Chantal Vella

Oxygen cost of ventilation during incremental exercise to VO2 max

Objective:  Evidence of significant oxygen requirements for ventilation during exercise (exercise hyperpnoea) prompted the investigation into whether the oxygen cost of ventilation affects the presence of a whole‐body VO2 plateau at maximal exercise. The purposes of this study were to: (i) use isocapnic hyperpnoea trials to determine the oxygen cost of ventilation (VO2VENT) across a range of ventilation (VE); (ii) determine the mean VO2VENT at maximal exercise expressed as a percentage of whole‐body VO2 max; and (iii) determine if a plateau in VO2 is more evident when the VO2VENT is subtracted from whole‐body VO2 at maximal exercise.

Muscle Activation Patterns and Patellofemoral Pain in Cyclists

INTRODUCTION Patellofemoral pain syndrome (PFPS) is pervasive and debilitating in the sport of cycling. Currently, little is known about the underlying mechanism causing patellofemoral pain in cyclists. PURPOSE The purpose of this study was to determine whether temporal differences in the muscle activity of the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF) were correlated to patellofemoral pain in cycling. METHODS Ten healthy cyclists (six women and four men, height = 1.74 ± 0.10 cm, weight = 71.9 ± 16.5 kg, cycling experience = 199.5 ± 82 miles · wk(-1)) and seven cyclists with PFPS (one woman and six men, height = 1.84 ± 0.08 cm, weight = 89.8 ± 9.4 kg, cycling experience = 228 ± 51 miles · wk(-1)) volunteered to participate in this study. Each participant completed a 10-min cycling trial during which surface EMG was recorded for the VM, VL, ST, and BF muscles. Sagittal plane knee kinematic data were recorded using an electrogoniometer. RESULTS An ANOVA revealed no significant difference between groups for the differences in onset times of the VM and VL (P = 0.805). There were significant differences between groups for the differences in offset time of the VM and VL (P = 0.032), the differences in onset time of BF and ST (P < 0.001), and the differences in offset time of the ST and BF (P = 0.024). Root mean square values for BF activity were significantly higher in the PFPS group compared with the control (CTL) group (P < 0.01), and ST values were significantly lower in the PFPS group compared with the CTL group (P < 0.01). Root mean square values for BF were significantly greater than ST activity in the PFPS group (P < 0.01) but not in the CTL group (P > 0.05). CONCLUSION The results of this study indicate that trained cyclists with PFPS exhibit altered temporal characteristics in muscle activation patterns compared with trained cyclists without PFPS.

Associations of Insulin Resistance With Cardiovascular Risk Factors and Inflammatory Cytokines in Normal-Weight Hispanic Women

OBJECTIVE To investigate the associations of markers of insulin resistance with cardiovascular disease risk factors and inflammation in young, normal-weight, Hispanic women. RESEARCH DESIGN AND METHODS Seventy-one normal-weight (BMI <25 kg/m2) Hispanic women (age, 20–39 years) participated in a fasting blood draw for glucose, insulin, lipids, and inflammatory markers; a glucose tolerance test; anthropometric and blood pressure measurements; body composition by dual-energy x-ray absorptiometry; and measurements of cardiorespiratory fitness via Vo2max and daily physical activity by accelerometer. RESULTS Six percent of participants had impaired fasting glucose, 14% had impaired glucose tolerance, and 48% had at least one cardiovascular disease risk factor. Homeostasis model assessment of insulin resistance (HOMA-IR) and fasting insulin were positively correlated with glucose, triglycerides, systolic blood pressure, and diastolic blood pressure, and were negatively correlated with adiponectin (P < 0.05). The 2-h insulin was positively correlated with diastolic blood pressure, triglycerides, and high-sensitivity C-reactive protein. HOMA-IR and fasting insulin remained significantly and positively related to glucose, triglycerides, and blood pressure after adjustment for body composition. The relationships between markers of insulin resistance and adiponectin and high-sensitivity C-reactive protein were attenuated after adjustment for body composition. CONCLUSIONS Surrogate markers of insulin resistance were associated with cardiovascular disease risk factors and inflammation in young, normal-weight, Hispanic women. Our findings suggest that HOMA-IR, fasting, and 2-h insulin may be important clinical markers for identifying young, normal-weight, Hispanic women who may be at risk for development of type 2 diabetes and cardiovascular disease. Our findings show the importance of early screening for prevention of type 2 diabetes and cardiovascular disease in this population.

Physical activity recommendations and cardiovascular disease risk factors in young Hispanic women

Abstract Despite the benefits associated with regular physical activity, there is little epidemiological evidence to support positive health outcomes when meeting physical activity guidelines in high-risk ethnic groups, such as Hispanic women. We compared cardiovascular disease risk factors between young Hispanic women who meet and those who do not meet current physical activity guidelines. Height, weight, waist circumference, and blood pressure were measured in 60 Hispanic women aged 20–39 years. Lipids, C-reactive protein, insulin, and glucose were assessed. Body composition and cardiovascular fitness were assessed by BodPod and maximal oxygen uptake (VO2max) respectively. Participants wore an accelerometer and average minutes (assessed in 10-min bouts) spent in light, moderate, and hard daily activity for weekdays and weekends was determined. Seventy percent of participants did not meet the recommended physical activity guidelines, whereas 30% did so. Following current physical activity guidelines was associated with significantly lower mean cholesterol (mean ± s: 4.2 ± 0.8 vs. 4.7 ± 0.9 mmol · l−1) and triglycerides (0.7 ± 0.3 vs. 1.1 ± 0.6 mmol · l−1), and higher fat-free mass (43.3 ± 3.8 vs. 40.2 ± 5.1 kg) and relative (40.4 ± 7.6 vs. 35.6 ± 7.0 ml · kg−1 · min−1) and absolute (2.5 ± 0.3 vs. 2.1 ± 0.4 litres · min−1) VO2max (P < 0.05). These findings suggest an improved health status in women who meet versus those who did not meet current physical activity guidelines.

Life in the fat lane: seasonal regulation of insulin sensitivity, food intake, and adipose biology in brown bears.

Grizzly bears (Ursus arctos horribilis) have evolved remarkable metabolic adaptations including enormous fat accumulation during the active season followed by fasting during hibernation. However, these fluctuations in body mass do not cause the same harmful effects associated with obesity in humans. To better understand these seasonal transitions, we performed insulin and glucose tolerance tests in captive grizzly bears, characterized the annual profiles of circulating adipokines, and tested the anorectic effects of centrally administered leptin at different times of the year. We also used bear gluteal adipocyte cultures to test insulin and beta-adrenergic sensitivity in vitro. Bears were insulin resistant during hibernation but were sensitive during the spring and fall active periods. Hibernating bears remained euglycemic, possibly due to hyperinsulinemia and hyperglucagonemia. Adipokine concentrations were relatively low throughout the active season but peaked in mid-October prior to hibernation when fat content was greatest. Serum glycerol was highest during hibernation, indicating ongoing lipolysis. Centrally administered leptin reduced food intake in October, but not in August, revealing seasonal variation in the brain’s sensitivity to its anorectic effects. This was supported by strong phosphorylated signal transducer and activator of transcription 3 labeling within the hypothalamus of hibernating bears; labeling virtually disappeared in active bears. Adipocytes collected during hibernation were insulin resistant when cultured with hibernation serum but became sensitive when cultured with active season serum. Heat treatment of active serum blocked much of this action. Clarifying the cellular mechanisms responsible for the physiology of hibernating bears may inform new treatments for metabolic disorders.

A proposed mechanism for exercise attenuated methylglyoxal accumulation: activation of the ARE-Nrf pathway and increased glutathione biosynthesis.

The dicarbonyl methylglyoxal (MGO) is an endogenous metabolite and a known intracellular precursor of advanced glycation endproducts (AGEs). High serum levels of MGO have been correlated with MGO-derived AGEs in individuals with type 2 diabetes (T2DM). Furthermore, there is human and animal evidence to suggest that MGO is causal in copious pathologies related to AGE accumulation including heart disease, hypertension, nephropathy and insulin resistance. MGO is detoxified through the glutathione (GSH) dependent glyoxalase system and diminished glutathione status results in impaired MGO detoxification. Individuals with uncontrolled T2DM have diminished GSH status, suggesting the increase in serum MGO can be partially attributed to impaired MGO detoxification. GSH biosynthesis is heavily dependent upon the antioxidant response element-nuclear respiratory factor pathway (ARE-Nrf) and pharmacological and dietary intervention studies have demonstrated that activation of the ARE-Nrf pathway increases intracellular GSH and glyoxalase enzymes and reduces MGO levels. Acute and chronic exercise has also been shown to increase activation of the ARE-Nrf pathway and GSH biosynthesis, and to improve GSH status. Therefore, we propose that exercise improves MGO detoxification and attenuates MGO accumulation by increasing GSH biosynthesis and improving GSH status through activation of the ARE-Nrf pathway.

Physical activity, cardiorespiratory fitness, and metabolic syndrome in young Mexican and Mexican-American women

Young adult women have had the greatest increase in prevalence of metabolic syndrome (MetS) over time, and prevalence is highest in Hispanic women, compared with women of other ethnicities. Factors contributing to the high prevalence of MetS in Hispanic women are unknown. This study was conducted to determine if physical activity or fitness were associated with individual features of MetS in young Mexican and Mexican-American women, and if the associations were independent of fat mass. Sixty young Mexican and Mexican-American women participated in the study. MetS was defined according to the Adult Treatment Panel III. A fasting blood sample was drawn for the measurement of glucose, insulin, high-density lipoprotein cholesterol (HDL-c), and triglycerides. Physical activity was assessed by questionnaire and accelerometer. Fitness was assessed by progressive treadmill test to exhaustion and ventilatory threshold. Body composition was assessed with Bod Pod. Multivariate regression was used to establish the independent contributions of physical activity and fitness to the individual features of MetS. After controlling for fat mass and fat-free mass, physical activity was found to be independently related to HDL-c and fitness was found to be independently related to triglycerides (p < 0.05). The independent associations between physical activity, fitness, and features of MetS were mediated by, rather than independent of, fat mass. Fat mass was independently related to triglycerides, systolic blood pressure, and diastolic blood pressure. Although physical activity and fitness were related to features of MetS, these associations were not independent of fat mass.

Cardiac response to exercise in normal‐weight and obese, Hispanic men and women: implications for exercise prescription

Aim:  The effects of obesity on cardiac function during incremental exercise to peak oxygen consumption (VO2peak) have not been previously described. The purpose of this study was to compare submaximal and maximal cardiac function during exercise in normal‐weight and obese adults.

Is There a Physiologic Basis for Creatine Use in Children and Adolescents

The purported ergogenic benefits of creatine for the adult population have been well documented. In able-bodied children and adolescents, there is a paucity of data on creatine use and the purported ergogenic effects of creatine. Only 1 study to date has investigated the ergogenic properties of creatine in the adolescent population. The purpose of this review was to try to establish a rationale for creatine use in the child and adolescent population. The limited literature available in this area did not provide a strong enough rationale from either a physiologic or performance perspective for creatine supplementation in these populations. However, significantly more research is required before definitive conclusions can be ade.

Physical Activity and Adiposity-related Inflammation: The MESA

Purpose Physical activity is associated with decreased adiposity-related inflammation in adults. Whether this association is independent of central obesity is unknown but important for understanding the mechanisms associated with reducing cardiometabolic disease risk through physical activity. This study examined whether associations of physical activity and obesity-related inflammatory markers were independent of central adiposity. Methods Between 2002 and 2005, 1970 participants from the Multi-Ethnic Study of Atherosclerosis completed detailed health history and physical activity questionnaires, underwent physical measurements including computed tomography to quantify abdominal visceral and subcutaneous fat, and measurements of adiponectin, leptin, interleukin-6, tumor necrosis factor-alpha, and resistin. Statistical analyses included analysis of covariance and multivariable-adjusted regression. Results The mean (range) age of participants was 64.7 (55–84) yr and 50% were women. After adjustment for age and sex, and compared with the lowest quartile, inflammatory markers in the highest quartile of moderate-to-vigorous physical activity were 16% higher for adiponectin and 30%, 26%, and 9% lower for leptin, interleukin-6, and resistin, respectively (P < 0.05 for all). In linear regression adjusted for demographics, dyslipidemia, hypertension, diabetes, smoking, glomerular filtration rate, renin, and aldosterone, each standard deviation increment of moderate-to-vigorous physical activity was associated with significantly higher levels of adiponectin (&bgr; = 0.04) and lower levels of leptin (&bgr; = −0.06), interleukin-6 (&bgr; = −0.08), and resistin (&bgr; = −0.05, P < 0.05 for all). The associations with leptin, interleukin-6, and resistin were independent of total and central adiposity (P < 0.05), whereas the association between moderate-to-vigorous physical activity and adiponectin was attenuated by central adiposity (P > 0.05). There were no significant interactions by race/ethnicity or sex. Conclusions Moderate-to-vigorous physical activity was associated with a more favorable profile of inflammatory markers, independent of relevant cardiometabolic disease risk factors including central obesity.