOWN study

BACKGROUND/OBJECTIVES

Adolescents with Down syndrome (DS) exhibit higher levels of fatness and low levels of physical fitness compared with those without DS. In adolescents without DS, fatness is tightly associated with physical fitness, but this association is unclear in adolescents with DS. The aim of this study was to examine the association between several markers of fatness and physical fitness in a relative large sample of adolescents with and without DS.

SUBJECTS/METHODS

A total of 111 adolescents with DS (41 females) aged 11-20 years participated in this cross-sectional study. We also included a sex-matched control group (ratio 1:2) of 222 adolescents without DS aged 12-18 years, participating in the UP&DOWN Study. The Assessing Level of Physical Activity (ALPHA) health-related fitness test battery for adolescents was used to assess fatness and physical fitness.

RESULTS

Our results show that fatness is not associated with low levels of physical fitness in adolescents with DS (that is, 3 of the 16 analyses identified differences in physical fitness variables by groups of fatness). In contrast, fatness, as expected, is associated with levels of physical fitness in adolescents without DS (that is, 13 of the 16 analyses identified differences in physical fitness variables by groups of fatness).

CONCLUSIONS

The present finding contributes to new knowledge by suggesting that the role of fatness on physical fitness is different in adolescents with and without DS, and consequently, the poor levels of physical fitness in adolescents with DS may be due to the syndrome rather than the high prevalence of obesity from this population.

Independent Association of Muscular Strength and Carotid Intima-Media Thickness in Children

The aim of this cross-sectional study was to examine the influence of muscular strength on carotid intima-media thickness (cIMT) in children, controlling for the effect of cardiorespiratory fitness (CRF) and central adiposity and to examine if differences among muscular strength tertiles translate to physiological differences. We assessed cIMT of the common carotid artery in 366 children between 11-12 years of age (191 girls). Measures included cIMT assessed with high-resolution ultrasonography, a maximal handgrip strength test, body fat mass and lean mass from DXA and CRF determined using a maximal cycle ergometer test. Association between muscular strength and cIMT adjusted for CRF and central adiposity, as measured by trunk fat, was tested with multiple linear regression analysis. Differences in risk factors among muscular strength groups were tested with ANOVA. The Muscular Strength Index (MSI) was inversely associated with cIMT independently of CRF and central adiposity (p<0.05). The low MSI group had the highest values of cIMT, waist circumference and systolic blood pressure and the lowest CRF (p<0.05). There was an inverse and independent association between muscular strength and cIMT. Low muscular strength was associated with higher levels of cardiovascular disease risk factors in children.

Effects of Walking with Blood Flow Restriction on Excess Post-exercise Oxygen Consumption

This study determined the influence of walking with blood flow restriction (BFR) on the excess post-exercise oxygen consumption (EPOC) of healthy young men. 17 healthy young men (22.1±2.9 years) performed graded treadmill exercise to assess VO_2peak. In a randomized fashion, each participant performed 5 sets of 3-min treadmill exercise at their optimal walking speed with 1-min interval either with or without BFR. Participants were then seated in a chair and remained there for 30 min of recovery. Expired gases were continuously monitored during exercise and recovery. BFR increased the O₂ cost of walking as well as its relative intensity and cumulative O₂ deficit (p<0.05). The EPOC magnitude after walking with BFR was greater than in the non-BFR condition (p<0.05). No differences between conditions were seen for the duration of EPOC. The EPOC magnitude was no longer different between conditions after controlling for the differences in relative intensity and in the cumulative O₂ deficit (p>0.05). These data indicate that walking with BFR increases the magnitude of EPOC. Moreover, they also demonstrate that such increment in EPOC is likely explained by the effects of BFR on walking relative intensity and cumulative O₂ deficit.

Blood pressure changes following aerobic exercise in Caucasian and Chinese descendants

Acute aerobic exercise produces post-exercise hypotension (PEH). Chinese populations have lower prevalence of cardiovascular disease compared to Caucasians. PEH may be associated cardiovascular disease through its influence on hypertension. The purpose of this study was to compare PEH between Caucasian and Chinese subjects following acute aerobic exercise. 62 (30 Caucasian and 32 Chinese, 50% male) subjects underwent measurement of peripheral and central hemodynamics as well as arterial and cardiac evaluations, 30 min and 60 min after 45 min of treadmill exercise. Caucasians exhibited significantly higher baseline BP than the Chinese. While the reduction in brachial artery systolic BP was greater in Caucasian than in the Chinese, there was no difference in changes in carotid systolic BP between the groups. The increase in cardiac output and heart rate was greater in the Chinese than Caucasians, but total peripheral resistance and leg pulse wave velocity decreased by a similar magnitude in the Chinese and Caucasian subjects. We conclude that acute aerobic exercise produces a greater magnitude of PEH in peripheral systolic BP in Caucasian compared to Chinese subjects. The different magnitude in PEH was caused by the greater increase in cardiac output mediated by heart rate, with no change in stroke volume. It is possible that initial BP differences between races influenced the findings.

Sex differences in ventricular-vascular coupling following endurance training

Introduction

Ventricular and vascular coupling is defined as the ratio of arterial elastance (Ea) to ventricular elastance (Elv) and describes the interaction between the heart and arterial system. There are sex differences in both arterial and ventricular function in response to both acute exercise and aerobic exercise training.

Purpose

To examine the effects of aerobic exercise training on elastances and the coupling ratio in young adult men and women. We hypothesized a reduction in the coupling ratio in both sexes due to a decrease in Ea that would be more pronounced in men and an increase in Elv that would be larger in women.

Methods

Fifty-three healthy, young adults completed the study. Central pulse wave velocity and heart volumes were measured before and after an 8-week aerobic training intervention. Elastances were calculated as Ea = end-systolic pressure/stroke volume and Elv = end-systolic pressure/end-systolic volume and indexed to body surface area.

Results

After the intervention, women augmented indexed and un-indexed Elv from 2.09 ± 0.61 to 2.52 ± 0.80 mmHg/ml, p < 0.05, and reduced the coupling ratio from 0.72 ± 18 to 0.62 ± 15, p < 0.05, while men maintained their pre-training ratio (from 0.66 ± 0.20 to 0.74 ± 0.21, p > 0.05). Women also reduced end-systolic pressure (from 91 ± 10 to 87 ± 10 mmHg), and both groups reduced central pulse wave velocity (from 6.0 ± 1.0 to 5.6 ± 0.6 m/s, p < 0.05).

Conclusion

We conclude that after 8 weeks of aerobic training, only women reduced their coupling ratio due to an increase in Elv. This suggests that aerobic exercise training elicits sex-dependent changes in the coupling ratio in young, healthy individuals.

Body composition and body fat distribution are related to cardiac autonomic control in non-alcoholic fatty liver disease patients

BACKGROUND/OBJECTIVES

Heart rate recovery (HRR), a cardiac autonomic control marker, was shown to be related to body composition (BC), yet this was not tested in non-alcoholic fatty liver disease (NAFLD) patients. The aim of this study was to determine if, and to what extent, markers of BC and body fat (BF) distribution are related to cardiac autonomic control in NAFLD patients.

SUBJECTS/METHODS

BC was assessed with dual-energy X-ray absorptiometry in 28 NAFLD patients (19 men, 51±13 years, and 9 women, 47±13 years). BF depots ratios were calculated to assess BF distribution. Subjects' HRR was recorded 1 (HRR1) and 2 min (HRR2) immediately after a maximum graded exercise test.

RESULTS

BC and BF distribution were related to HRR; particularly weight, trunk BF and trunk BF-to-appendicular BF ratio showed a negative relation with HRR1 (r=-0.613, r=-0.597 and r=-0.547, respectively, P<0.01) and HRR2 (r=-0.484, r=-0.446, P<0.05, and r=-0.590, P<0.01, respectively). Age seems to be related to both HRR1 and HRR2 except when controlled for BF distribution. The preferred model in multiple regression should include trunk BF-to-appendicular BF ratio and BF to predict HRR1 (r2=0.549; P<0.05), and trunk BF-to-appendicular BF ratio alone to predict HRR2 (r2=0.430; P<0.001).

CONCLUSIONS

BC and BF distribution were related to HRR in NAFLD patients. Trunk BF-to-appendicular BF ratio was the best independent predictor of HRR and therefore may be best related to cardiovascular increased risk, and possibly act as a mediator in age-related cardiac autonomic control variation.

Effect of sex on wasted left ventricular effort following maximal exercise

Wasted left ventricular effort (∆Ew) refers to work required of the left ventricle to eject blood that does not result in increased stroke volume and is related to left ventricular hypertrophy. Literature shows that men and women have differing ventricular and vascular responses to and following exercise. Our purpose was to determine how ∆Ew changes post-exercise in men and women and examine potential mechanisms. We hypothesized a reduction in ∆Ew that would be greater in men and that central pulse wave velocity and wave intensity (WIA) would be related to ∆Ew. Blood pressures, central pulse wave velocity (cPWV), and WIA were obtained at rest, 15 and 30 min after maximal exercise. Both sexes reduced ∆Ew post-maximal exercise (p>0.05 for interaction), but women had higher ∆Ew at each time point (p<0.05). The first peak of WIA increased 15 min post-exercise only in women (p<0.05). cPWV was attenuated (p<0.05) in women at 15 min and men at 30 min (p<0.05) post-exercise with a significant time by sex interaction (p<0.05). WIA (1st peak) was correlated (p<0.05) to ∆Ew in both sexes before and 15 min post-exercise, but cPWV was only associated with ∆Ew in men at 30 min post-exercise. We conclude that both sexes decrease ∆Ew after maximal exercise, but vascular and ventricular changes associated with the attenuation of ∆Ew are not uniform between sexes.

Symptomatic correlates of six-minute walk performance in persons with multiple sclerosis

BACKGROUND

The six-minute walk (6MW) test has been identified as a valid, reliable, and reproducible measure of endurance walking performance that differentiates persons with multiple sclerosis (MS) and controls and correlates with disability and walking impairment.

AIM

This study examined symptoms of fatigue, pain, and depression as correlates of 6MW performance and the possibility that such symptoms would account for the difference in 6MW distance between persons with MS and controls.

DESIGN

Observational.

SETTING

Research laboratory.

POPULATION

Sixty-six persons, 33 with MS and 33 controls matched on age, sex, height, and weight. METHODS. Participants completed the fatigue severity scale (FSS), short-form of the McGill pain questionnaire (SF-MPQ), and depression items of the hospital anxiety and depression scale (HADS-D) and then performed the six-minute walk (6MW) in a rectangular corridor.

RESULTS

There were statistically significant differences between groups in 6MW distance (p = 0.0001) and FSS (P=0.0001) and SF-MPQ (P=0.025), but not HADS-D (P>0.05), scores. 6MW distance was significantly correlated with FSS (P=-0.66), SF-MPQ (P=-0.38), and HADS-D (P=-0.33) scores in the overall sample, but 6MW distance was significantly correlated with only FSS scores in the separate samples of those with MS (P=-0.46) and controls (P=-0.46). Only group (β=0.32) and FSS scores (β=-0.53) explained variance in overall 6MW distance in a hierarchical, linear regression analysis.

CONCLUSION

This study provides new insight into the symptomatic correlates of 6MW performance and identifies fatigue as a possible target of interventions designed to improve walking endurance in MS.

CLINICAL REHABILITATION IMPACT

Clinicians and practitioners might consider targeting fatigue as a method of managing compromised endurance walking in persons with MS.

Comparison of the acute impact of maximal arm and leg aerobic exercise on arterial stiffness

Acute aerobic exercise decreases arterial stiffness based on the intensity of the exercise and the arterial segment studied. Arm exercise may differentially affect arterial stiffness compared to leg exercise but this has not been studied. We hypothesized that maximal aerobic exercise would reduce local peripheral pulse wave velocity i.e. femoral-dorsalis pedis (LPWV) following leg exercise and carotid-radial (APWV) following arm exercise without any crossover effect. The main purpose of the study is to compare the effects of maximal arm versus leg aerobic exercise on peripheral and central arterial stiffness. Fifteen healthy participants (9 males and 6 females, 25 ± 5 years) performed maximal arm-ergometer and leg-ergometer exercise in a randomized, crossover design. Peripheral and central pulse wave velocities (PWV) were obtained using applanation tonometry before and 10 min after each maximal exercise bout. 2 × 2 repeated measures analysis of variance was used to detect differences between conditions. There was a significant interaction in the APWV between the two exercise modes. However, there was no condition or interaction effect on LPWV following maximal arm versus leg exercise. There was no significant difference in central PWV between conditions or with time. There was no change in MAP (75 ± 6-77 ± 3) after maximal arm exercise as compared to the maximal leg exercise (73 ± 6-80 ± 2). Arm exercise produced a more generalized effect on arterial stiffness than leg exercise. The prescription of upper limb exercise may be considered for purposes of eliciting post-exercise systemic changes in arterial stiffness.

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes

Objective

To examine the responsiveness of cardiac autonomic function and baroreflex sensitivity (BRS) to exercise training in obese individuals without (OB) and with type 2 diabetes (ObT2D).

Design

Subjects were tested in the supine position and in response to a sympathetic challenge before and after a 16 week aerobic training program. All testing was conducted in the morning following a 12-hour fast.

Subjects

34 OB and 22 ObT2D men and women (40-60 yr)

Measurements

Heart rate variability (HRV) was measured at rest via continuous ECG (spectral analysis with the autoregressive approach) and in response to upright tilt. The dynamics of heart rate complexity were analyzed with sample entropy and Lempel-Ziv entropy, and BRS was determined via the sequence technique. Subjects were aerobically trained 4x/wk for 30-45 min for 16 wks.

Results

Resting HR decreased and total power (lnTP, msec²) of HRV increased in response to exercise training (P<0.05). High frequency power (lnHF) increased in OB subjects but not in OBT2D, and no changes occurred in ln low frequency/HF power with training. Upright tilt decreased lnTP and lnHF and increased LF/HF (P<0.01) but there were no group differences in the magnitude of these changes nor were they altered with training in either group. Tilt also decreased complexity (sample entropy and Lempel-Ziv; P<0.001), but there was no group or training effect on complexity. BRS decreased with upright tilt (P<0.01) but did not change with training. Compared to OB subjects the ObT2D had less tilt-induced changes in BRS.

Conclusion

Exercise training improved HRV and parasympathetic modulation (lnHF) in OB subjects but not in ObT2D, indicating plasticity in the autonomic nervous system in response to this weight-neutral exercise program only in the absence of diabetes. HR complexity and BRS were not altered by 16 wk of training in either OB or ObT2D individuals.

Cardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertension

AIM

Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP).

METHODS

Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained.

RESULTS

There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 +/- 3.0 pre- to 132 +/- 3.4 post-training vs. AE 142 +/- 4.0 pre- to 137 +/- 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 +/- 1.31 pre to 74 +/- 1.1 post vs. AE 80 +/- 1.7 pre to 77 +/- 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 +/- 67.28 to 161.26 +/- 61.49) and RE increasing this ratio (143.73 +/- 65.00 to 227.83 +/- 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 +/- 0.38 to 5.4 +/- 0.35 ms(2)) following AE and decreased (5.98 +/- 0.37 to 5.76 +/- 0.42 ms(2)) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 +/- 1.2 to 7.94 +/- 1.3 and 10.44 +/- 1.2 to 9.1 +/- 1.2 ms mmHg(-1) respectively, P = 0.021).

CONCLUSIONS

Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS.

Aerobic cost in elite female adolescent swimmers

Maximal performance in swimming depends on metabolic power and the economy of swimming. Thus, the energy cost of swimming (economy= VO(2)/V, C(s)) and maximal aerobic power (VO(2max)) in elite young female swimmers (n=10, age: 15.3+/-1.5 years) and their relationships to race times (50-1,000 m) and national ranking were examined. VO(2) increased exponentially with velocity (V), (VO(2)=5.95+(-10.58 V)+5.84 V(2)) to a maximal VO(2) of 2.71+/-0.50 L x min(-1) (46.7+/-8.2 mL x kg(-1) x min(-1)) at a free swimming velocity of 1.37+/-0.07 m x s(-1). C(s) was constant up to 1.2 m x s(-1) (21.5 mL x m(-1)), however was significantly higher at 1.36 m x s(-1) (27.3 mL x m(-1)). Peak [La] was 5.34+/-2.26 mM. C(s) expressed as a percentage of Cs at maximal swimming velocity was significantly correlated with race times and ranking across a number of distances. The data for these elite females demonstrate that the energy cost of swimming is a good predictor of performance across a range of distances. However, as swimming performance is determined by a combination of factors, these findings warrant further examination.

Effect of 4 weeks of aerobic or resistance exercise training on arterial stiffness, blood flow and blood pressure in pre- and stage-1 hypertensives

The benefits of aerobic exercise (AE) training on blood pressure (BP) and arterial stiffness are well established, but the effects of resistance training are less well delineated. The purpose of this study was to determine the impact of resistance vs aerobic training on haemodynamics and arterial stiffness. Thirty pre- or stage-1 essential hypertensives (20 men and 10 women), not on any medications, were recruited (age: 48.2 +/- 1.3 years) and randomly assigned to 4 weeks of either resistance (RE) or AE training. Before and after training, BP, arterial stiffness (pulse wave velocity (PWV)) and vasodilatory capacity (VC) were measured. Resting systolic BP (SBP) decreased following both training modes (SBP: RE, pre 136 +/- 2.9 vs. post 132 +/- 3.4; AE, pre 141 +/- 3.8 vs. post 136 +/- 3.4 mm Hg, P = 0.005; diastolic BP: RE, pre 78 +/- 1.3 vs post 74 +/- 1.6; AE, pre 80 +/- 1.6 vs. post 77 +/- 1.7 mm Hg, P = 0.001). Central PWV increased (P = 0.0001) following RE (11 +/- 0.9-12.7 +/- 0.9 ms(-1)) but decreased after AE (12.1 +/- 0.8-11.1 +/- 0.8 m s(-1). Peripheral PWV also increased (P = 0.013) following RE (RE, pre 11.5 +/- 0.8 vs. post 12.5 +/- 0.7 ms(-1)) and decreased after AE (AE, pre 12.6 +/- 0.8 vs post 11.6 +/- 0.7 m s(-1)). The VC area under the curve (VC(AUC)) increased more with RE than that with AE (RE, pre 76 +/- 8.0 vs. post 131.1 +/- 11.6; AE, pre 82.7 +/- 8.0 vs. post 110.1 +/- 11.6 ml per min per s per 100 ml, P = 0.001). Further, peak VC (VCpeak) increased more following resistance training compared to aerobic training (RE, pre 17 +/- 1.9 vs. post 25.8 +/- 2.1; AE, pre 19.2 +/- 8.4 vs post 22.9 +/- 8.4 ml per min per s per 100 ml, P = 0.005). Although both RE and AE training decreased BP, the change in pressure may be due to different mechanisms.

Acute resistance exercise reduces heart rate complexity and increases QTc interval

Acute resistance exercise (RE) has been shown to reduce cardiac vagal control. Whether this would in turn affect QTc interval (an index of ventricular depolarization/repolarization) or heart rate complexity is not known. Heart rate variability (HRV), heart rate complexity (SampEn), and QT interval (rate corrected using Bazett, Fridericia, Hodges, and Framingham) were measured before and 5 min after an acute RE bout in twelve healthy young men. Normalized high frequency power of HRV (an index of cardiac parasympathetic modulation; HF (nu)), and SampEn were reduced following RE (p < 0.05). Bazett corrected QTc interval increased following RE (p < 0.05). Change in HF (nu) from rest to recovery was correlated with both change in SampEn (r = 0.51, p < 0.05) and change in QTc interval for each method of correction (r = - 0.67 to - 0.70, p < 0.05). Acute RE reduced HF spectral power of HRV and this was related to both reduced heart rate complexity and increased QTc length. Thus, during recovery from acute RE, there is prolongation of depolarization and repolarization of the ventricles concomitant with reduced cardiac irregularity, and this may be related to a reduction in cardiac vagal control.

Cardiovascular Responses to Static Exercise: A Re-Appraisal

Traditional findings of circulatory responses to a bout of static exercise include an abrupt rise in systolic and diastolic blood pressure, small increases in cardiac output with no rise in stroke volume, and unaltered systemic vascular resistance. These characteristics are not, however, consistent with current concepts of circulatory adjustments to high intramuscular pressure and inability of the heart to generate increases in cardiac output by heart rate alone. When circulatory responses to static exercise are in considered on a per-beat basis, at times of circulatory flow, these conflicts are resolved, as systemic vascular resistance is observed to rise, and augmentation of cardiac output can be accounted for by improvements in myocardial contractility.

Gender differences in QTc interval in young, trained individuals with lower spinal cord injury

STUDY DESIGN

Cross-sectional comparison.

OBJECTIVE

To examine gender differences in rate-corrected QT interval (QTc), an index of ventricular depolarization/repolarization, in young, trained men and women with lower spinal cord injury (SCI) and able-bodied (AB) controls.

SETTING

University of Illinois at Urbana-Champaign, Exercise and Cardiovascular Research Lab, USA.

METHODS

Subjects consisted of 16 athletes with SCI (eight men and eight women) and 16 age-matched AB active controls (eight men and eight women). QT interval dynamics was derived from ECG recordings and rate corrected using the Bazett formula.

RESULTS

Men with SCI had QTc similar to that of AB men (369.3+/-7.5 versus 357.9+/-3.0 ms, P>0.05). Women with SCI had QTc similar to that of AB women (400.0+/-4.6 versus 385.2+/-6.5 ms, P>0.05). AB women had longer QTc interval than AB men, and SCI women had longer QTc than SCI men (P<0.05).

CONCLUSIONS

Gender differences in ventricular depolarization/repolarization are present in trained individuals with SCI. Thus, similar to their AB gender-matched peers, women with SCI have longer QTc intervals and may be at greater risk for the development of untoward cardiac arrhythmias than men with SCI.

Arterial stiffness and baroreflex sensitivity following bouts of aerobic and resistance exercise

We examined arterial stiffness, baroreflex sensitivity (BRS), and systolic arterial pressure (SAP) variability after an acute bout of aerobic exercise compared to resistance exercise. We hypothesized that arterial stiffness would be reduced after aerobic exercise, while it would be increased after resistance exercise, and these alterations would be associated with differential changes in BRS and SAP variability. Arterial stiffness, BRS, and SAP variability were assessed before and 20 min after a bout of aerobic exercise and resistance exercise in 13 male participants. Pulse wave velocity (PWV) was used to measure central (carotid-femoral) and peripheral (femoral-dorsalis pedis) arterial stiffness. BRS was derived via the sequence technique. Spectral decomposition of beat-to-beat SAP variability was used as an estimate of sympathetic vasomotor tone. A mode-by-time interaction (p < 0.001) was detected for central PWV, due to an increase in PWV (p < 0.05) following resistance exercise and a decrease in PWV following aerobic exercise (p < 0.05). A mode-by-time interaction was also detected for peripheral PWV (p < 0.05), due to a decrease in peripheral PWV following aerobic exercise (p < 0.05) with no change following resistance exercise. BRS was significantly lower following resistance compared with aerobic exercise (p < 0.004). SAP variability increased following resistance exercise (p < 0.05) but there was no interaction. In conclusion, aerobic exercise decreased both central and peripheral arterial stiffness, while resistance exercise significantly increased central arterial stiffness only. BRS was reduced after both bouts of exercise, but significantly greater reductions were seen following resistance exercise.

Evaluation of the Energy Cost of Playing a Dance Simulation Video Game in Overweight and Non-Overweight Children and Adolescents

The purpose of this study was to determine if there were any differences in the submaximal energy cost of movement between overweight (OW) and non-overweight (NO) children while playing a dance simulation video game, Dance Dance Revolution (DDR) and to determine if the cardiorespiratory measures obtained while playing the game met the American College of Sports Medicine (ACSM) recommendations for developing and maintaining cardiorespiratory fitness. Twenty-two children and adolescents (10 OW vs. 12 NO) participated in the study. Cardiorespiratory measurements were taken both during a maximal treadmill walking test and during a 12-minute Dance Dance Revolution protocol. The average absolute VO2 (OW: 917.1 +/- 257.1 vs. 590.6 +/- 147.9 mL . min (-1)) sustained over the DDR protocol was significantly higher in the OW group compared to the NO group. There was no significant difference in the average energy cost of movement when VO2 was normalized to fat-free mass (OW: 17.7 +/- 5.1 vs. NO: 17.3 +/- 3.9 mL . kgFFM (-1) . min (-1)). Both groups were above the minimal ACSM recommended heart rate intensity for developing and maintaining cardiorespiratory fitness when participating in the DDR protocol (OW: 64.83 % +/- 7.14 vs. NO: 64.51 % +/- 7.71), VO2 reserve, however, did not meet ACSM standards for developing and maintaining cardiorespiratory fitness.

Exercise is required for visceral fat loss in postmenopausal women with type 2 diabetes

This study examined the effects of aerobic exercise without weight loss, a hypocaloric high monounsaturated fat diet, and diet plus exercise (D+E) on total abdominal and visceral fat loss in obese postmenopausal women with type 2 diabetes. Thirty-three postmenopausal women (body mass index, 34.6 +/- 1.9 kg/m(2)) were assigned to one of three interventions: a hypocaloric high monounsaturated fat diet alone, exercise alone (EX), and D+E for 14 wk. Aerobic capacity, body composition, abdominal fat distribution (magnetic resonance imaging), glucose tolerance, and insulin sensitivity were measured pre- and postintervention. Body weight ( approximately 4.5 kg) and percent body fat ( approximately 5%) were decreased (P < 0.05) with the D and D+E intervention, whereas only percent body fat ( approximately 2.3%) decreased with EX. Total abdominal fat and sc adipose tissue (SAT) were reduced with the D and D+E interventions (P < 0.05), whereas visceral adipose tissue (VAT) decreased with the D+E and EX intervention, but not with the D intervention. EX resulted in a reduction in total abdominal fat, VAT, and SAT (P < 0.05) despite the lack of weight loss. The reductions in total abdominal fat and SAT explained 32.7% and 9.7%, respectively, of the variability in the changes in fasting glucose levels, whereas the reductions in VAT explained 15.9% of the changes in fasting insulin levels (P < 0.05). In conclusion, modest weight loss, through either D or D+E, resulted in similar improvements in total abdominal fat, SAT, and glycemic status in postmenopausal women with type 2 diabetes; however, the addition of exercise to diet is necessary for VAT loss. These data demonstrate the importance of exercise in the treatment of women with type 2 diabetes.

Physiological responses to weight-loss intervention in inactive obese African-American and Caucasian women

BACKGROUND

The physiological responses of inactive obese premenopausal African-American and Caucasian women to the identical exercise training and behavior modification program were compared.

METHODS

Inactive obese (96.1+/- 2.9 kg, BMI=34.8 +/- 0.7 kg/m2, % body fat=46.0 +/- 0.8; mean +/- SEM) premenopausal (36 +/- 2 yrs) African-American (n=10) and Caucasian (n=19) women were included. Resting metabolic rate (RMR), respiratory exchange ratio (RER), and maximal aerobic power (VO2max) were measured by indirect calorimetry, and body composition by plethysmography. Resting and maximal heart rates, blood glucose and lipids, and blood pressure were also measured. Treatment consisted of a 13-week diet and exercise behavior modification program. Group mean comparisons were made with a Student's "t"-test or an ANCOVA, which controlled for individual differences in body mass and lean body mass (LBM). Significance was set at p<0.05.

RESULTS

Initially, the groups were not significantly different in height, mass, BMI, age, % body fat, fat mass, LBM, girth measurements, RMR, RER, VO2max, blood pressure, or cholesterol profile. The number of weeks completed, number of exercise sessions completed, total minutes of exercise for the entire intervention, average minutes of daily exercise, and total estimated exercise energy expenditure were all similar between groups. Furthermore, both groups reported similar dietary compliance. Both groups reduced body mass, BMI, LBM, girth measurements, and increased VO2max (mlO2 x kg-1 x min-1) significantly and similarly.

CONCLUSIONS

African-American and Caucasian women respond the same physiologically to weight loss intervention. The higher prevalence in obesity for African-American women is not due to a different physiological response to diet and exercise.

Prediction of maximal heart rate in individuals with mental retardation

PURPOSE

It is well known that individuals with mental retardation (MR), especially those with Down syndrome (DS), have low maximal heart rates (MHR). We evaluated the ability to predict MHR in individuals with MR and DS in comparison with persons without MR.

METHODS

Subjects completed a maximal exercise test on the treadmill with metabolic and HR measurements. Stepwise multiple regression was used to develop prediction equations for subjects with MR (N = 276; 97 with DS) and without (N = 296) MR, ranging in age from 9-46 yr.

RESULTS

Subjects with MR exhibited significantly lower MHR (177 vs 185 beats.min(-1)) and VO2peak (33.8 vs 35.6 mL.kg-1.min(-1)). In subjects with MR, age was a poor predictor of MHR, Y = 189 - 0.59 (age) (R = 0.30, SEE = 13.8 beats.min-1; P < 0.01), but age was a better predictor for subjects without MR, Y = 205 - 0.64 (age) (R = 0.52, SEE = 9.9 beats.min(-1); P < 0.01). A large sample Z test indicated that these regression coefficients were significantly different (P < 0.01). However, adding DS to the regression improved the prediction for subjects with MR, Y = 210 - (0.56 age) - (15.5 DS) (R = 0.57; SEE = 11.8 beats.min(-1), P < 0.01).

CONCLUSION

MHR can be predicted with similar accuracy in subjects with and without MR, provided DS is accounted for in the equation for the subjects with MR.

Early-phase adaptations of traditional-speed vs. superslow resistance training on strength and aerobic capacity in sedentary individuals

We performed a randomized exercise training study to assess the effects of traditional Nautilus-style (TR) or superslow (SS) strength training on muscular strength, body composition, aerobic capacity, and cardiovascular endurance. Subjects were 14 healthy, sedentary women, 19-45 years of age (mean +/- SD age, 32.7 +/- 8.9 years), randomized to either the SS or TR training protocols and trained 3 times per week for 10 weeks. Measurements were taken both before and after training, which included a maximal incremental exercise test on a cycle ergometer, body composition, and 1 repetition maximum (1RM) tests on 8 Nautilus machines. Both groups increased their strength significantly on all 8 exercises, whereas the TR group increased significantly more than the SS group on bench press (34% vs. 11%), torso arm (anterior lateral pull-down) (27% vs. 12%), leg press (33% vs. 7%), leg extension (56% vs. 24%), and leg curl (40% vs. 15%). Thus, the TR group's improvement in total exercise weight lifted was significantly greater than that of the SS group after testing (39% vs. 15%). Exercise duration on the cycle ergometer and work rate significantly improved for both groups, but there was no group-by-training interaction. No significant differences were found for body composition or additional aerobic variables measured. Both strength training protocols produced a significant improvement in strength during a 10-week training period, but the TR protocol produced better gains in the absence of changes in percentage of body fat, body mass index, lean body mass, and body weight. In addition, strength training alone did not improve Vo2max, yet short-term endurance increased.

Evaluation of the BOD POD for estimating percentage body fat in a heterogeneous group of adult humans

The primary purpose of this investigation was to compare estimations of percentage body fat (%fat) using air displacement plethysmography (ADP) and hydrostatic weighing (HW) in a heterogeneous (age and %fat) sample of the population. Of secondary importance was to determine whether there were differences between the two methods among lean (n = 32), average (n = 34) and overweight (n = 29) subsets of this sample. A total of 95 adults (men 27, women 68) ranging in age from 18-52 years volunteered for this study. Test-retest reliability for %fat ADP (n = 16) was 0.99 with a technical error of 0.75%fat and a coefficient of variation of 3.4%fat. Mean body density using ADP [1.048 (SD 0.016) g.ml-1] was not significantly different when compared to HW [1.049 (SD 0.017) g.ml-1], which corresponded to a non-significant difference in %fat [22.5 (SD 7.3)% ADP compared to 22.0 (SD 7.6)% HW]. Regression analysis provided the equation: %fat HW = 0.9121%fat ADP + 1.5123; r = 0.88, SEE = 3.6, which did not differ significantly from the line of identity. Data for the subsets revealed a significant overestimation of %fat ADP [16.4 (SD 4.8)%] compared to HW [14.1 (SD 3.2)%] (P = 0.001) for lean individuals while no difference was found in the average [21.9 (SD 4.4)%fat ADP compared to 22.0 (SD 3.4)%fat HW] or overweight [29.9 (SD 5.5)%fat ADP compared to 30.8 (SD 4.1)%fat HW] subsets. Measuring %fat by ADP is a highly reliable method and valid when compared to HW for a heterogeneous sample of adults. The ADP method requires little expertise to operate, is quick to perform, and may be more accommodating for certain individuals compared to HW. However, in this study ADP was less valid for lean individuals. Further investigation is warranted to determine the bias of this method for subsets of the population which may be outside the average range of %fat (men 15.4%-22.0%, women 18.4%-28.5%).

Effects of aerobic exercise on low back pain patients in treatment

BACKGROUND CONTEXT

Aerobic exercise (AE) has been prescribed to improve fitness and well-being in apparently healthy individuals and cardiac, orthopedic, and other patient populations. AE has not previously been studied as a sole treatment for low back pain patients (LBPP).

PURPOSE

This study evaluated the effects of low to moderate aerobic exercise as an adjunct treatment for LBPP, 30 to 60 years of age, in a neurosurgical practice during a 2.5-year follow-up to an initial 10-week exercise program. The purpose of this study was to determine the effects of short- and long-term AE on LBPP. The initial 10-week phase compared AE and nonexercising controls on mood states and pain/symptoms.

STUDY DESIGN/SETTING

A matched stratified design was used to input LBPP with similar previous clinical treatments as well as age and sex into AE or control groups.

PATIENT SAMPLE

After screening 68 LBPP from a New England private neurosurgical practice, 40 patients met qualification criteria, and 35 volunteered for this AE research study. The LBPP in this study were 30 to 60 years old and had the following medical diagnoses: herniated nucleus pulposus at one or more lumbar levels, degenerative discopathy, lumbosacral strain, and spinal canal and/or foraminal stenosis.

OUTCOME MEASURES

The measure of mood states was the Profile of Mood States, and the measure of pain was the Brief Pain Inventory. The 2.5-year follow-up phase compared AE and nonexercise patients on the following treatment variables: medical office visits for pain/symptoms, physical therapy referrals, epidural steroid injections for pain/symptoms, prescription of pain medications, and work status.

METHODS

Thirty-five LBPP were matched stratified into an AE or nonexercise control group for a 10-week exercise program. After the 10-week exercise program, all subjects were given the opportunity to cross over to the opposite group. Those patients choosing to exercise were advised to follow a low to moderate aerobic exercise prescription (walking or cycling, 60% age-predicted maximal heart rate, 4 days per week for 45 minutes per day). None of the original AE group crossed over to the nonexercise group because of symptoms relating to their previous exercise participation. All participants were contacted at 6-month intervals, and the number of medical office visits for pain/symptoms, physical therapy referrals, number of epidural steroid injections, and number of prescriptions for pain was charted for 2.5 years. Work status was evaluated by comparing the change in number of patients not working, working part time, working full time, or number changing from full time to part time or not working from randomization to the end of follow-up. Patients following the exercise prescription at least 50% of the time were compared with those exercising less than 50% of the time during the 2.5-year follow-up. Significance was determined at the.05 level using Fisher's exact test or the Kruskal-Wallis test.

RESULTS

The initial 10-week AE phase of the study indicated that low to moderate AE significantly improved mood profile (AE X=-9.58; control X=19.11; p<.01) but did not alter pain levels. AE patients in the 2.5-year follow-up phase received significantly fewer pain medication prescriptions (AE X=2.76; control X=13.35; p<.02) and were given fewer physical therapy referrals (AE X=0.17; control X=1.64; p<.002). There was no significant difference in the number of medical office visits for pain or epidural blocks administered to either group. Work status was improved only in exercising patients (AE X=+0.24; control X=-0.35; p<.04).

CONCLUSIONS

Low to moderate aerobic exercise appears to improve mood states and work status and reduce the need for physical therapy referrals and pain medication prescriptions for LBPP in the care of a neurosurgeon.

Both atenolol and propranolol blunt the fibrinolytic response to exercise but not resting fibrinolytic potential

This randomized, double-blind trial found that tissue plasminogen activator activity increased and plasminogen activator inhibitor-1 activity decreased significantly more with exercise during placebo treatment than during treatment with beta blockade. These results suggest that beta blockade blunts the fibrinolytic response to maximal exercise.

Physical activity and high density lipoprotein cholesterol levels: what is the relationship?

High density lipoprotein cholesterol (HDL-C) levels are strongly, inversely and independently associated with coronary heart disease (CHD). Increased physical activity is associated with reduced CHD mortality. This protection against CHD may partially be explained by the increase in HDL-C levels observed following aerobic exercise training. Many also agree that an exercise threshold needs to be met before such favourable changes in HDL-C metabolism can occur. Most likely, the exercise-induced changes in HDL-C are the result of the interaction amongst exercise intensity, frequency, duration of each exercise session and length of the exercise training period. Although a relative contribution of each exercise component (intensity, duration and frequency) is also likely, it has not been established. There is also substantial support for a dose-response relationship. Favourable changes in HDL-C appear to occur incrementally and reach statistical significance at approximately 7-10 miles per week or 1200 to 1600kcal. Exercise-induced changes in HDL-C may also be gender dependent. The volume of exercise required to increase HDL-C levels appears to be substantially more for women than men. This perhaps is due to higher HDL-C levels in women at baseline compared with men. However, the many other health benefits derived from increased physical activity should encourage women to participate in regular exercise regardless of the exercise effects on HDL-C levels. A practical approach in prescribing exercise for patients is to use moderate intensity exercises (70 to 80% of predicted maximal heart rate), 3 to 5 times per week, for a total of 7 to 14 miles per week. This is equivalent to approximately 1200 to 1600kcal per week. Moderate to low intensity exercise should be preferred because such exercise carries a lower risk for cardiac complications. In addition, patients are more likely to participate and sustain a lower than higher intensity exercise programme. It is also important to recognise that other modes of physical activity can also be encouraged for patients. Such activities should be associated with similar increases in HDL-C levels as long as they meet or exceed the caloric expenditure of 1200 to 1600kcal (7 to 14 miles per week of jogging).

Hemostatic responses to maximal exercise in oral contraceptive users

OBJECTIVE

This study examined the effect of exercise on markers of fibrinolysis and coagulation in users and nonusers of oral contraceptives.

STUDY DESIGN

Fourteen oral contraceptive users and 14 nonusers performed a maximal exercise test on a cycle ergometer. Blood samples were collected before and immediately after the completion of the test. A repeated-measures analysis of variance was used for statistical analysis with values considered significant at P =.05.

RESULTS

Acute maximal exercise resulted in significant increases in tissue plasminogen activator activity in both groups. There was a trend toward a smaller increase in tissue plasminogen activator activity in oral contraceptive users, but the difference between groups was not statistically significant. Plasminogen activator inhibitor 1 activity was reduced with exercise in both groups but with a significantly greater decrease observed in the nonusers (P <.0001). Prothrombin fragment 1+2 was significantly higher (P <.0001) in the oral contraceptive group but did not change with exercise. Epinephrine levels before and after exercise were similar between the 2 groups, but postexercise norepinephrine concentrations were significantly lower (P =.026) in the oral contraceptive users.

CONCLUSION

These data suggest that oral contraceptive use blunts the fibrinolytic response to exercise. This, together with increased coagulation activation in oral contraceptive users, may alter the hemostatic balance during exercise.

Substrate utilization during submaximal exercise in obese and normal-weight women

In this study we compared substrate use at submaximal intensities of a maximal graded exercise test (GXT) with that derived from equivalent intensities during continuous submaximal steady-state exercise in obese and normal-weight women. Sedentary obese (n = 20, body fat > 30%) and normal-weight (n = 15, body fat < or =30%) women performed three treadmill tests with concurrent metabolic measurements. Maximal oxygen consumption (VO2max) was determined using the Bruce protocol, followed by two, randomly assigned, continuous 15-min, steady-state exercise bouts, on different days; one bout at 50% and one bout at 75% VO2max. Analysis of variance revealed no significant differences between groups for blood lactate or respiratory exchange ratio (R) values at any point during exercise. Therefore, obese and normal-weight group data were combined for subsequent analyses. The R at 50% VO2max from the GXT [0.83 (0.01)] was significantly (P < 0.05) lower than at 8 min [0.90 (0.01)] and 15 min [0.89 (0.01)] of steady-state exercise, whereas at 75% VO2max, the GXT R [0.96 (0.01)] was similar to that seen at 8 min [0.96 (0.01)] and at 15 min of steady-state exercise [0.93 (0.01)]. Blood lactate values at 50% VO2max were similar between the GXT [1.66 (0.10) mM] and steady-state exercise [1.65 (0.09) mM], but at 75% VO2max the GXT blood lactate values [2.58 (0.21) mM] were lower than after 15 min of steady-state exercise [4.65 (0.46) mM]. Total exercise fat oxidation was greater at 50% compared to 75% VO2max. There was no difference in substrate use between sedentary obese and normal-weight women either at rest or during steady-state exercise at the same relative intensity. Total fat oxidation was greater during low- (50% VO2max) compared to high-intensity (75% VO2max) exercise. Data from a GXT cannot be used to predict R or substrate utilization values for the purpose of exercise prescription.