Robert W. Lewis

Differences Among Estimates of Critical Power and Anaerobic Work Capacity Derived From Five Mathematical Models and the Three-minute All-out Test

Abstract Bergstrom, HC, Housh, TJ, Zuniga, JM, Traylor, DA, Lewis, RW Jr, Camic, CL, Schmidt, RJ, and Johnson, GO. Differences among estimates of critical power and anaerobic work capacity derived from five mathematical models and the three-minute all-out test. J Strength Cond Res 28(3): 592–600, 2014—Estimates of critical power (CP) and anaerobic work capacity (AWC) from the power output vs. time relationship have been derived from various mathematical models. The purpose of this study was to examine estimates of CP and AWC from the multiple work bout, 2- and 3-parameter models, and those from the 3-minute all-out CP (CP3min) test. Nine college-aged subjects performed a maximal incremental test to determine the peak oxygen consumption rate and the gas exchange threshold. On separate days, each subject completed 4 randomly ordered constant power output rides to exhaustion to estimate CP and AWC from 5 regression models (2 linear, 2 nonlinear, and 1 exponential). During the final visit, CP and AWC were estimated from the CP3min test. The nonlinear 3-parameter (Nonlinear-3) model produced the lowest estimate of CP. The exponential (EXP) model and the CP3min test were not statistically different and produced the highest estimates of CP. Critical power estimated from the Nonlinear-3 model was 14% less than those from the EXP model and the CP3min test and 4–6% less than those from the linear models. Furthermore, the Nonlinear-3 and nonlinear 2-parameter (Nonlinear-2) models produced significantly greater estimates of AWC than did the linear models and CP3min. The current findings suggested that the Nonlinear-3 model may provide estimates of CP and AWC that more accurately reflect the asymptote of the power output vs. time relationship, the demarcation of the heavy and severe exercise intensity domains, and anaerobic capabilities than will the linear models and CP3min test.

Responses during exhaustive exercise at critical power determined from the 3-min all-out test

Abstract The purpose of the present study was to examine oxygen consumption rate ([Vdot] ), heart rate (HR), and ratings of perceived exertion (RPE) responses, as well as time to exhaustion (Tlim) values during continuous rides at critical power (CP) determined from the 3-min all-out test. Eighteen participants (mean ± s: 23.6 ± 3.5 years; 72.7 ± 18.2 kg) performed an incremental cycle ergometer test to exhaustion to determine peak oxygen consumption rate ([Vdot] peak) and HR peak. Critical power was determined from the 3-min all-out test. Metabolic responses ([Vdot] and heart rate), RPE, and Tlim were recorded during continuous rides to exhaustion at CP. Linear regression and t-tests were used to compare [Vdot] , heart rate, and RPE responses during the continuous rides to exhaustion. The Tlim at CP was 12.5 ± 6.5 min. There were significant increases in [Vdot] , HR, and RPE during the continuous rides at CP and 15 of the 18 participants reached [Vdot] peak at exhaustion. Therefore, the [Vdot] , heart rate, and RPE responses, as well as the Tlim values in the present study suggested that CP determined from the 3-min all-out test overestimated the “true” CP and was within the severe exercise intensity domain.

Metabolic and neuromuscular responses at critical power from the 3-min all-out test

The purpose of this study was to determine the specific metabolic and neuromuscular responses at critical power (CP) from the 3-min all-out test. Nine men (mean ± SD: aged 23.7 ± 3.3 years) performed an incremental test for the determination of peak oxygen consumption (VO(2peak)) and gas exchange threshold. CP was estimated for each subject from the 3-min all-out test. Oxygen consumption (VO(2)), the ventilation versus carbon dioxide production ratio (V(E)/VCO(2) ratio), electromyographic (EMG) amplitude, and EMG mean power frequency (MPF) were examined during exhaustive rides at CP for each subject. There was no significant difference between the VO(2) at exhaustion (40.6 ± 7.5 mL·kg(-1)·min(-1)) and VO(2peak) (42.9 ± 7.3 mL·kg(-1)·min(-1)). Furthermore, there were significant increases in EMG amplitude and the V(E)/VCO(2) ratio during the exhaustive rides at CP. There was, however, no significant change in EMG MPF over time. Therefore, the current findings indicated that the 3-min all-out test overestimated CP and the demarcation between the heavy- and severe-intensity domains. Specifically, the VO(2), ventilatory, and EMG amplitude responses were consistent with those observed during continuous exercise in the severe exercise intensity domain. It is likely that the ventilatory and EMG amplitude responses were associated with a common mechanism of fatigue that is different from what affects EMG MPF.

Mechanomyographic and metabolic responses during continuous cycle ergometry at critical power from the 3-min all-out test.

There are limited data regarding metabolic responses during continuous exhaustive rides at critical power (CP) from the 3-min all-out test. In addition, no previous studies have examined the mechanomyographic (MMG) responses at CP from the 3-min all-out test. Therefore, this study examined the metabolic and MMG responses during continuous exercise at CP determined from the 3-min all-out test. Nine college-aged females (mean±SD: age 23.0±3.6yrs) performed an incremental test to exhaustion on a cycle ergometer to identify the gas exchange threshold, peak oxygen consumption rate (V˙O2 peak) and heart rate peak (HR peak). The V˙O2, HR, MMG amplitude and mean power frequency (MPF) responses were examined during continuous rides to exhaustion at CP (81±6% peak power). There were significant increases in V˙O2 and HR over time and there was no significant difference between V˙O2 peak and V˙O2 at exhaustion or HR peak and HR at exhaustion. There were, however, no significant changes for MMG amplitude or MPF over time. Therefore, the current findings suggested that the 3-min all-out test overestimated CP and the demarcation between the heavy and severe intensity domains. Specifically, the V˙O2 and HR responses did not reach a steady state and were driven to peak values. Furthermore, the non-significant change in MMG amplitude and MPF were consistent with the responses observed at fatiguing power outputs (i.e., >80% peak power).

The Rate of Torque Development: A Unique, Non-invasive Indicator of Eccentric-induced Muscle Damage?

This study examined the time courses of recovery for isometric peak torque and rate of torque development (RTD) after eccentric-induced muscle damage. 18 men completed 6 sets of 10 maximal eccentric isokinetic muscle actions at 30° · s(-1). Peak torque, peak RTD and RTD at 10 (RTD10), 50 (RTD50), 100 (RTD100) and 200 ms (RTD200), serum creatine kinase and lactate dehydrogenase were measured before (PRE), immediately after (POST), 24, 48 and 72 h after eccentric exercise. Creatine kinase and lactate dehydrogenase increased from 139 to 6 457 and from 116 to 199 IU · L(-1) from PRE to 72 h, respectively. Peak torque and all RTDs decreased at POST. Peak torque and RTD200 remained lower than PRE through 72 h. Peak RTD remained lower than PRE through 48 h, but was not different from PRE at 72 h. RTD10 and RTD100 were lower than PRE through 24 h, but were not different from PRE at 48 and 72 h. RTD50 decreased at POST, but was not different from PRE at 24 h. Early phase RTDs recovered more quickly than PT and RTD200. Early phase RTDs may reflect neural mechanisms underlying eccentric-induced force decrements, while late RTDs may describe the same physiological mechanisms as PT.

Physiologic responses to a thermogenic nutritional supplement at rest, during low-intensity exercise, and during recovery from exercise in college-aged women.

This study examined acute physiologic responses to a thermogenic nutritional supplement at rest, during exercise, and during recovery from exercise in women. Twelve women (mean ± SD age, 22.9 ± 3.1 years) were recruited for this randomized, double-blinded, placebo-controlled, crossover study. Each testing session consisted of 4 phases: 30 min of presupplementation resting, followed by the ingestion of the placebo or thermogenic nutritional supplement; 50 min of postsupplementation resting; 60 min of walking (at 3.2-4.8 km·h(-1)); and 50 min of postexercise resting. Energy expenditure (EE), oxygen consumption, respiratory exchange ratio (RER), oxygen (O2) pulse, and heart rate (HR) values were recorded during all 4 phases. Systolic (SBP) and diastolic (DBP) blood pressure were recorded during the rest, postsupplementation, and postexercise recovery phases; ratings of perceived exertion (RPE) were recorded only during exercise. There were no significant differences for EE, oxygen consumption, O2 pulse, HR, SBP, or DBP between the supplement and placebo during the presupplementation resting or postsupplementation phases. The RER, however, was higher with the supplement at 30 min postsupplementation. During exercise, EE and O2 pulse were 3%-6% greater with the supplement than placebo; there were no significant differences in RPE. Postexercise, EE, oxygen consumption, and DBP were 3%-7% greater with the supplement than placebo. These findings suggest that a thermogenic nutritional supplement, when combined with exercise, increases metabolic rate but has no effect on the perception of effort and results in only minimal changes in cardiovascular function.

Metabolic, cardiovascular, and perceptual responses to a thermogenic nutritional supplement at rest, during exercise, and recovery in men.

Abstract Bergstrom, HC, Housh, TJ, Traylor, DA, Lewis, Jr RW, Cochrane, KC, Jenkins, NDM, Schmidt, RJ, Johnson, GO, Housh, DJ, and Cramer, JT. Metabolic, cardiovascular, and perceptual responses to a thermogenic nutritional supplement at rest, during exercise, and recovery in men. J Strength Cond Res 28(8): 2154–2163, 2014—Twenty-one men (mean ± SD; age = 23.5 ± 2.6 years, BMI = 26.0 ± 2.4 kg·m−2) completed this randomized, double-blinded, placebo-controlled, crossover study to examine acute responses to a thermogenic nutritional supplement. Each testing session included: (a) 30 minutes resting, followed by placebo or thermogenic nutritional supplementation, (b) 50 minutes postsupplementation resting, (c) 60 minutes walking, and (d) 50 minutes postexercise recovery. Gas exchange variables and heart rate (HR) were recorded during each phase. Blood pressure was recorded during all phases except exercise. Ratings of perceived exertion (RPE) were recorded only during exercise. There were no significant differences for any of the measures between the supplement and placebo during the initial resting or postsupplementation phases. During exercise, energy expenditure (EE) (placebo = 18.98–19.06 kJ·min−1 and supplement = 19.44–19.82 kJ·min−1) and V[Combining Dot Above]O2 (placebo = 11.27–11.35 ml·kg−1·min−1; supplement = 11.64–11.82 ml·kg−1·min−1) were greater for the supplement than placebo. There were no differences in respiratory exchange ratio (RER), HR, or RPE between the supplement and placebo during exercise. Postexercise, only V[Combining Dot Above]O2 (placebo = 3.53–3.63 ml·kg−1·min−1; supplement = 3.71–3.84 ml·kg−1·min−1) was greater for the supplement than placebo, but there were no differences in EE, RER, HR, or blood pressure. These findings suggested that the specific blend of ingredients in the thermogenic nutritional supplement, when combined with exercise, increased the metabolic rate with minimal changes in cardiovascular function and no effect on RPE.

The effects of gender and very short-term resistance training on peak torque, average power and neuromuscular responses of the forearm flexors

OBJECTIVE: This study examined the effects of sex on peak torque (PT), average power (AP), and the time (AMP) and frequency (MPF) domain parameters of the electromyographic (EMG) and mechanomyographic (MMG) signals following very short-term resistance training (VST) of the forearm flexors. Based on the results of previous studies it was hypothesized that three training sessions would increase PT, EMG MPF, and MMG MPF of the forearm flexors at 60 and 180 ◦ /s in men only, without changes to AP, EMG AMP, or MMG AMP for either men or women. METHODS: Nine men and nine women completed two pretests, three training sessions, and a posttest that included concentric isokinetic muscle actions of the forearm flexors at 60 and 180 ◦ /s. The AMP and MPF of the EMG and MMG signals were recorded from the biceps brachii. RESULTS: The results indicate increases in PT, AP, and MMG AMP at 60 and 180 ◦ /s for the men only, but no changes in EMG AMP, EMG MPF, or MMG MPF for either the men or women. CONCLUSION: There were gender differences in the PT and AP responses to VST of the forearm flexors that were not associated with increased agonist muscle activation. These findings have implications for the development of gender-specific VST programs for the forearm flexors in clinical settings.

Dissociations Among Direct and Indirect Indicators of Adiposity in Young Wrestlers

Abstract Cochrane, KC, Housh, TJ, Bergstrom, HC, Jenkins, NDM, Johnson, GO, Housh, DJ, Traylor, DA, Lewis, RW Jr, Schmidt, RJ, and Cramer, JT. Dissociations among direct and indirect indicators of adiposity in young wrestlers. J Strength Cond Res 29(2): 408–415, 2015—The purposes of this study were to: (a) examine the age-related patterns of differences in height (HT), body mass (BM), percent body fat (% fat), body mass index (BMI), and skinfolds (SF) in 11- to 18-year-old wrestlers; (b) determine the coherence of direct (% fat) and indirect (BMI and SFs) indicators of adiposity in the wrestlers; and (c) compare the age-related patterns and mean values for HT, BM, BMI, subscapular, and triceps SF for the wrestlers to those of national samples of boys from the National Health and Nutrition Examination Survey (NHANES) database. One hundred thirty wrestlers were divided into 8 independent yearly age groups (AG): AG11–AG18 years. Height, BM, BMI, subscapular SF, triceps SF, medial calf SF, thigh SF, sum of SFs, and % fat were assessed. There were no differences between the wrestlers and NHANES samples for age-related patterns of BMI (0.61 and 0.63 kg·m−2·y−1), subscapular SF (0.47 and 0.37 mm·y−1), or triceps SF (−0.31 and −0.39 mm·y−1). Furthermore, the wrestlers displayed no differences in % fat between age groups. The results indicated that: (a) dissociations existed between the direct and indirect indicators of adiposity; (b) the wrestlers were similar in height but had smaller upper-body SFs when compared with NHANES samples; and (c) participation in wrestling (1–8 years) had no adverse effects on the normal age-related growth patterns for HT, but favorable effects on measures of adiposity.

Age and isokinetic peak torque at the elbow in young girl swimmers

OBJECTIVE: This cross-sectional study examined the relationships between age and absolute peak torque (PT) as well as PT covaried for body weight (BW), height (HT), and/or fat-free weight (FFW) in young girl swimmers. METHODS: Twenty-nine girl swimmers (age = 12.4 ± 1.9 yr) were measured for isokinetic elbow flexion and extension PT at 30, 180, 300 ◦ · s −1 , as well as BW, HT, and FFW. Zero-order correlations as well as first, second, and third-order partial correlations were used to determine the relationships for age versus PT and age versus PT covaried for BW, HT, and/or FFW. RESULTS:There were age-related increases for all absolute PT measures (r = 0.47 to 0.77), except elbow flexion at 300 ◦ · s −1 . For all but one of the measures (forearm extension at 30 ◦ · s −1 ; r = 0.42 to 0.56), the increases in PT were accounted for by changes in BW, HT, and/or FFW. CONCLUSION: The results of this study indicated that agef-related increases in PT for four of the six measures were accounted for by BW, HT, and/or FFW. The age-related increases in PT for elbow flexion at 30 ◦ · s −1 independent of BW, HT, and/or FFW,