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 (V̇O2peak) and gas exchange threshold. CP was estimated for each subject from the 3-min all-out test. Oxygen consumption (V̇O2), the ventilation versus carbon dioxide production ratio (V̇E/V̇CO2 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 V̇O2 at exhaustion (40.6 ± 7.5 mL·kg−1·min−1) and V̇O2peak (42.9 ± 7.3 mL·kg−1·min−1). Furthermore, there were significant increases in EMG amplitude and the V̇E/V̇CO2 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 V̇O2, 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.

Download Full-text

Relationship Between the Critical Power Test and a 20-min Functional Threshold Power Test in Cycling

Frontiers in Physiology ◽

10.3389/fphys.2020.613151 ◽

2021 ◽

Vol 11 ◽

Author(s):

Bettina Karsten ◽

Luca Petrigna ◽

Andreas Klose ◽

Antonino Bianco ◽

Nathan Townsend ◽

...

Keyword(s):

Critical Power ◽

Pearson Correlation ◽

Time Trial ◽

Peak Oxygen Consumption ◽

Threshold Power ◽

Strong Correlations ◽

Mean Power ◽

Power Test ◽

Paired Samples ◽

The Mean

To investigate the agreement between critical power (CP) and functional threshold power (FTP), 17 trained cyclists and triathletes (mean ± SD: age 31 ± 9 years, body mass 80 ± 10 kg, maximal aerobic power 350 ± 56 W, peak oxygen consumption 51 ± 10 mL⋅min–1⋅kg–1) performed a maximal incremental ramp test, a single-visit CP test and a 20-min time trial (TT) test in randomized order on three different days. CP was determined using a time-trial (TT) protocol of three durations (12, 7, and 3 min) interspersed by 30 min passive rest. FTP was calculated as 95% of 20-min mean power achieved during the TT. Differences between means were examined using magnitude-based inferences and a paired-samples t-test. Effect sizes are reported as Cohen’s d. Agreement between CP and FTP was assessed using the 95% limits of agreement (LoA) method and Pearson correlation coefficient. There was a 91.7% probability that CP (256 ± 50 W) was higher than FTP (249 ± 44 W). Indeed, CP was significantly higher compared to FTP (P = 0.041) which was associated with a trivial effect size (d = 0.04). The mean bias between CP and FTP was 7 ± 13 W and LoA were −19 to 33 W. Even though strong correlations exist between CP and FTP (r = 0.969; P < 0.001), the chance of meaningful differences in terms of performance (1% smallest worthwhile change), were greater than 90%. With relatively large ranges for LoA between variables, these values generally should not be used interchangeably. Caution should consequently be exercised when choosing between FTP and CP for the purposes of performance analysis.

Download Full-text

Inter- and Intra-Individual Differences in EMG and MMG during Maximal, Bilateral, Dynamic Leg Extensions

Sports ◽

10.3390/sports7070175 ◽

2019 ◽

Vol 7 (7) ◽

pp. 175 ◽

Cited By ~ 5

Author(s):

John Paul V. Anders ◽

Cory M. Smith ◽

Joshua L. Keller ◽

Ethan C. Hill ◽

Terry J. Housh ◽

...

Keyword(s):

Individual Differences ◽

Repeated Measures ◽

Polynomial Regression ◽

Vastus Lateralis ◽

Regression Analyses ◽

Mean Power ◽

Mean Power Frequency ◽

Leg Extension ◽

Neuromuscular Responses ◽

Muscle Actions

The purpose of this study was to compare the composite, inter-individual, and intra-individual differences in the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during fatiguing, maximal, bilateral, and isokinetic leg extension muscle actions. Thirteen recreationally active men (age = 21.7 ± 2.6 years; body mass = 79.8 ± 11.5 kg; height = 174.2 ± 12.7 cm) performed maximal, bilateral leg extensions at 180°·s−1 until the torque values dropped to 50% of peak torque for two consecutive repetitions. The EMG and MMG signals from the vastus lateralis (VL) muscles of both limbs were recorded. Four 2(Leg) × 19(time) repeated measures ANOVAs were conducted to examine mean differences for EMG AMP, EMG MPF, MMG AMP, and MMG MPF between limbs, and polynomial regression analyses were performed to identify the patterns of neuromuscular responses. The results indicated no significant differences between limbs for EMG AMP (p = 0.44), EMG MPF (p = 0.33), MMG AMP (p = 0.89), or MMG MPF (p = 0.52). Polynomial regression analyses demonstrated substantial inter-individual variability. Inferences made regarding the patterns of neuromuscular responses to fatiguing and bilateral muscle actions should be considered on a subject-by-subject basis.

Download Full-text

Interlimb Neuromuscular Responses During Fatiguing, Bilateral, Leg Extension Exercise at a Moderate Versus High Load

Motor Control ◽

10.1123/mc.2020-0050 ◽

2021 ◽

Vol 25 (1) ◽

pp. 59-74

Author(s):

Taylor K. Dinyer ◽

Pasquale J. Succi ◽

M. Travis Byrd ◽

Caleb C. Voskuil ◽

Evangeline P. Soucie ◽

...

Keyword(s):

Vastus Lateralis ◽

High Load ◽

Mean Power ◽

Mean Power Frequency ◽

Leg Extension ◽

Neuromuscular Responses ◽

Power Frequency ◽

The Central Nervous System ◽

Common Drive ◽

Repetitions To Failure

This study determined the load- and limb-dependent neuromuscular responses to fatiguing, bilateral, leg extension exercise performed at a moderate (50% one-repetition maximum [1RM]) and high load (80% 1RM). Twelve subjects completed 1RM testing for the bilateral leg extension, followed by repetitions to failure at 50% and 80% 1RM, on separate days. During all visits, the electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) signals were recorded from the vastus lateralis of both limbs. There were no limb-dependent responses for any of the neuromuscular signals and no load-dependent responses for EMG AMP, MMG AMP, or MMG MPF (p = .301–.757), but there were main effects for time that indicated increases in EMG and MMG AMP and decreases in MMG MPF. There was a load-dependent decrease in EMG MPF over time (p = .032) that suggested variability in the mechanism responsible for metabolite accumulation at moderate versus high loads. These findings suggested that common drive from the central nervous system was used to modulate force during bilateral leg extension performed at moderate and high loads.

Download Full-text

Aircraft Passenger Comfort Based on Muscle Activation and Perceived Discomfort During Long Flights

Aerospace Medicine and Human Performance ◽

10.3357/amhp.5201.2020 ◽

2020 ◽

Vol 91 (5) ◽

pp. 416-421

Author(s):

Huining Pei ◽

Suihuai Yu ◽

Man Ding ◽

Zhonghang Bai

Keyword(s):

Muscle Activation ◽

Upper Body ◽

Mean Power ◽

Mean Power Frequency ◽

Passenger Comfort ◽

Body Regions ◽

Lower Back ◽

Significant Difference ◽

Power Frequency ◽

Subjective Discomfort

OBJECTIVE: The purpose of this study was to investigate the comfort of aircraft passengers during long flights and to determine the effects of the seatback angle and the seat pitch on passengers’ upper body muscles (neck, shoulder, and lower back) and subjective comfort.METHODS: All subjects sat on an aircraft seat for 2 h with different levels of seatback angle and seat pitch. Subjective discomfort scores and root mean square (RMS) and mean power frequency (MPF) values were used to evaluate muscle fatigue, and all data were calculated for every 15-min interval.RESULTS: Significant increases of MPF for all three muscles were found at 30 min, along with significant increases in the perceived levels of discomfort (PLD) over 2 h. Besides, a 120° seatback angle and a 34˝ seat pitch resulted in lower PLD values for the lower back and hip areas than smaller ones (significant difference).DISCUSSION: It took around 30 min before pronounced discomfort in the upper body regions occurred during flight. The larger parameters of seatback angle and seat pitch may significantly contribute to the easing of subjective discomfort. Moreover, a decrease in MPF coupled with a concomitant increase in RMS does not appear to be a reliable indicator of discomfort rate. The need for further development of discomfort indicators which are more directly related to muscular activation is recognized.Pei H, Yu S, Ding M, Bai Z. Aircraft passenger comfort based on muscle activation and perceived discomfort during long flights. Aerosp Med Hum Perform. 2020; 91(5):416–421.

Download Full-text

The Effect of Balance on the Determination of Peak Oxygen Consumption for Hearing and Nonhearing Female Athletes

Adapted Physical Activity Quarterly ◽

10.1123/apaq.10.3.216 ◽

1993 ◽

Vol 10 (3) ◽

pp. 216-225 ◽

Cited By ~ 2

Author(s):

M. Kathleen Ellis ◽

Lynn A. Darby

Keyword(s):

Oxygen Consumption ◽

Female Athletes ◽

Dynamic Balance ◽

Bicycle Ergometer ◽

Peak Oxygen Consumption ◽

Intercollegiate Athletes ◽

Significant Difference ◽

Two Measures ◽

Exercise Equipment

This study compared balance and peak oxygen consumption (peak VO2) among hearing, congenital nonhearing, and acquired nonhearing female intercollegiate athletes. Twenty-seven subjects completed two measures of peak VO2 and two measures of balance (static and dynamic). Two pieces of exercise equipment requiring different levels of balance were used: the bicycle ergometer (minimal balance) and the bench-step (maximal balance). Significant differences were found for dynamic balance and for peak VO2 for all subject groups. The significant difference remained among the groups for peak VO2 using the bicycle ergometer when dynamic balance was used as a covariate. There was no significant difference for peak VO2 dependent on type of test when dynamic balance was controlled. The results indicated that dynamic balance affected peak VO2 performance on the bench-step, but not on the bicycle ergometer. These findings suggest that if dynamic balance is required for an assessment of peak VO2, balance should be tested in nonhearing populations.

Download Full-text

Muscular endurance and surface electromyogram in isometric and dynamic exercise

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.1.1 ◽

1981 ◽

Vol 51 (1) ◽

pp. 1-7 ◽

Cited By ~ 175

Author(s):

M. Hagberg

Keyword(s):

Maximum Voluntary Contraction ◽

Isometric Exercise ◽

Voluntary Contraction ◽

Dynamic Exercise ◽

Mean Power ◽

Mean Power Frequency ◽

Endurance Time ◽

Significant Difference ◽

Power Frequency ◽

The Mean

In nine male volunteers, the endurance time for sustained isometric exercise (right-angle elbow flexion) and dynamic exercise (continuous concentric and eccentric elbow flexions) was measured at different contraction levels. Intermittent isometric exercises were also performed by four of the subjects in whom surface electromyographic elbow flexor recordings were obtained during the three types of exercise. A rapid decrease of the endurance time was seen at contraction levels above 15–20% of the maximum voluntary contraction for both the sustained isometric and dynamic exercise. There were no significant difference between the regression of the endurance time vs. the contraction level for the sustained isometric exercise and that of the dynamic exercise. However, the endurance time was enhanced in the intermittent isometric exercise compared with the sustained isometric exercise. The development of muscle fatigue was well correlated to change of the myoelectric rootmean-square amplitude and the mean power frequency. Differences in exercise did not significantly affect the relation between the time constant of the mean power frequency decrease and the endurance time.

Download Full-text

Effects of muscle kinematics on surface EMG amplitude and frequency during fatiguing dynamic contractions

Journal of Applied Physiology ◽

10.1152/jappl.1997.82.1.144 ◽

1997 ◽

Vol 82 (1) ◽

pp. 144-151 ◽

Cited By ~ 84

Author(s):

J. R. Potvin

Keyword(s):

Biceps Brachii ◽

Elbow Flexion ◽

Surface Emg ◽

Mean Power ◽

Mean Power Frequency ◽

Emg Amplitude ◽

Flexion Extension ◽

Dynamic Contractions ◽

Power Frequency ◽

Voluntary Contractions

Potvin, J. R. Effects of muscle kinematics on surface EMG amplitude and frequency during fatiguing dynamic contractions. J. Appl. Physiol. 82(1): 144–151, 1997.—Fifteen male subjects performed a repetitive elbow flexion/extension task with a 7-kg mass until exhaustion. Average joint angle, angular velocity, and biceps brachii surface electromyographic (EMG) amplitude (aEMG) and mean power frequency (MPF) were calculated with each consecutive 250-ms segment of data during the entire trial. Data were separated into concentric or eccentric phases and into seven 20°-ranges from 0 to 140° of elbow flexion. A regression analysis was used to estimate the rested and fatigued aEMG and MPF values. aEMG values were expressed as a percentage of amplitudes from maximum voluntary contractions (MVC). Under rested dynamic conditions, the average concentric aEMG amplitude was 10% MVC higher than average eccentric values. Rested MPF values were similar for concentric and eccentric phases, although values increased ∼20 Hz from the most extended to flexed joint angles. Fatigue resulted in an average increase in concentric and eccentric aEMG of 35 and 10% MVC, respectively. The largest concentric aEMG increases (up to 58% MVC) were observed at higher joint velocities, whereas eccentric increases appeared to be related to decreases in velocity. Fatigue had a similar effect on MPF during both concentric and eccentric phases. Larger MPF decreases were observed at shorter muscle lengths such that values within each angle range were very similar by the end of the trial. It was hypothesized that this finding may reflect a biological minimum in conduction velocity before propagation failure occurs.

Download Full-text

Effects of Different Sling Settings on Electromyographic Activities of Selected Trunk Muscles: A Preliminary Research

BioMed Research International ◽

10.1155/2020/2945952 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Xin Li ◽

Howe Liu ◽

Ke-yu Lin ◽

Ping Miao ◽

Bao-feng Zhang ◽

...

Keyword(s):

Erector Spinae ◽

Transversus Abdominis ◽

Trunk Muscles ◽

Emg Activity ◽

Lumbar Region ◽

Mean Power ◽

Mean Power Frequency ◽

Effective Measure ◽

Significant Difference ◽

Dominant Side

Introduction. The supine and prone sling exercise may facilitate activation of the local trunk muscles. Does the side-lying sling exercise activate trunk muscles more easily than the supine and prone training with sling settings? Clinical work has shown that the side-lying sling exercise could reduce pain in patients with unilateral low back pain (LBP), but the mechanism behind it is unclear. The fundamental purpose of this preliminary study was to examine the electromyography (EMG) characteristics of trunk muscles during different sling lumbar settings on sixteen healthy adults. Methods. Amplitude and mean power frequency (MPF) of EMG signals were recorded from the transversus abdominis (TA), rectus abdominis (RA), multifidus (MF), erector spinae (ES), gluteus maximus (Gmax), and gluteus medius (Gmed) muscles while the subjects performed the supine lumbar setting (SLS), prone lumbar setting (PLS), left side-lying lumbar setting (LSLS), and right side-lying lumbar setting (RSLS). Results. During SLS and PLS, TA and MF showed significantly higher activity than RA and ES on the same side, respectively. The EMG activities of ES, TA, MF, Gmax, and Gmed had significant differences between the different sides during LSLS and RSLS, and the dominant-side muscles showed higher activity than the other side. There was no significant difference in core trunk muscles between different sling lumbar settings—only that the SLS of the MF/ES ratio was significantly higher than LSLS and RSLS. Conclusions. Sling exercises can be an effective measure to enhance MF and TA EMG activity, and the side-lying position can increase dominant-side Gmax and Gmed activity. Side-lying sling training does not activate more core muscles than the supine and prone training. Supine and prone exercise should be preferred over SLT to stabilize the lumbar region because of its high local/global muscle ratio.

Download Full-text

Mechanomyography-based assessment during repetitive sit-to-stand and stand-to-sit in two incomplete spinal cord-injured individuals

Biomedical Engineering / Biomedizinische Technik ◽

10.1515/bmt-2018-0200 ◽

2020 ◽

Vol 65 (2) ◽

pp. 175-181

Author(s):

Musfirah Abd Aziz ◽

Nur Azah Hamzaid ◽

Nazirah Hasnan ◽

Muhammad Afiq Dzulkifli

Keyword(s):

Spinal Cord ◽

Root Mean Square ◽

Functional Independence ◽

Mean Square ◽

Monitoring Tool ◽

Mean Power ◽

Mean Power Frequency ◽

Sit To Stand ◽

Significant Difference ◽

Cord Injury

AbstractStanding up and sitting down movements are important prerequisites to achieve functional independence in everyday life of spinal cord injury (SCI) patients. Thus, mechanomyography (MMG) was proposed as a safe monitoring tool to evaluate muscle function performance of these activities. Two incomplete SCI participants performed repetitive sit-to-stand (SitTS) and stand-to-sit (StandTS) until fatigued challenge. Three sets of these activities were completed with MMG sensors attached over the quadriceps muscles of both legs. A 5-min rest was allocated between each set, totalling 399 trials of SitTS and StandTS activities. There was a significant difference between MMG’s mean root mean square maximum (RMSmax) in SitTS and StandTS activities (p = 0.014). The mean values of RMSmax and root mean square average (RMSave) on the right leg were detected to be significantly higher compared to those of the left leg during these activities (p < 0.05). In the frequency domain, MMG’s mean power frequency (MPF) proved to be significantly higher at the beginning compared to the end of the three sets of both activities (p = 0.000). These muscle performances during both activities can be verified based on the analysis of MMG behaviour in time and frequency domains. Furthermore, this study indicated that MMG can be used as a monitoring tool to identify muscle fatigue throughout a prolonged event.

Download Full-text