Vascular limitations in blood pressure regulation with age in women: Insights from exercise and acute cardioselective ß-blockade.

Younger women rely on altering cardiac output ( Q ̇ $\dot{Q}$ ) to regulate blood pressure (BP). In contrast, older women rely more on altering vascular tone. However, evidence suggests that the ability to alter systemic vascular conductance (SVC) is diminished in older women. In the present study, cardioselective ß-blockade was utilized to diminish the relative contribution of Q ̇ $\dot{Q}$ to BP regulation and thereby evaluate age-related vascular limitations in women at rest and during large muscle dynamic exercise. Younger (n = 13, mean age 26.0 years) and older (n = 14, mean age 61.8 years) healthy women performed submaximal bouts of semi-recumbent cycling exercise at varying intensities while receiving an intravenous infusion of esmolol, a ß1-antagonist, or saline control in a repeated-measures crossover design. Q ̇ $\dot{Q}$ was attenuated during esmolol infusion, with greater reductions during exercise (moderate, -1.0 (95% CI, -1.6 to -0.5) L/min, P < 0.001; heavy, -2.0 (95% CI, -2.6 to -1.5) L/min, P < 0.001) than seated rest (-0.5 (95% CI, -1.1 to 0.0) L/min, P = 0.048), and this reduction was not significantly different between age groups (P = 0.122). Older women exhibited a greater attenuation in mean arterial pressure (MAP) during esmolol (-7 (95% CI, -9 to -4) mmHg, P < 0.001) relative to younger women (-2 (95% CI, -5 to 0) mmHg, P = 0.071). These changes coincided with a greater reduction of SVC in the younger women during esmolol (-15 (95% CI, -20 to -10) mL/min/mmHg, P < 0.001) compared to older women (-3 (95% CI, -9 to 2) mL/min/mmHg, P = 0.242). Together, these findings provide evidence that older, postmenopausal women have a diminished ability to adjust SVC in order to regulate MAP.

Inorganic nitrate supplementation and blood flow restricted exercise tolerance in post-menopausal women.

Exercise tolerance appears to benefit most from dietary nitrate (NO3-) supplementation when muscle oxygen (O2) availability is low. Using a double-blind, randomized cross-over design, we tested the hypothesis that acute NO3- supplementation would improve blood flow restricted exercise duration in post-menopausal women, a population with reduced endogenous nitric oxide bioavailability. Thirteen women (57-76 yr) performed rhythmic isometric handgrip contractions (10% MVC, 30 per min) during progressive forearm blood flow restriction (upper arm cuff gradually inflated 20 mmHg each min) on three study visits, with 7-10 days between visits. Approximately one week following the first (familiarization) visit, participants consumed 140 ml of NO3- concentrated (9.7 mmol, 0.6 gm NO3-) or NO3-depleted beetroot juice (placebo) on separate days (≥7 days apart), with handgrip exercise beginning 100 min post-consumption. Handgrip force recordings were analyzed to determine if NO3- supplementation enhanced force development as blood flow restriction progressed. Nitrate supplementation increased plasma NO3- (16.2-fold) and NO2- (4.2-fold) and time to volitional fatigue (61.8 ± 56.5 s longer duration vs. placebo visit; p = 0.03). Nitrate supplementation increased the rate of force development as forearm muscle ischemia progressed (p = 0.023 between 50 and 75% of time to fatigue) with non-significant effects thereafter (p = 0.052). No effects of nitrate supplementation were observed for mean duration of contraction or relaxation rates (all p > 0.150). These results suggest that acute NO3- supplementation prolongs time-to-fatigue and speeds grip force development during progressive forearm muscle ischemia in postmenopausal women.

Comparison of Energy Expenditure During Single-Set vs. Multiple-Set Resistance Exercise.

The purpose of this study was to compare energy expenditure (EE) of single-set and multiple-set resistance exercise protocols using indirect calorimetry. Twelve men and twelve women (age = 21.4 ± 1.3 years) performed a single-set (SS) and multiple-set (MS) resistance exercise protocol in random order. The subjects performed two protocols at 70% of their 1-repetition maximum. The protocols consisted of 5 upper-body exercises of either 1 or 3 sets per exercise performed in random order. Metabolic and cardiorespiratory data were recorded over the entire exercise session and during 5 minutes of recovery by a portable metabolic measurement system. Gross (167.9 ± 58.7 kcal) and net (88.3 ± 41.6 kcal) EE for the MS protocol were significantly greater (p < 0.001) than gross (71.3 ± 26.5 kcal) and net (36.3 ± 18.7 kcal) EE of the SS protocol. Conversely, there was no significant difference in the rate of EE between both protocols. Significant gender differences (p < 0.001) in absolute and relative EE were observed for both protocols where values in men were higher than women. Heart rate, respiratory rate, relative V[Combining Dot Above]O2, respiratory exchange ratio, and minute ventilation values were significantly higher during the MS than the SS protocol. The results of this study indicated that MS protocols yield greater metabolic and cardiovascular demands than SS protocols when the number of exercises performed is the same.

Electromyographic analysis of muscle activation during sit-and-reach flexibility tests.

The sit-and-reach test (SRT) has been included in standard fitness test batteries for decades, but empirical evidence of actual muscle activity has been lacking. Furthermore, the positioning of the ankle joint during the execution of this test has received relatively scant attention. Therefore, the purpose of this investigation was to compare surface electromyographic (sEMG) activity of selected lower extremity and back musculature and examine the impact of ankle positioning during the standard SRT and the modified sit-and-reach test (MSRT). Seven male and 7 female subjects performed 3 trials of the SRT and MSRT, each in a dorsiflexed and plantar flexed ankle position. During all trials, muscle activity (sEMG) was measured from the right semimembranous (SM), erector spinae (ES), and gastrocnemius (G). Mean sEMG data from each muscle (SM, ES, and G) were normalized by being expressed as a percent contribution to the total electrical activity (100%). Surface electromyographic activity data were also used to determine muscle activation ratios (e.g., SM to ES). Results revealed significantly higher flexibility scores during the plantar flexion condition for both test modalities. The SM exhibited the greatest percent contribution to total sEMG activity within all testing conditions. The SM to G and SM to ES muscle activation ratios were significantly greater than their inverse counterparts within all 4 testing conditions. Based on the 2 sEMG analysis techniques, the SM seemed to exhibit the greatest muscle activity. This investigation provides direct evidence of sEMG muscle activity during the SRT and MSRT, further confirming these tests to be a valid measure of hamstring flexibility.

Bilateral NIRS measurements of muscle mitochondrial capacity: Feasibility and repeatability.

BACKGROUND: Non-invasive determination of mitochondrial capacity via near infrared spectroscopy (NIRS) typically involves voluntary exercise of a single muscle group followed by as many as 26 brief ischemic cuff occlusions to determine a single recovery rate constant (k). PURPOSE: To determine the within- and between-visit repeatability of a shortened bilateral NIRS protocol, and to establish the feasibility of hamstring k measurements. METHODS: Sixteen young (eight women, eight men; 22 ± 3 years) active adults underwent a bilateral electrical stimulation protocol in which multiple (n = 4) measurements of k for the vastus lateralis (VL) and medial hamstring (MH) muscles were determined on two visits. Repeatability (CV% and intraclass correlations, ICC) and equivalency across visits were assessed for both muscles. RESULTS: Mean k values in the VL were consistent with published values and within-visit ICCs were moderately high for both muscles in both sexes. In men, average k values on visit 2 were within 1% (VL muscle) and 5% (MH muscle) of the values on visit 1 (all p > 0.78). In women, average k values were 10%-15% lower on visit 2 (p = 0.01 and p = 0.15 for MH and VL) with the largest between-visit differences in a subset of participants with the most days between visits. CONCLUSIONS: This bilateral NIRS protocol is time efficient and provides valid estimates of k in both sexes and muscle groups with acceptable within-visit repeatability. Lower than expected between-visit repeatability in some participants reinforces the need for further investigation of this newly developed protocol to identify and control for experimental and behavioral sources of variation.

Cerebral oxygenation declines at exercise intensities above the respiratory compensation threshold.

During incremental exercise PaCO2 and PETCO2 begin to decline at the respiratory compensation threshold (RCT-GEX). Since PaCO2 alters cerebral blood flow it was hypothesized that there would be a systematic decline in cerebral oxygenation (Cox) measured by near infrared spectroscopy above the RCT (RCT-NIRS). Cardiorespiratory and NIRS responses were simultaneously monitored from the left frontal lobe during incremental exercise in 17 men. All subjects showed a decline in Cox above the RCT-GEX with a 20-40 s delay. Significant differences (P<0.01) were observed between the RCT-GEX and RCT-NIRS for time (9.83 versus 10.39 min), power (198 versus 212 W) and oxygen uptake (2.31 versus 2.43 L min-1). Intra-class correlations for power and absolute VO2 were 0.97 and 0.98, respectively. Bland-Altman analysis revealed no outliers for any of the variables. The results suggested that the decrease in Cox observed above the RCT was most likely due to a reduction in cerebral blood flow mediated by a decline in PaCO2. This decline in Cox could reduce neuronal activation thereby limiting maximal exercise capacity in healthy subjects.

Anthropometric profiles and social physique anxiety of physical education professionals from India.

Previous work indicates that there may be a relationship between the observation and evaluation of one's physique and the construct of social physique anxiety associated with this process. Since physical educators are expected to serve as role models of desired fitness behaviors, bodily appearance, and composition, it is of interest to examine whether such responses and relationships may be observed. However, there is limited published information on anthropometric profiles and body images of physical education professionals, especially of those from India. Therefore, this study compared anthropometric profiles and Social Physique Anxiety in a sample of 182 male physical education professionals from India (M age=41.2 yr.). Body Mass Index, sum of three skinfolds (Tricep, Abdomen, and Thigh), and waist/hip ratio were determined using standard procedures. The sample was grouped into overweight and normal weight categories. Significant group differences were found for the sum of skinfolds and waist/hip ratio, with no significant differences between groups on the Social Physique Anxiety total score. Correlations for the anthropometric measures with the Social Physique Anxiety scores indicated no significant relationships. Mean total Social Physique Anxiety score for the combined group was comparable to those reported for other groups of physically active individuals. These findings indicate low Social Physique Anxiety in this sample and may have implications with regard to the attitudes pertaining to body image and role modeling of appropriate fitness behaviors.

Validation of an equation for predicting energy cost of arm ergometry in women.

Few studies have examined the validity of metabolic equations for the prediction of energy cost (VO(2)) of arm ergometry in women. Therefore, the purpose of this study was (a) to compare directly measured and predicted VO(2) values using the American College of Sports Medicine (ACSM) equation and (b) to develop and validate a prediction equation for women. A sample of 60 female subjects with mean (+/-SD) age, weight and height 26.5 +/- 14.4 years, 61.5 +/- 7.6 kg, 163.3 +/- 6.0 cm, respectively, was randomly assigned to an equation group (N = 40) and a cross validation group (N = 20). All subjects performed an incremental arm ergometry test (10 W increases every 2 min), until termination criteria were met. Repeated measures ANOVA indicated significant differences between the measured VO(2) and ACSM predicted VO(2) during all the incremental test work rate. Multiple linear regression analysis was used to develop the following upper body exercise VO(2) prediction equation: VO(2)(ml . kg(-1) . min(-1) = 23.461 - (0.272 x Body Weight) + (0.403 x watts) [R(2) = 0.82, SEE = 2.79] Cross validation indicated lower variability using the current prediction equation. An additional independent sample of 13 subjects performed a 30-min steady-state test at 40% of their pre-determined maximal work rate. VO(2) measured during the 30 min steady-state test (was significantly different P < 0.05) from the ACSM prediction at all time intervals. There were no significant differences using the above equation following the 5 min time interval. Therefore, a new equation is proposed as a means of providing a gender-specific energy cost prediction equation.