Low Aerobic Fitness Research Articles

Physical activity for paediatric rheumatic diseases: standing up against old paradigms.

Over the past 50 years it has become clear that physical inactivity is associated with chronic disease risk. For several rheumatic diseases, bed rest was traditionally advocated as the best treatment, but several levels of evidence support the imminent paradigm shift from the prescription of bed rest to physical activity in individuals with paediatric rheumatic diseases, in particular juvenile systemic lupus erythematosus, juvenile idiopathic arthritis, juvenile fibromyalgia, and juvenile dermatomyositis. Increasing levels of physical activity can alleviate several symptoms experienced by patients with paediatric rheumatic diseases, such as low aerobic fitness, pain, fatigue, muscle weakness and poor health-related quality of life. Moreover, the propensity of patients with paediatric rheumatic diseases to be hypoactive - often due to social self-isolation, overprotection, and fear and/or ignorance on the part of parents, teachers and health practitioners - can be detrimental to general disease symptoms and function. In support of this rationale, a growing number of studies have demonstrated that the systemic benefits of exercise training clearly outweigh the risks in these diseases. In this sense, health professionals are advised to assess, track and fight against physical inactivity and sedentary behaviour on a routine basis, as they are invaluable health risk parameters in rheumatology.

Aerobic fitness, muscular strength and obesity in relation to risk of heart failure

ObjectiveLow physical fitness and obesity have been associated with higher risk of developing heart failure (HF), but their interactive effects are unknown. Elucidation of interactions among these common modifiable factors...

Aerobic fitness influences rest and heart rate recovery on young men regardless of body mass index

Obesity and aerobic fitness influence resting (HRrest) and heart rate recovery (HRR), and the evaluation of these parameters show a relevant clinical application. This study aimed to evaluate the influence of body mass index (BMI) and aerobic fitness on HRR after maximal exercise in healthy young men. Twenty nine untrained men (21.37 ± 2.11 years) were divided according to BMI (normal weight ≤24.9, overweight ≥25 and obese ≥30 kg m−2) and subsequently divided into higher aerobic fitness (125.00 ± 21.71 W) and lower aerobic fitness (72.69 ± 24.38 W), based on the median (105 W) aerobic fitness assessed through the workload at the heart rate variability threshold (HRVT). There were no differences (p > 0.05) for HRrest, aerobic fitness or HRR between the three BMI groups. Blood glucose and lipid profile were similar among groups, regardless of BMI and aerobic fitness. However, the young men with higher aerobic fitness showed lower HRrest (70.48 ± 6.54 vs 81.54 ± 6.46 bpm), HRR1 (163.1 ± 9.2 vs 170.1 ± 7.6 bpm), HRR2 (147.2 ± 7.4 vs 154.6 ± 8.1 bpm) and HRR3 (139.2 ± 6.9 vs 145.8 ± 8.0 bpm), compared to their pairs with lower aerobic fitness. Additionally, HRrest and the HRVT workload were significantly (p < 0.05) associated with HRR2 (r 0.49 and −0.49), HRR3 (r 0.60 and −0.53), HRR4 (r 0.53 and −0.47) and HRR5 (r 0.48 and −0.47). Aerobic fitness influenced HRrest and HRR in untrained young men, regardless of BMI.

Aerobic fitness is associated with low cardiovascular disease risk: the impact of lifestyle on early risk factors for atherosclerosis in young healthy Swedish individuals - the Lifestyle, Biomarker, and Atherosclerosis study.

BackgroundThe progression of cardiovascular disease (CVD) and atherosclerosis is slow and develops over decades. In the cross-sectional Swedish Lifestyle, Biomarker, and Atherosclerosis study, 834 young, self-reported healthy adults aged 18.0–25.9 years have been studied to identify early risk factors for atherosclerosis.PurposeThe aims of this study were to 1) assess selected cardiometabolic biomarkers, carotid intima–media thickness (cIMT) as a marker of subclinical atherosclerosis, and lifestyle-related indicators (food habits, handgrip strength, and oxygen uptake, VO2 max); 2) analyze the associations between cIMT and lifestyle factors; and 3) identify subjects at risk of CVD using a risk score and to compare the characteristics of subjects with and without risk of CVD.MethodBlood samples were taken in a fasting state, and food habits were reported through a questionnaire. cIMT was measured by ultrasound, and VO2 max was measured by ergometer bike test. The risk score was calculated according to Wildman.ResultcIMT (mean ± standard deviation) was 0.50±0.06 mm, and VO2 max values were 37.8±8.5 and 42.9±9.9 mL/kg/min, in women and men, respectively. No correlation was found between aerobic fitness expressed as VO2 max (mL/kg/min) and cIMT. Using Wildman’s definition, 12% of the subjects were classified as being at risk of CVD, and 15% had homeostasis model assessment of insulin resistance. A total of 35% of women and 25% of men had lower high-density lipoprotein cholesterol than recommended. Food habits did not differ between those at risk and those not at risk. However, aerobic fitness measured as VO2 max (mL/kg/min) differed; 47% of the subjects at risk had low aerobic fitness compared to 23% of the nonrisk subjects (P<0.001).ConclusionHigh aerobic fitness is associated with low CVD risk in Swedish young adults. The high prevalence of young adults observed with unfavorable levels of high-density lipoprotein cholesterol and homeostasis model assessment of insulin resistance raises concerns about future CVD risk.

Voluntary Running Attenuates Metabolic Dysfunction in Ovariectomized Low-Fit Rats.

Ovariectomy and high-fat diet (HFD) worsen obesity and metabolic dysfunction associated with low aerobic fitness. Exercise training mitigates metabolic abnormalities induced by low aerobic fitness, but whether the protective effect is maintained after ovariectomy and HFD is unknown. This study determined whether, after ovariectomy and HFD, exercise training improves metabolic function in rats bred for low intrinsic aerobic capacity. Female rats selectively bred for low (LCR) and high (HCR) intrinsic aerobic capacity (n = 30) were ovariectomized, fed HFD, and randomized to either a sedentary (SED) or voluntary wheel running (EX) group. Resting energy expenditure, glucose tolerance, and spontaneous physical activity were determined midway through the experiment, whereas body weight, wheel running volume, and food intake were assessed throughout the study. Body composition, circulating metabolic markers, and skeletal muscle gene and protein expression were measured at sacrifice. EX reduced body weight and adiposity in LCR rats (-10% and -50%, respectively; P < 0.05) and, unexpectedly, increased these variables in HCR rats (+7% and +37%, respectively; P < 0.05) compared with their respective SED controls, likely because of dietary overcompensation. Wheel running volume was approximately fivefold greater in HCR than LCR rats, yet EX enhanced insulin sensitivity equally in LCR and HCR rats (P < 0.05). This EX-mediated improvement in metabolic function was associated with thee gene upregulation of skeletal muscle interleukin-6 and interleukin-10. EX also increased resting energy expenditure, skeletal muscle mitochondrial content (oxidative phosphorylation complexes and citrate synthase activity), and adenosine monophosphate-activated protein kinase activation similarly in both lines (all P <0.05). Despite a fivefold difference in running volume between rat lines, EX similarly improved systemic insulin sensitivity, resting energy expenditure, and skeletal muscle mitochondrial content and adenosine monophosphate-activated protein kinase activation in ovariectomized LCR and HCR rats fed HFD compared with their respective SED controls.

Combined Iron Deficiency and Low Aerobic Fitness Doubly Burden Academic Performance among Women Attending University

Academic success is a key determinant of future prospects for students. Cognitive functioning has been related to nutritional and physical factors. Here, we focus on iron status and aerobic fitness in young-adult female students given the high rate of iron deficiency and declines in fitness reported in this population. We sought to explore the combined effects of iron status and fitness on academic success and to determine whether these associations are mediated by cognitive performance. Women (n = 105) aged 18-35 y were recruited for this cross-sectional study. Data were obtained for iron biomarkers, peak oxygen uptake (VO2peak), grade point average (GPA), performance on computerized attention and memory tasks, and motivation and parental occupation. We compared the GPA of groups 1) with low compared with normal iron status, 2) among different fitness levels, and 3) by using a combined iron status and fitness designation. Mediation analysis was applied to determine whether iron status and VO2peak influence GPA through attentional and mnemonic function. After controlling for age, parental occupation, and motivation, GPA was higher in women with normal compared with low ferritin (3.66 ± 0.06 compared with 3.39 ± 0.06; P = 0.01). In analyses of combined effects of iron status and fitness, GPA was higher in women with normal ferritin and higher fitness (3.70 ± 0.08) than in those with 1) low ferritin and lower fitness (3.36 ± 0.08; P = 0.02) and 2) low ferritin and higher fitness (3.44 ± 0.09; P = 0.04). Path analysis revealed that working memory mediated the association between VO2peak and GPA. Low iron stores and low aerobic fitness may prevent female college students from achieving their full academic potential. Investigators should explore whether integrated lifestyle interventions targeting nutritional status and fitness can benefit cognitive function, academic success, and postgraduate prospects.

The relationship between low aerobic fitness and injury in the military

The relationship between low aerobic fitness and injury in the military

Physiological Effort in Submaximal Fitness Tests Predicts Weight Loss in Overweight and Obese Men with Prostate Cancer in a Weight Loss Trial.

BackgroundObesity and weight gain after the diagnosis of prostate cancer are associated with an increased risk of prostate cancer recurrence and mortality; individualized plans to help prostate cancer survivors maintain or lose weight may be beneficial for recurrence risk reduction. Herein, we explore whether gains in cardiovascular fitness predict successful weight loss in men participating in a weight loss trial (NCT01886677).MethodsForty men were randomized to receive twice-weekly in-person and telephone-based guidance on calorie-restricted diets and aerobic exercise to promote ~0.91 kg/week weight loss, or wait-list control. Thirty-two men completed submaximal VO2 Treadmill Tests (TT), anthropometric measures and two 24-hour dietary recalls at baseline and follow-up. For this secondary analysis, study arms were combined and associations between baseline and longitudinal changes in physiological effort (PE, measured by heart rate during TT), predicted VO2max, caloric intake and weight loss were analyzed.ResultsMen lost 3.4 kg in 50 ± 23 days on the study. Multivariate linear regression indicated weight change was associated with change in PE at stage 2TT (Partial R = 0.635, p < 0.001), days on study (Partial R = −0.589, p = 0.002) and change in caloric intake (Partial R = 0.457, p = 0.019).ConclusionsUntrained men experiencing elevated heart rates during stage 2TT at baseline were able to achieve greater weight loss over the study period; this association was strengthened by a decrease in PE at the same level from baseline to follow-up concomitant with reduced caloric intake. Therefore, for these middle-aged and older men with lower aerobic fitness, exercise appears to be a key factor in achieving higher degrees of weight loss.

Stress Fractures: Etiology, Epidemiology, Diagnosis, Treatment, and Prevention.

Stress fractures are part of a continuum of changes in healthy bones in response to repeated mechanical deformation from physical activity. If the activity produces excessive repetitive stress, osteoclastic processes in the bone may proceed at a faster pace than osteoblastic processes, thus weakening the bone and augmenting susceptibility to stress fractures. Overall stress fracture incidence is about three cases per 1,000 in active duty Servicemembers, but it is much higher among Army basic trainees: 19 per 1,000 for men and 80 per 1,000 for women. Well-documented risk factors include female sex, white ethnicity, older age, taller stature, lower aerobic fitness, prior physical inactivity, greater amounts of current physical training, thinner bones, cigarette smoking, and inadequate intake of vitamin D and/or calcium. Individuals with stress fractures present with focal tenderness and local pain that is aggravated by physical activity and reduced by rest. A sudden increase in the volume of physical activity along with other risk factors is often reported. Simple clinical tests can assist in diagnosis, but more definitive imaging tests will eventually need to be conducted if a stress fracture is suspected. Plain radiographs are recommended as the initial imaging test, but magnetic resonance imaging has higher sensitivity and is more likely to detect the injury sooner. Treatment involves first determining if the stress fracture is of higher or lower risk; these are distinguished by anatomical location and whether the bone is loaded in tension (high risk) or compression (lower risk). Lowerrisk stress fractures can be initially treated by reducing loading on the injured bone through a reduction in activity or by substituting other activities. Higher-risk stress fractures should be referred to an orthopedist. Investigated prevention strategies include modifications to physical training programs, use of shock absorbing insoles, vitamin D and calcium supplementation, modifications of military equipment, and leadership education with injury surveillance.

Diurnal Patterns of Physical Activity in Relation to Activity Induced Energy Expenditure in 52 to 83 Years-Old Adults.

BackgroundAgeing is associated with a declining physical activity level (PAL) and changes in the diurnal activity pattern. Changes in the activity pattern might help explaining the age-associated reduction of physical activity.ObjectiveThe aims were to investigate diurnal activity patterns within groups of older adults classified by PAL, to investigate diurnal activity patterns within age-groups and to investigate the association between the drop in activity and aerobic fitness.MethodsThirty-one healthy subjects aged between 52 and 83y were recruited for the study. Subjects were divided in sedentary (PAL<1.75), moderately active (1.75<PAL<1.90), and active (1.90<PAL) older adults with energy expenditure measurements obtained with the doubly labelled water technique. Diurnal activity patterns were based on activity counts from an accelerometer during wake time and then divided in four quarters of equal time length. Additionally, aerobic fitness was measured as maximal oxygen uptake.ResultsSubjects had a PAL between 1.43 and 2.34 and an aerobic fitness between 18 and 49 ml/kg/min. Overall, activity patterns showed a peak in the first quarter of wake time (around 10AM) followed by a gradual decline of, on average, 5% per hour. Active subjects reached their peak in the first quarter and remained active until after the third quarter (11% drop each quarter on average). Moderately active and sedentary subjects reached their peak during the second quarter with a decrease during the third quarter (respectively 29% and 17% drop each quarter on average). The drop in physical activity between the first and the second half of the wake time was negatively associated with aerobic fitness (r = -0.39, p<0.05).ConclusionActive older adults maintained a larger amount of body movement for longer during their wake time. Diurnal physical activity declined more in adults ≥66 years old with lower aerobic fitness.

Health associations with meeting new 24-hour movement guidelines for Canadian children and youth

The study objective was to examine whether meeting the new Canadian 24-hour movement guidelines was associated with health indicators in a representative sample of Canadian children and youth. Cross-sectional findings are based on 4157 (1239 fasting subsample) children and youth aged 6–17years from cycles 1–3 of the Canadian Health Measures Survey (CHMS). Sleep and screen time were subjectively measured while moderate- to vigorous-intensity physical activity (MVPA) was accelerometer-determined. Health indicators in the full sample (body mass index (BMI) z-scores, waist circumference, blood pressure, behavioral strengths and difficulties score (lower=better), and aerobic fitness) and fasting subsample (triglycerides, high-density lipoprotein (HDL)-cholesterol, C-reactive protein, and insulin) were measured. Meeting the overall guidelines was defined as: 9–11 hour/night (5–13years) or 8–10 hour/day (14–17years) of sleep, ≤2 hour/day of screen time, and ≥60 minute/day of MVPA. Compared to meeting all three recommendations, meeting none, one, and two recommendations were associated with a higher BMI z-score, waist circumference, and behavioral strengths and difficulties score and lower aerobic fitness in a gradient pattern (Ptrend<0.05). Additionally, compared to meeting all three recommendations, meeting none and one recommendation were associated with higher systolic blood pressure and insulin (Ptrend<0.05). Finally, compared to meeting all three recommendations, meeting no recommendations was associated with higher triglycerides and lower HDL-cholesterol (Ptrend<0.05). Collectively, meeting more recommendations within the 24-hour movement guidelines was associated with better overall health. Since a small proportion (17%) of this representative sample was meeting the overall guidelines, efforts to promote adoption are needed.

Interactive effects of obesity and physical fitness on risk of ischemic heart disease.

Background/ObjectivesObesity and low physical fitness are known risk factors for ischemic heart disease (IHD), but their interactive effects are unclear. Elucidation of interactions between these common, modifiable risk factors may help inform more effective preventive strategies. We examined interactive effects of obesity, aerobic fitness, and muscular strength in late adolescence on risk of IHD in adulthood in a large national cohort.Subjects/MethodsWe conducted a national cohort study of all 1,547,407 military conscripts in Sweden during 1969–1997 (97–98% of all 18-year-old males each year). Aerobic fitness, muscular strength, and body mass index (BMI) measurements were examined in relation to IHD identified from outpatient and inpatient diagnoses through 2012 (maximum age 62 years).ResultsThere were 38,142 men diagnosed with IHD in 39.7 million person-years of follow-up. High BMI or low aerobic fitness (but not muscular strength) was associated with higher risk of IHD, adjusting for family history and socioeconomic factors. The combination of high BMI (overweight/obese vs. normal) and low aerobic fitness (lowest vs. highest tertile) was associated with highest IHD risk (incidence rate ratio, 3.11; 95% CI, 2.91–3.31; P<0.001). These exposures had no additive and a negative multiplicative interaction (i.e., their combined effect was less than the product of their separate effects). Low aerobic fitness was a strong risk factor even among those with normal BMI.ConclusionsIn this large cohort study, low aerobic fitness or high BMI at age 18 was associated with higher risk of IHD in adulthood, with a negative multiplicative interaction. Low aerobic fitness appeared to account for a similar number of IHD cases among those with normal vs. high BMI (i.e., no additive interaction). These findings suggest that interventions to prevent IHD should begin early in life and include not only weight control but aerobic fitness, even among persons of normal weight.

Interactive Effects of Aerobic Fitness, Strength, and Obesity on Mortality in Men.

Low aerobic fitness, low muscular strength, and obesity have been associated with premature mortality, but their interactive effects are unknown. This study examined interactions among these common, modifiable factors, to help inform more-effective preventive interventions. This national cohort study included all 1,547,478 military conscripts in Sweden during 1969-1997 (97%-98% of all men aged 18 years each year). Aerobic fitness, muscular strength, and BMI measurements were examined in relation to all-cause and cardiovascular mortality through 2012 (maximum age, 62 years). Data were collected/analyzed in 2015-2016. Low aerobic fitness, low muscular strength, and obesity at age 18 years were independently associated with higher all-cause and cardiovascular mortality in adulthood. The combination of low aerobic fitness and muscular strength (lowest versus highest tertiles) was associated with twofold all-cause mortality (adjusted hazard ratio=2.01; 95% CI=1.93, 2.08; p<0.001; mortality rates per 100,000 person years, 247.2 vs 73.8), and 2.6-fold cardiovascular mortality (2.63; 95% CI=2.38, 2.91; p<0.001; 43.9 vs 8.3). These factors also had positive additive and multiplicative interactions in relation to all-cause mortality (their combined effect exceeded the sum or product of their separate effects; p<0.001), and were associated with higher mortality even among men with normal BMI. Low aerobic fitness, low muscular strength, and obesity at age 18 years were associated with increased mortality in adulthood, with interactive effects between aerobic fitness and muscular strength. Preventive interventions should begin early in life and include both aerobic fitness and muscular strength, even among those with normal BMI.

Interactive effects of physical fitness and body mass index on risk of stroke: A national cohort study.

High body mass index (BMI) and low physical fitness are risk factors for stroke, but their interactive effects are unknown. Elucidation of interactions between these modifiable risk factors can help inform preventive interventions in susceptible subgroups. National cohort study of all 1,547,294 military conscripts in Sweden during 1969-1997 (97-98% of all 18-year-old males). Standardized aerobic capacity, muscular strength, and body mass index measurements were examined in relation to stroke identified from inpatient and outpatient diagnoses through 2012 (maximum age 62 years). Sixteen thousand nine hundred seventy-nine men were diagnosed with stroke in 39.7 million person-years of follow-up. High body mass index, low aerobic fitness, and (less strongly) low muscular fitness were associated with higher risk of any stroke, ischemic stroke, and intracerebral hemorrhage, independently of family history and sociodemographic factors. High body mass index (overweight/obese vs. normal) and low aerobic capacity (lowest vs. highest tertile) had similar effect magnitudes, and their combination was associated with highest stroke risk (incidence rate ratio, 2.36; 95% CI, 2.14-2.60; P < 0.001). Aerobic capacity and muscular strength had a positive additive and multiplicative interaction (P < 0.001), indicating that low aerobic capacity accounted for more strokes among men with low compared with high muscular strength. High body mass index and low aerobic capacity in late adolescence are associated with increased risk of stroke in adulthood. Low aerobic capacity and low muscular strength also have a synergistic effect on stroke risk. These findings suggest that preventive interventions should include weight control and aerobic fitness early in life, and muscular fitness especially among those with low aerobic capacity.

Relationship Between Aerobic Fitness, the Serum IGF-1 Profiles of Healthy Young Adult African American Males, and Growth of Prostate Cancer Cells.

The growth of prostate tumors is mediated by the bioavailability of androgens and insulin-like growth factors. This study tested the hypothesis that healthy young adult African American men exhibiting low aerobic capacity (fitness) have serum insulin-like growth Factor-1 (IGF-1) and testosterone levels that promote growth of prostate cancer cells. A cross-sectional data research design was used to study groups of 18- to 26-year-old healthy men exhibiting low and moderate aerobic fitness, based on their peak oxygen consumption (VO2peak). The individual serum levels of IGF-1, IGF-1 binding protein-3 (IGFBP-3), and testosterone were measured. In vitro growth of androgen-dependent LNCaP prostate tumor cells was measured after incubation in culture medium fortified with each subject's serum. Aerobic capacity was significantly greater in the moderate-fitness group than in the low-fitness group without an intergroup difference in body mass index. The serum IGF-1 concentration was significantly higher in the low-fitness group in the absence of an intergroup difference in serum testosterone. The serum IGFBP-3 concentration was significantly lower in the low-fitness group. Prostate tumor cell growth was significantly greater in the cultures incubated in media containing the sera of the low-fitness group than in the sera of the moderate-fitness group. These findings suggest that moderate aerobic fitness in young adults may decrease the circulating levels of free IGF-1 and lower the potential to support growth of prostate cancer cells.

Lower aerobic fitness levels among adolescents of a city in southern Brazil

Study design: Cross sectional study. Objective: To analyze the association between lower levels of aerobic fitness and sociodemographic factors, lifestyle and excess body fatness in students. Methods: Study with 84 adolescents aged 14 to 19 years from southern Santa Catarina. Aerobic fitness was assessed by the modified Canadian Aerobic Fitness test-mCAFT. Sociodemographic variables, sexual maturation and lifestyle were assessed self-administered questionnaire. Excess body fatness assessed the sum of skin folds triceps and subscapular. Results: The prevalence of lower level of aerobic fitness was 83.3%. The female gender (OR: 5,99; IC95%: 1,40-25,52) and adolescents little physically active (OR: 5,62; IC95%: 1,21-26,38) had low levels aerobic fitness. Conclusion: The factors had associated with low levels of aerobic fitness were females and physical inactivity

Factors Influencing Running-Related Musculoskeletal Injury Risk Among U.S. Military Recruits.

Running-related musculoskeletal injuries among U.S. military recruits negatively impact military readiness. Low aerobic fitness, prior injury, and weekly running distance are known risk factors. Physical fitness screening and remedial physical training (or discharging the most poorly fit recruits) before entry-level military training have tended to reduce injury rates while decreasing attrition, training, and medical costs. Incorporating anaerobic running sessions into training programs can offset decreased weekly running distance and decrease injury risk. Varying lower extremity loading patterns, stride length or cadence manipulation, and hip stability/strengthening programming may further decrease injury risk. No footstrike pattern is ideal for all runners; transitioning to forefoot striking may reduce risk for hip, knee, or tibial injuries, but increase risk for calf, Achilles, foot or ankle injuries. Minimal evidence associates running surfaces with injury risk. Footwear interventions should focus on proper fit and comfort; the evidence does not support running shoe prescription per foot type to reduce injury risk among recruits. Primary injury mitigation efforts should focus on physical fitness screening, remedial physical training (or discharge for unfit recruits), and continued inclusion of anaerobic running sessions to offset decreased weekly running distance.

Walking Economy is Impaired in Older Men and Women with Type 2 Diabetes.

We compared the walking economy in older participants with and without type 2 diabetes. Walking economy was determined in 115 older participants with type 2 diabetes and 130 older control participants without diabetes by continuously measuring oxygen uptake during a treadmill test in which the work rate was at a constant speed of 2 mph and a grade of 0% for a duration of 10 minutes. Participants also completed a Balke treadmill protocol for the determination of peak oxygen uptake, defined as the highest oxygen uptake value attained during the final work stage attained. Fractional utilization was then calculated as the walking economy oxygen uptake divided by peak oxygen uptake, expressed as a percentage. Compared to those without diabetes, participants with type 2 diabetes were older (p=0.042), had higher prevalence of men (p=0.034), obesity (p=0.010), chronic kidney disease (p=0.020), peripheral artery disease (p=0.024), and had a higher body mass index (p=0.025), and waist/hip ratio (p=0.006). After adjusting for these variables, the participants with diabetes had higher walking economy (p<0.001), fractional utilization (p<0.001), and lower peak oxygen uptake (p<0.001) than those without diabetes (p<0.001). Older men and women with type 2 diabetes are less economical when they ambulate at a given speed than compared to control participants without diabetes, independent of their greater co-morbid burden. The impaired walking economy in the diabetic participants is further magnified by their lower aerobic fitness, thereby leading to a higher fractional utilization of oxygen consumed during a given walking task.

Arterial Stiffness in Physically Active Children with Congenital Heart Disease and Low Aerobic Fitness

Arterial Stiffness in Physically Active Children with Congenital Heart Disease and Low Aerobic Fitness

Influence Of Aerobic Fitness On The Thermophysiological Responses In Compensable And Uncompensable Heat Stress

PURPOSE: To examine the influence of aerobic fitness in groups matched for anthropometric characteristics on the thermal and thermoeffector responses in compensable (CO) and uncompensable (UN) heat stress, during exercise at matched relative and absolute work rates. Previous work has been confounded by differences in body characteristics and the selection of external work rate. METHODS: Eight high (HI) (mean [SD] V˙O2max = 58.73[6.28] mL.kg-1.min-1) and eight low aerobic fitness (LO) (46.53[6.73] mL.kg-1.min-1) males, matched for body mass, surface area and % body fat volunteered. LO cycled at 60 W (ABS) in 34 °C, 20 % rh. HI completed the same condition, plus an additional test to match the relative intensity of the LO at ABS as a % of V˙O2max (REL). There were two phases in each trial: 1) Compensable phase - 60 minutes at the specified external work rate, CO was confirmed by a plateau in rectal temperature (Tre). 2) Uncompensable phase – immediately following the compensable phase, ambient temperature (Tdb) was increased by 1 °C every 5 minutes, UN was confirmed by an inflection in Tre (Treinfl). Tdb, Tre, change in Tre from rest (ΔTre), metabolic heat production (M) back sweat rate (SRBack) and laser Doppler forearm skin blood flow (SkBF) were measured at end of the compensable phase and Treinfl identified. Data were analysed by independent t-tests. RESULTS: 1) Compensable phase - there were no differences in Tdb, Tre, ΔTre or SkBF between fitness groups in ABS or REL (all p=>0.05) or M in ABS (p=0.633). HI had higher SRBack in both ABS (p=0.002) and REL (p<0.001) and M in REL (p=0.011). 2) Uncompensable phase – there were no differences in Tdb, Tre, ΔTre or SkBF between fitness groups in ABS or REL (all p=>0.05) or M in ABS (p=0.361) at Treinfl. HI had higher SRBack in both ABS (p=0.005) and REL (p<0.001) and M in REL (p=0.012) at Treinfl. CONCLUSION: When anthropometric characteristics are controlled between HI and LO, HI have greater SR than LO regardless of M. This greater SR is likely due to an earlier onset and greater sensitivity of sweating as an adaptation from aerobic training. This improved thermoregulatory function appears to allow the HI to offset the greater M at the matched REL and thermoregulate and transition into UN at a similar Tdb with a similar Tre, if the greater SR is able to evaporate freely into the environment.