Michael J. Webster

Effects of Aerobic Exercise on Anxiety Sensitivity

Anxiety sensitivity is a known precursor to panic attacks and panic disorder, and involves the misinterpretation of anxiety-related sensations. Aerobic exercise has been shown to reduce generalized anxiety, and may also reduce anxiety sensitivity through exposure to feared physiological sensations. Accordingly, 54 participants with elevated anxiety sensitivity scores completed six 20-min treadmill exercise sessions at either a high-intensity aerobic ( n = 29 ) or low-intensity ( n = 25 ) level. Self-ratings of anxiety sensitivity, fear of physiological sensations associated with anxiety, and generalized anxiety were obtained at pre-treatment, post-treatment, and one-week follow-up. Results indicated that both high- and low-intensity exercise reduced anxiety sensitivity. However, high-intensity exercise caused more rapid reductions in a global measure of anxiety sensitivity and produced more treatment responders than low-intensity exercise. Only high-intensity exercise reduced fear of anxiety-related bodily sensations. The implications of these findings are discussed.

Comparison of glycerol and water hydration regimens on tennis-related performance.

PURPOSE To compare glycerol and water hyperhydration and rehydration on tennis related skill and agility performance. METHODS Eleven male subjects completed two counter-balanced, double-blind trials. Each trial consisted of three phases: 1). hyperhydration with or without glycerol (1.0 g.kg/(-1)) over 150 min, 2). 120 min of exercise-induced dehydration (EID), and 3) rehydration with or without glycerol (0.5 g.kg(-1)) over 90 min. After each phase, subjects performed 5- and 10-m sprint tests, a repeated-effort agility test, and tennis skill tests. RESULTS Glycerol (G) hyperhydration significantly increased fluid retention by approximately 900 mL over the placebo (P) (P<or= 0.05). After EID, body weight was reduced in both groups but was not significantly different between groups (G: -2.71 +/- 0.08, P: -2.67 +/- 0.09%). At the end of the rehydration phase, PV was significantly greater in the G trial than in the P trial, and the G trial resulted in a significantly greater fluid retention of approximately 700 mL over the P trial ( P<or= 0.05). Although the magnitude of hypohydration was modest (<3%), sprint times were significantly slower after the EID ( P<or= 0.05) compared with post hyperhydration and post rehydration but were not significantly different between trials. No significant difference existed between groups and across time for the repeated effort agility tests and groundstrokes and serve tests. CONCLUSION The data demonstrate that relatively modest hypohydration ( approximately 2.7%) as a result of EID, significantly slows 5- and 10-m sprint times. Furthermore, although the glycerol hydration regimen provided a better hydration status than the placebo hydration regimen, no performance benefits were observed.

Effect of moderate dehydration on torque, electromyography, and mechanomyography

The purpose of the present investigation was to test the hypotheses that the mechanomyographic (MMG) signal would be affected by hydration status due to changes in the intra‐ and extracellular fluid content (which could affect the degree of fluid turbulence), changes in the filtering properties of the tissues between the MMG sensor and muscle, and changes in torque production that may accompany dehydration. Ten subjects (age 22.5 ± 1.6 years) were tested for maximal isometric (MVC), submaximal isometric (25, 50, and 75%MVC), and maximal concentric isokinetic muscle strength of the biceps brachii in either a euhydrated or dehydrated state while the electromyographic (EMG) and MMG signals were recorded. Separate three‐way and two‐way ANOVAs indicated no change in torque, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF with dehydration. The lack of dehydration effect suggests that MMG may be more reflective of the intrinsic contractile processes of a muscle fiber (torque production) or the motor control mechanisms (reflected by the EMG) than the tissues and fluids surrounding the muscle fiber.

Physiological and performance responses to supplementation with thiamin and pantothenic acid derivatives

Abstract The purpose of this study was to investigate the physiological and performance responses to supplementation with allithiamin and pantethine. On two separate occasions, six highly trained cyclists [maximum O2 consumption or V˙O2max 61.8 (2.1) ml · kg−1 · min−1] performed a 50-km steady-state ride on a cycle ergometer at a workload corresponding to ∼60% of V˙O2max followed by a 2000-m time trial. For 7 days prior to each ride, subjects daily ingested either a placebo (PL) or a combination of 1 g of allithiamin and 1.8 g of a 55%/45% pantethine/pantothenic acid compound (AP). Treatments were administered using a randomized, double-blind, counter-balanced design. During the 50-km ride, measures of heart rate, respiratory gas exchange and ratings of perceived exertion were recorded at 5, 15, 25, 35 and 45 km. Blood samples were collected at 10, 20, 30, 40 and 50 km and analyzed for lactate, glucose and free fatty acids. Blood samples for the analysis of lactate were also collected 3 and 5 min after the completion of the 2000-m time trial. There were no significant differences in any of the measured parameters between experimental conditions. Time to complete the 2000-m time trial was also not significantly different between experimental conditions [PL 178.2 (8.4), AP 170.7 (10.2) s; P = 0.58]. These results suggest that, despite the reported enhanced absorption properties, supplementation with allithiamin and pantethine does not alter exercise metabolism or exercise performance.

Running economy and maximal oxygen consumption after 4 weeks of oral Echinacea supplementation.

Abstract Whitehead, MT, Martin, TD, Scheett, TP, and Webster, MJ. Running economy and maximal oxygen consumption after 4 weeks of oral Echinacea supplementation. J Strength Cond Res 26(7): 1928–1933, 2012—The purpose of this investigation was to determine the effects of 4 weeks of oral Echinacea (ECH) supplementation on erythropoietin (EPO), red blood cell (RBC) count, running economy (RE), and V[Combining Dot Above]O2max. Twenty-four men aged 24.9 ± 4.2 years, height 178.9 ± 7.9 cm, weight 87.9 ± 14.6 kg, body fat 19.3 ± 6.5% were grouped using a double-blind design and self-administered an 8,000-mg·d−1 dosage of either ECH or placebo (PLA) in 5 × 400 mg × 4 times per day for 28 days. Blood samples were collected and analyzed for RBCs and EPO using automated flow cytometery and enzyme-linked immunosorbent assay. Maximal graded exercise tests (GXTs) were administered to measure V[Combining Dot Above]O2max, RE, and heart-rate responses. Analysis of variance was used to determine statistically significant differences (P ⩽ 0.05). The EPO increased significantly in ECH at 7 days (ECH: 15.75 ± 0.64, PLA: 10.01 ± 0.73 mU·ml−1), 14 days (ECH: 18.88 ± 0.71, PLA: 11.02 ± 0.69 mU·ml−1), and 21 days (ECH: 16.06 ± 0.55, PLA: 9.20 ± 0.55 mU·ml−1). V[Combining Dot Above]O2max increased significantly in ECH (ECH: 1.47 ± 1.28, PLA: −0.13 ± 0.52%). Running economy improved significantly in ECH as indicated by a decrease in submaximal V[Combining Dot Above]O2 during the first 2 stages of the GXT (stage 1: ECH −1.50 ± 1.21, PLA 0.60 ± 1.95%; stage 2: ECH −1.67 ± 1.43, PLA 0.01 ± 1.03%). These data suggest that ECH supplementation results in significant increases in EPO, V[Combining Dot Above]O2max, and running economy.

Several steps/day indicators predict changes in anthropometric outcomes: HUB City Steps

BackgroundWalking for exercise remains the most frequently reported leisure-time activity, likely because it is simple, inexpensive, and easily incorporated into most people’s lifestyle. Pedometers are simple, convenient, and economical tools that can be used to quantify step-determined physical activity. Few studies have attempted to define the direct relationship between dynamic changes in pedometer-determined steps/day and changes in anthropometric and clinical outcomes. Hence, the objective of this secondary analysis was to evaluate the utility of several descriptive indicators of pedometer-determined steps/day for predicting changes in anthropometric and clinical outcomes using data from a community-based walking intervention, HUB City Steps, conducted in a southern, African American population. A secondary aim was to evaluate whether treating steps/day data for implausible values affected the ability of these data to predict intervention-induced changes in clinical and anthropometric outcomes.MethodsThe data used in this secondary analysis were collected in 2010 from 269 participants in a six-month walking intervention targeting a reduction in blood pressure. Throughout the intervention, participants submitted weekly steps/day diaries based on pedometer self-monitoring. Changes (six-month minus baseline) in anthropometric (body mass index, waist circumference, percent body fat [%BF], fat mass) and clinical (blood pressure, lipids, glucose) outcomes were evaluated. Associations between steps/day indicators and changes in anthropometric and clinical outcomes were assessed using bivariate tests and multivariable linear regression analysis which controlled for demographic and baseline covariates.ResultsSignificant negative bivariate associations were observed between steps/day indicators and the majority of anthropometric and clinical outcome changes (r = -0.3 to -0.2: P < 0.05). After controlling for covariates in the regression analysis, only the relationships between steps/day indicators and changes in anthropometric (not clinical) outcomes remained significant. For example, a 1,000 steps/day increase in intervention mean steps/day resulted in a 0.1% decrease in %BF. Results for the three pedometer datasets (full, truncated, and excluded) were similar and yielded few meaningful differences in interpretation of the findings.ConclusionsSeveral descriptive indicators of steps/day may be useful for predicting anthropometric outcome changes. Further, manipulating steps/day data to address implausible values has little overall effect on the ability to predict these anthropometric changes.

Effect of six weeks of oral echinacea purpurea supplementation on nitric oxide production

Background Echinacea purpurea, a purple coneflower plant of the compositae family (Asteraceae), is native to North America and commonly used as an herbal supplement to enhance immune function. Echinacea purpurea has been shown to stimulate macrophage activity which is a known stimulator of nitric oxide (NO) production. Echinacea purpurea supplementation (8,000 mg·d) in untrained (42.5 ± 1.6 mL·kg·min) males was shown to elicit a 63% increase (p < 0.05) in serum erythropoietin (EPO) following two weeks of supplementation. This is supported in part by earlier findings which indicated that four weeks of Echinacea purpurea supplementation demonstrated a non-significant increase in maximal oxygen uptake (VO2max). It is plausible that Echinaceainduced EPO production may stimulate physiological responses independent of and/or in addition to erythropoiesis. There is also evidence suggesting EPO has vasculo-protective effects including the activation of endothelial nitric oxide synthase (eNOS). Based on these findings, a proposed non-hematological response to the Echinacea-induced increase in EPO could be enhanced NO production. The purpose of this investigation was to determine whether six weeks of oral Echinacea purpurea supplementation augmented NO production as a result of an Echinacea-induced increase in EPO and/or Echinaceainduced macrophage activity.

The effect of glycerol on torque, electromyography, and mechanomyography.

The purpose of this investigation was to determine the effect of hyperhydration on the electromyographic (EMG) and mechanomyographic (MMG) responses during isometric and isokinetic muscle actions of the biceps brachii. Eight (22.1 ± 1.8 years, 79.5 ± 22.8 kg) subjects were tested for maximal isometric, submaximal isometric, and maximal concentric isokinetic muscle strength in either a control (C) or hyperhydrated (H) state induced by glycerol ingestion while the EMG and MMG signals were recorded. Although fluid retention was significantly greater during the H protocol, the analyses indicated no change in torque, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, or MMG MPF with hyper-hydration. These results indicated that glycerol-induced fluid retention does not affect the torque-producing capabilities of a muscle, the impulses (EMG) going to a muscle, or muscular vibrations (MMG). It has been suggested that EMG and MMG can be used as direct electrical/mechanical monitoring, which could be presented to trainers and athletes; however, before determining the utility of these signals, the MMG and EMG responses should be examined under a variety of conditions such as in the present study.

A pilot study on the effect of oral contraceptives on electromyography and mechanomyography during isometric muscle actions

The purpose of this pilot study was to determine the influence of oral contraceptives (OC) on electromyography (EMG) and mechanomyography (MMG) during isometric (ISO) muscle actions of the rectus femoris. Two groups of women (Mean +/- SEM, 24 +/- 1 yrs, 1.68 +/- 0.02 m, 70.97 +/- 4.81 kg) were recruited and tested five times throughout one complete menstrual cycle. The first group (n=7) were not taking hormonal treatment (NOC) and the OC group (n=6) had been taking exogenous hormones for at least six months prior. Each participant performed maximal ISO muscle actions (MVC) of the leg extensors on a Cybex II isokinetic dynamometer followed by randomly assigned sub-maximal ISO muscle actions. Bipolar surface EMG electrodes were placed over the rectus femoris with a piezoelectric MMG recording device placed between the two electrodes. Three separate three way (group x day x %MVC) mixed factorial repeated measures ANOVAs were used to determine differences in torque, EMG and MMG between NOC and OC subjects. There were no significant three-way interactions involving group for normalized torque, EMG or MMG. These results indicated that OC does not have an effect on torque, EMG or MMG during ISO muscle actions of the rectus femoris.

Examination of Effects of Oral Contraceptive Use on Electromyography and Mechanomyography Findings During Muscle Fatigue of the Rectus Femoris

Background: Female athletes are reported to be at an increased risk for anterior cruciate ligament (ACL) injuries compared to male athletes. Fatigue may play a role in the occurrence of ACL injuries due to changes in dynamic stability of the knee. Purpose: To determine changes in muscle function across the menstrual cycle for women not using oral contraceptive (NOC) and women using oral contraceptives (OC) during concentric (CON) and eccentric (ECC) isotonic muscle fatigue actions. Study Design: Prospective quasi‐experimental cohort design. Methods: Fourteen healthy, physically active women (Mean ± SEM, 23 ± 1 yrs, 1.7 ± 1 m, 60 ± 2 kg) were recruited and tested 3 times throughout one complete menstrual cycle. The NOC group (N = 6) was not taking any form of hormonal treatment and all had normal menstrual cycles lasting between 26 and 32 days. The second group (N = 8) had been taking OC for at least 6 months. Each participant performed one maximal isotonic strength (1‐RM) test of the leg extensors. For each of the 3 testing sessions, each participant performed a fatigue protocol at 50% of 1‐RM. Bipolar surface EMG electrodes were placed mid‐thigh over the rectus femoris with a piezoelectric MMG recording device placed between the two electrodes. Results: No significant 2‐way interactions for number of repetitions performed on each day, CON EMG, ECC EMG, CON MMG, or ECC MMG during fatigue. Conclusions: Based on the results from our sample population, no evidence was found to support the hypotheses of differences in muscle function between NOC and OC females.