Haley C. Bergstrom

A new single work bout test to estimate critical power and anaerobic work capacity

Bergstrom, HC, Housh, TJ, Zuniga, JM, Camic, CL, Traylor, DA, Schmidt, RJ, and Johnson, GO. A new single work bout test to estimate critical power and anaerobic work capacity. J Strength Cond Res 26(3): 656–663, 2012—The purpose of this study was to develop a 3-minute, all-out test protocol using the Monark cycle ergometer for estimating the critical power (CP) and anaerobic work capacity (AWC) with the resistance based on body weight. Twelve moderately trained adults (mean age ± SD = 23.2 ± 3.5 years) performed an incremental cycle ergometer test to exhaustion. The CP and AWC were estimated from the original work limit (Wlim) vs. time limit (Tlim) relationship (CPPT) and a 3-minute all-out test (CP3min) against a fixed resistance and compared with the CP and AWC estimated from the new 3-minute tests on the Monark cycle ergometer (CP3.5% and CP4.5%). The resistance values for the CP3.5% and CP4.5% tests were set at 3.5 and 4.5% of the subjects body weight (kilograms). The results indicated that there were no significant differences (p > 0.05) among mean CP values for CPPT (178 ± 47 W), CP3.5% (173 ± 40 W), and CP4.5% (186 ± 44 W). The mean CP3min (193 ± 54 W), however, was significantly greater than CPPT and CP3.5%. There were no significant differences in AWC for the CPPT (13,412 ± 6,247 J), CP3min (10,895 ± 2,923 J), and CP4.5% (9,842 ± 4,394 J). The AWC values for the CPPT and CP3min, however, were significantly greater than CP3.5% (8,357 ± 2,946 J). The results of this study indicated that CP and AWC could be estimated from a single 3-minute work bout test on the Monark cycle ergometer with the resistance set at 4.5% of the body weight. A single work bout test with the resistance based on the individuals body weight provides a practical and accessible method to estimate CP and AWC.

Neuromuscular Adaptations After 2 and 4 Weeks of 80% Versus 30% 1 Repetition Maximum Resistance Training to Failure.

Abstract Jenkins, NDM, Housh, TJ, Buckner, SL, Bergstrom, HC, Cochrane, KC, Hill, EC, Smith, CM, Schmidt, RJ, Johnson, GO, and Cramer, JT. Neuromuscular adaptations after 2 and 4 weeks of 80% versus 30% 1 repetition maximum resistance training to failure. J Strength Cond Res 30(8): 2174–2185, 2016—The purpose of this study was to investigate the hypertrophic, strength, and neuromuscular adaptations to 2 and 4 weeks of resistance training at 80 vs. 30% 1 repetition maximum (1RM) in untrained men. Fifteen untrained men (mean ± SD; age = 21.7 ± 2.4 years; weight = 84.7 ± 23.5 kg) were randomly assigned to either a high-load (n = 7) or low-load (n = 8) resistance training group and completed forearm flexion resistance training to failure 3 times per week for 4 weeks. Forearm flexor muscle thickness (MT) and echo intensity, maximal voluntary isometric (MVIC) and 1RM strength, and the electromyographic, mechanomyographic (MMG), and percent voluntary activation (%VA) responses at 10–100% of MVIC were determined at baseline, 2, and 4 weeks of training. The MT increased from baseline (2.9 ± 0.1 cm) to week 2 (3.0 ± 0.1 cm) and to week 4 (3.1 ± 0.1 cm) for the 80 and 30% 1RM groups. MVIC increased from week 2 (121.5 ± 19.1 Nm) to week 4 (138.6 ± 22.1 Nm) and 1RM increased from baseline (16.7 ± 1.6 kg) to weeks 2 and 4 (19.2 ± 1.9 and 20.5 ± 1.8 kg) in the 80% 1RM group only. The MMG amplitude at 80 and 90% MVIC decreased from baseline to week 4, and %VA increased at 20 and 30% MVIC for both groups. Resistance training to failure at 80 vs. 30% 1RM elicited similar muscle hypertrophy, but only 80% 1RM increased muscle strength. However, these disparate strength adaptations were difficult to explain with neuromuscular adaptations because they were subtle and similar for the 80 and 30% 1RM groups.

The Relationships Among Critical Power Determined From a 3-Min All-Out Test, Respiratory Compensation Point, Gas Exchange Threshold, and Ventilatory Threshold

Purpose: Critical power (CP) from the 3-min test was compared to the power outputs associated with thresholds determined from gas exchange parameters that have been used to demarcate the exercise-intensity domains including the respiratory compensation point (RCP), gas exchange threshold (GET), and ventilatory threshold (VT). Method: Twenty-eight participants performed an incremental-cycle ergometer test to exhaustion. The VT was determined from the relationship between the ventilatory equivalent for oxygen uptake (V˙E/V˙O2) versus V˙O2 and the GET was determined using the V-slope method (V˙CO2 vs. V˙O2). The RCP was identified from the V˙E-versus-V˙CO2 relationship. CP was the average power output during the last 30 s of the 3-min all-out test. Linear regression was used to determine the power outputs associated with the RCP, GET, and VT, as well as the V˙O2 associated with CP. Mean differences among the associated power outputs, percent V˙O2 peak, and percent peak power output for the GET, VT, RCP, and CP were analyzed using separate one-way repeated-measures analyses of variance. Results: There were no significant differences between CP (187 ± 47 W) and the power output associated with RCP (190 ± 49 W) or between the power outputs associated with GET (139 ± 37 W) and VT (145 ± 37 W). The power outputs associated with GET and VT, however, were significantly less than were those at CP and associated with RCP. Conclusions: These findings suggest CP and RCP demarcate the heavy from severe exercise-intensity domain and result from a different mechanism of fatigue than that of GET and VT, possibly hyperkalemia.

Electromyographic and mechanomyographic responses across repeated maximal isometric and concentric muscle actions of the leg extensors

The purpose of the present study was to examine the patterns of responses for torque, electromyographic (EMG) amplitude, EMG mean power frequency (MPF), mechanomyographic (MMG) amplitude, and MMG MPF across 30 repeated maximal isometric (ISO) and concentric (CON) muscle actions of the leg extensors. Twelve female subjects (21.1±1.4yrs; 63.3±7.4kg) performed ISO and CON fatigue protocols with EMG and MMG signals recorded from the vastus lateralis. The relationships for torque, EMG amplitude, EMG MPF, MMG amplitude, and MMG MPF versus repetition number were examined using polynomial regression. The results indicated there were decreases (p<0.05) across the ISO muscle actions for torque (r(2)=0.95), EMG amplitude (R(2)=0.44), EMG MPF (r(2)=0.62), and MMG MPF (r(2)=0.48), but no change in MMG amplitude (r(2)=0.07). In addition, there were decreases across the CON muscle actions for torque (R(2)=0.97), EMG amplitude (R(2)=0.46), EMG MPF (R(2)=0.86), MMG amplitude (R(2)=0.44), and MMG MPF (R(2)=0.80). Thus, the current findings suggested that the mechanisms of fatigue and motor control strategies used to modulate torque production were similar between maximal ISO and CON muscle actions.

Effects of 6 Weeks of Aerobic Exercise Combined With Conjugated Linoleic Acid on the Physical Working Capacity at Fatigue Threshold

Abstract Jenkins, NDM, Buckner, SL, Baker, RB, Bergstrom, HC, Cochrane, KC, Weir, JP, Housh, TJ, and Cramer, JT. Effects of 6 weeks of aerobic exercise combined with conjugated linoleic acid on the physical working capacity at fatigue threshold. J Strength Cond Res 28(8): 2127–2135, 2014—The purpose of this study was to examine the effects of conjugated linoleic acid (CLA) supplementation in conjunction with 6 weeks of aerobic exercise training on the physical working capacity at the fatigue threshold (PWCFT), timed sit-ups, and the standing long jump. Thirty-three untrained to moderately trained men (mean ± SD; age = 21.6 ± 2.8 years) participated in this double-blind, placebo-controlled study and were randomly assigned to either a CLA (Clarinol A-80; n = 17) or placebo (PLA; sunflower oil; n = 16) group. Before and after 6 weeks of aerobic training (50% V[Combining Dot Above]O2peak for 30 minutes, twice per week) and supplementation (8 ml CLA or PLA per day), each subject completed an incremental cycle ergometer test to exhaustion to determine the PWCFT, maximal number of sit-ups in 1 minute, and the standing long jump. There were no differences (all p ≥ 0.23) between the CLA and PLA groups for the analysis of covariance–adjusted posttest mean values for PWCFT, sit-ups, or standing long jump. The PWCFT increased from pre- to posttraining in the CLA (p = 0.003) and PLA (p = 0.003) groups. There were no differences (p > 0.05) from pre- to posttraining for sit-ups and standing long jump in either the CLA or PLA groups. There was no effect of CLA on the training-induced increases in PWCFT, nor were there any effects of CLA or aerobic training on the maximum number of sit-ups or standing long jump. Thus, CLA had no ergogenic benefits on this model of aerobic training–induced improvements in neuromuscular fatigue, or on field tests of muscle endurance and power.

The effects of skinfold thicknesses and innervation zone on the mechanomyographic signal during cycle ergometry

The purpose of this study was to examine the effects of skinfold (SF) thicknesses at four locations on the vastus lateralis (VL) muscle and the placement of accelerometers relative to the innervation zone (IZ) on the mechanomyographic (MMG) amplitude and mean power frequency (MPF) responses during incremental cycle ergometry. Twenty adults (age±SD=23.8±3.0 years) participated in the investigation. The MMG signals were detected during incremental cycle ergometry using four accelerometers placed on the right VL. Prior to the cycle ergometer test, SF thicknesses were measured. Simple linear regression analyses and one-way repeated measures analyses of variance (ANOVAs) were performed. The present study found that only 10% of the regression analyses and mean comparisons were significant (p<0.05). Furthermore, the accelerometer placed at the most proximal site (Prox 2) had significantly greater MMG amplitude and MMG MPF than accelerometers placed at more distal sites (Prox 1, Over IZ, and Dist). There were no significant differences, however, in SF thickness between accelerometer placement sites. In addition, the IZ had no effect on MMG amplitude and little effect on MMG MPF values. The results of the present study indicated that the SF thickness values and IZ did not affect the MMG signal.

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.

Mechanomyographic and Electromyographic Responses During Fatiguing Eccentric Muscle Actions of the Leg Extensors

The purpose of the current study was to examine the patterns of responses for torque, mechanomyographic (MMG) amplitude, MMG frequency, electromyographic (EMG) amplitude, and EMG frequency across 30 repeated maximal eccentric muscle actions of the leg extensors. Eleven moderately trained females performed an eccentric fatigue protocol at 30°/s with MMG and EMG signals recorded from the vastus lateralis. The results indicated there were significant (P<.05) decreases in MMG frequency (linear, r2=.395), EMG frequency (linear, r2=.177), and torque (linear, r2=.570; % decline=9.8±13.3%); increases in MMG amplitude (linear, r2=.783); and no change in EMG amplitude (r2=.003). These findings suggested that the neural strategies used to modulate torque during fatiguing eccentric muscle actions involved de-recruitment of motor units, reduced firing rates, and synchronization. In addition, the decreases in eccentric torque were more closely associated with changes in MMG frequency than EMG frequency. Thus, these findings indicated that MMG frequency, compared with EMG frequency, more accurately tracks fatigue during repeated maximal eccentric muscle actions.

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.

The influence of the muscle fiber pennation angle and innervation zone on the identification of neuromuscular fatigue during cycle ergometry

The purpose of the present investigation was to compare the electromyographic (EMG) responses and the estimated physical working capacity at the fatigue threshold (PWC(FT)) values recorded from electrode arrangements placed: (1) parallel to the muscle fiber pennation angle (MFPA), (2) parallel to the long axis of the femur, and (3) over the innervation zone (IZ) during incremental cycle ergometry. Thirteen college-aged males and females (mean age ± SD=22.4 ± 3.4 years) performed an incremental test to exhaustion on a cycle ergometer. A linear electrode array was utilized to determine the MFPA and location of the IZ of the vastus lateralis (VL). For determination of the PWC(FT) values, EMG signals were recorded from three bipolar electrode arrangements at different locations over the VL. The results of a one-way repeated measures ANOVA indicated there were no significant (p<0.05) mean differences in PWC(FT) values among the electrode arrangements (parallel to the MFPA=190 ± 36 W; parallel to the long axis of the femur=194 ± 40 W; and over the IZ=199 ± 51 W) or the EMG amplitude and MPF values at the common power outputs. There were also significant correlations (r=0.75-0.91) among the three electrode arrangements for PWC(FT) values. These findings suggested that the PWC(FT), like absolute EMG amplitude and MPF, is robust to the influence of electrode placement over the IZ as well as the orientation with respect to the MFPA during cycle ergometry.