Electromyographic and Mechanomyographic Responses at Critical Power

2000 ◽  
Vol 25 (4) ◽  
pp. 262-270 ◽  
Author(s):  
Anthony J. Bull ◽  
Terry J. Housh ◽  
Glen O. Johnson ◽  
Sharon R. Perry
Keyword(s):  
Peak Power ◽  
Critical Power ◽  
Slow Component ◽  
Vastus Lateralis ◽  
Muscular Activity ◽  
Cycle Ergometry ◽  
Slope Coefficient ◽  
The Mean ◽  
Power Outputs ◽  
Amplitude Versus

The purpose of the present study was to determine the electromyographic (EMG) and mechanomyographic (MMG) responses to cycle ergometry at critical power (CP). Seven moderately active males (25 ± 3 years) completed a 60-min trial at their CP estimated from a nonlinear, 3 parameter regression model. EMG and MMG amplitudes were recorded from the vastus lateralis during 60-min continuous rides at CP. The mean CP was 175 ± 25 W, which represented 56 ± 5% of the subjects' peak power outputs. The results indicated that the slope coefficient for the EMG amplitude versus time relationship was not significantly different from zero; however, MMG amplitude decreased significantly over the 60 min. This dissociation between the electrical (EMG) and mechanical (MMG) aspects of muscular activity during cycle ergometry may be due to neuromuscular changes associated with "muscle wisdom" or changes in muscular compliance. Key words: cycle ergometry, fatigue, muscle wisdom, [Formula: see text] slow component

scholarly journals Vitamin and mineral supplementation effect on muscular activity and cycling efficiency in master athletes

2010 ◽  
Vol 35 (3) ◽  
pp. 251-260 ◽  
Author(s):  
Julien Louis ◽  
Christophe Hausswirth ◽  
François Bieuzen ◽  
Jeanick Brisswalter
Keyword(s):  
Slow Component ◽  
Vastus Lateralis ◽  
Muscular Activity ◽  
Knee Extensors ◽  
Emg Activity ◽  
Master Athletes ◽  
Double Blind ◽  
Mineral Complex ◽  
Cycling Efficiency ◽  
Fatiguing Exercise

The influence of vitamin and mineral complex supplementation on muscular activity and cycling efficiency was examined in elderly endurance-trained master athletes during a heavy cycling trial. Master athletes were randomly assigned in a double-blind process to 1 of 2 treatment groups: antioxidant supplementation (n = 8: As group) or placebo (n = 8: Pl group) for 21 days. After that time, each subject had to perform a 10-min session of cycling on a cycloergometer at a heavy constant intensity. Twenty-four to 48 h after this session, subjects performed an isometric maximal voluntary contraction before and immediately after a fatiguing strength training (leg press exercise) and the same 10-min cycling test after fatigue. Isometric maximal voluntary force (MVF) of knee extensors was assessed before and after fatigue. Electromyographic (EMG) activity of the vastus medialis, the vastus lateralis (VL), and the biceps femoris was recorded with surface EMG. The knee-extensors MVF after the fatiguing exercise was reduced in similar proportions for both groups (As, –10.9%; Pl, –11.3%, p < 0.05). This MVF loss was associated with a significant reduction in EMG frequency parameters for both groups, with a lower decrease for the As group. Muscular activity and cycling efficiency during the cycling bouts were affected by the treatment. Cycling efficiency decreased significantly and the oxygen uptake slow component was higher after the fatiguing exercise for both groups. Furthermore, a decrease in cycling efficiency was associated with an increase in VL activity. However, these changes were significantly lower for the As group. The results of the present study indicate an overall positive effect of vitamin and mineral complex supplementation on cycling efficiency after fatigue, in the endurance-trained elderly.

Influence of crank rate on the slow component of pulmonary O2 uptake during heavy arm-crank exercise

2006 ◽  
Vol 31 (3) ◽  
pp. 292-301 ◽  
Author(s):  
Paul M Smith ◽  
Eilidh McCrindle ◽  
Mike Doherty ◽  
Michael J Price ◽  
Andrew M Jones
Keyword(s):  
Oxygen Uptake ◽  
Peak Power ◽  
Slow Component ◽  
Work Rate ◽  
Rating Of Perceived Exertion ◽  
Muscle Fibres ◽  
External Work ◽  
Tension Development ◽  
Significant Difference ◽  
The Mean

The principal aim of this study was to examine the influence of variations in crank rate on the slow component of the pulmonary oxygen uptake ([Formula: see text]O2) response to heavy-intensity arm-crank ergometry (ACE). We hypothesized that, for the same external work rate, a higher crank rate would elicit a greater amplitude of the [Formula: see text]O2 "slow component". Eleven healthy males (mean (± SD) age, 25 (±6) y; body mass, 89.1 (±10.7) kg; ACE [Formula: see text]O2 peak, 3.36 (±0.47) L·min-1) volunteered to participate. The subjects initially completed an incremental exercise test for the determination of [Formula: see text]O2 peak and peak power on an electrically braked arm ergometer. Subsequently, they completed "step" transitions from an unloaded baseline to a work rate requiring 70% of peak power: 2 at a crank rate of 50 r·min-1 (LO) and 2 at a crank rate of 90 r·min-1 (HI). Pulmonary gas exchange was measured on a breath-by-breath basis and [Formula: see text]O2 kinetics were evaluated from the mean response to each condition using non-linear regression techniques. In contradiction to our hypothesis, the [Formula: see text]O2 slow component was significantly greater at 50 r·min-1 than at 90 r·min-1 (LO: 0.60 ± 0.30 vs. HI: 0.47 ± 0.21 L·min-1; p < 0.05). The mean value for the localized rating of perceived exertion was also higher at 50 r·min-1 than at 90 r·min-1 (LO: 16.7 ± 1.4 vs. HI: 15.2 ± 1.3; p < 0.05), but there was no significant difference in end-exercise blood lactate concentration. It is possible that differences in muscle tension development and blood flow resulted in a greater contribution of "low-efficiency" type II muscle fibres to force production at the lower crank rate in ACE, and that this was linked to the greater [Formula: see text]O2 slow component. However, other factors such as greater isometric contraction of the muscles of the trunk and legs at the lower crank rate might also be implicated.Key words: O2 kinetics, [Formula: see text]O2 slow component, fibre recruitment, oxygen uptake.

scholarly journals Leg Muscle Activity and Perception of Effort before and after Four Short Sessions of Submaximal Eccentric Cycling

2020 ◽  
Vol 17 (21) ◽  
pp. 7702
Author(s):  
Pierre Clos ◽  
Romuald Lepers
Keyword(s):  
Muscle Activity ◽  
Peak Power ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Peak Power Output ◽  
Leg Muscles ◽  
Perception Of Effort ◽  
Before And After ◽  
Power Outputs

Background: This study tested muscle activity (EMG) and perception of effort in eccentric (ECC) and concentric (CON) cycling before and after four sessions of both. Methods: Twelve volunteers naïve to ECC cycling attended the laboratory six times. On day 1, they performed a CON cycling peak power output (PPO) test. They then carried-out four sessions comprising two sets of 1 to 1.5-min cycling bouts at 5 intensities (30, 45, 60, 75, and 90% PPO) in ECC and CON cycling. On day 2 and day 6 (two weeks apart), EMG root mean square of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and soleus (SOL) muscles, was averaged from 15 to 30 s within each 1-min bout and perception of effort was asked after 45 s. Results: Before the four cycling sessions, while VL EMG was lower in ECC than CON cycling, most variables were not different. Afterwards, ECC cycling exhibited lower RF EMG at 75 and 90% PPO (all p < 0.02), lower VL and BF EMG at all exercise intensities (all p < 0.02), and inferior SOL EMG (all p < 0.04) except at 45% PPO (p = 0.07). Perception of effort was lower in ECC cycling at all exercise intensities (all p < 0.03) but 60% PPO (p = 0.11). Conclusions: After four short sessions of ECC cycling, the activity of four leg muscles and perception of effort became lower in ECC than in CON cycling at most of five power outputs, while they were similar before.

Sprinting for the Win: Distribution of Power Output in Women’s Professional Cycling

2018 ◽  
Vol 13 (9) ◽  
pp. 1237-1242 ◽  
Author(s):  
Jeremiah J. Peiffer ◽  
Chris R. Abbiss ◽  
Eric C. Haakonssen ◽  
Paolo Menaspà
Keyword(s):  
Power Output ◽  
Peak Power ◽  
Peak Power Output ◽  
Maximal Power Output ◽  
Variable Nature ◽  
The Mean ◽  
Road Cyclists ◽  
Distribution Of Power ◽  
Power Outputs ◽  
Professional Cycling

Purpose:To examine the power-output distribution and sprint characteristics of professional female road cyclists.Methods:A total of 31 race files, representing top 5 finishes, were collected from 7 professional female cyclists. Files were analyzed for sprint characteristics, including mean and peak power output, velocity, and duration. The final 20 min before the sprint was analyzed to determine the mean maximal power output (MMP) consistent with durations of 5, 15, 30, 60, 240, and 600 s. Throughout the race, the number of efforts for each duration exceeding 80% of its corresponding final 20-min MMP (MMP80) was determined. The number of 15-s efforts exceeding 80% of the mean final sprint power output (MSP80) was determined.Results:Sprint finishes lasted 21.8 (6.7) s with mean and peak power outputs of 679 (101) and 886 (91) W, respectively. Throughout the race, additional 5-, 15-, and 30-s efforts above MMP80were completed in the 5th compared with the 1st–4th quintiles of the race. The 60-s efforts were greater during the 5th quintile compared with the 1st, 2nd, and 4th quintiles, and during the 3rd compared with the 4th quintile. More 240-s efforts were recorded during the 5th compared with the 1st and 4th quintiles. About 82% of the 15-s efforts above MSP80were completed in the 2nd, 3rd, and 5th quintiles of the race.Conclusions:These data demonstrate the variable nature of women’s professional cycling and the physical demands necessary for success, thus providing information that could enhance in-race decision making and the development of race-specific training programs.

scholarly journals Effective Activation of BKCa Channels by QO-40 (5-(Chloromethyl)-3-(Naphthalen-1-yl)-2-(Trifluoromethyl)Pyrazolo [1,5-a]pyrimidin-7(4H)-one), Known to Be an Opener of KCNQ2/Q3 Channels

2021 ◽  
Vol 14 (5) ◽  
pp. 388
Author(s):  
Wei-Ting Chang ◽  
Sheng-Nan Wu
Keyword(s):  
Single Channel ◽  
Slow Component ◽  
Ionic Channel ◽  
Gh3 Cells ◽  
Bkca Channel ◽  
Bkca Channels ◽  
Gating Charge ◽  
Ramp Voltage ◽  
K Current ◽  
The Mean

QO-40 (5-(chloromethyl)-3-(naphthalene-1-yl)-2-(trifluoromethyl) pyrazolo[1,5-a]pyrimidin-7(4H)-one) is a novel and selective activator of KCNQ2/KCNQ3 K+ channels. However, it remains largely unknown whether this compound can modify any other type of plasmalemmal ionic channel. The effects of QO-40 on ion channels in pituitary GH3 lactotrophs were investigated in this study. QO-40 stimulated Ca2+-activated K+ current (IK(Ca)) with an EC50 value of 2.3 μM in these cells. QO-40-stimulated IK(Ca) was attenuated by the further addition of GAL-021 or paxilline but not by linopirdine or TRAM-34. In inside-out mode, this compound added to the intracellular leaflet of the detached patches stimulated large-conductance Ca2+-activated K+ (BKCa) channels with no change in single-channel conductance; however, there was a decrease in the slow component of the mean closed time of BKCa channels. The KD value required for the QO-40-mediated decrease in the slow component at the mean closure time was 1.96 μM. This compound shifted the steady-state activation curve of BKCa channels to a less positive voltage and decreased the gating charge of the channel. The application of QO-40 also increased the hysteretic strength of BKCa channels elicited by a long-lasting isosceles-triangular ramp voltage. In HEK293T cells expressing α-hSlo, QO-40 stimulated BKCa channel activity. Overall, these findings demonstrate that QO-40 can interact directly with the BKCa channel to increase the amplitude of IK(Ca) in GH3 cells.

Use of A GAS Jet Technique to Prepare Microcrystalline Silicon Based Solar Cells at High I-Layer Deposition Rates

1999 ◽  
Vol 557 ◽  
Author(s):  
S.J. Jones ◽  
R. Crucet ◽  
X. Deng ◽  
J. Doehler ◽  
R. Kopf ◽  
...  
Keyword(s):  
Solar Cells ◽  
Peak Power ◽  
Light Exposure ◽  
Red Light ◽  
Gas Jet ◽  
Scale Production ◽  
Microcrystalline Silicon ◽  
Deposition Rates ◽  
Layer Deposition ◽  
Power Outputs

AbstractUsing a Gas Jet thin film deposition technique, microcrystalline silicon (μc-Si) materials were prepared at rates as high as 15-20 Å/s. The technique involves the use of a gas jet flow that is subjected to a high intensity microwave source. The quality of the material has been optimized through the variation of a number of deposition conditions including the substrate temperature, the gas flows, and the applied microwave power. The best films were made using deposition rates near 16 Å/s. These materials have been used as i-layers for red light absorbing, nip single-junction solar cells. Using a 610nm cutoff filter which only allows red light to strike the device, pre-light soaked currents as high as 10 mA/cm2 and 2.2-2.3% red-light pre-light soaked peak power outputs have been obtained for cells with i-layer thicknesses near 1 micron. This compares with currents of 10-11 mA/cm2 and 4% initial red-light peak power outputs obtained for high efficiency amorphous silicon germanium alloy (a-SiGe:H) devices. The AM1.5 white light efficiencies for these microcrystalline cells are 5.9-6.0%. While the efficiencies for the a-SiGe:H cells degrade by 15-20% after long term light exposure, the efficiencies for the microcrystalline cells before and after prolonged light exposure are similar, within measurement error. Considering these results, the Gas Jet deposition method is a promising technique for the deposition of μc-Si solar cells due to the ability to achieve reasonable stable efficiencies for cells at i-layer deposition rates (16 Å/s) which make large-scale production economically feasible.

scholarly journals Energy cost and muscular activity required for propulsion during walking

2003 ◽  
Vol 94 (5) ◽  
pp. 1766-1772 ◽  
Author(s):  
Jinger S. Gottschall ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Muscular Activity ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Horizontal Force ◽  
Normal Walking ◽  
The Mean ◽  
The Cost ◽  
Muscle Actions

We reasoned that with an optimal aiding horizontal force, the reduction in metabolic rate would reflect the cost of generating propulsive forces during normal walking. Furthermore, the reductions in ankle extensor electromyographic (EMG) activity would indicate the propulsive muscle actions. We applied horizontal forces at the waist, ranging from 15% body weight aiding to 15% body weight impeding, while subjects walked at 1.25 m/s. With an aiding horizontal force of 10% body weight, 1) the net metabolic cost of walking decreased to a minimum of 53% of normal walking, 2) the mean EMG of the medial gastrocnemius (MG) during the propulsive phase decreased to 59% of the normal walking magnitude, and yet 3) the mean EMG of the soleus (Sol) did not decrease significantly. Our data indicate that generating horizontal propulsive forces constitutes nearly half of the metabolic cost of normal walking. Additionally, it appears that the MG plays an important role in forward propulsion, whereas the Sol does not.

Electrical activity and relative length changes of dog limb muscles as a function of speed and gait

1981 ◽  
Vol 94 (1) ◽  
pp. 15-42 ◽  
Author(s):  
G. E. Goslow ◽  
H. J. Seeherman ◽  
C. R. Taylor ◽  
M. N. McCutchin ◽  
N. C. Heglund
Keyword(s):  
Electrical Activity ◽  
Stance Phase ◽  
Biceps Brachii ◽  
Vastus Lateralis ◽  
Activity Patterns ◽  
Relative Length ◽  
Muscular Activity ◽  
Triceps Brachii ◽  
Limb Muscles ◽  
Length Changes

Electrical activity and length changes of 11 muscles of the fore- and hind- limbs of dogs walking, running, and galloping on a treadmill, were measured as a function of forward speed and gait. Our purpose was to find out whether the activity patterns of the major limb muscles were consistent with the two mechanisms proposed for storage and recovery of energy within a stride: a ‘pendulum-like’ mechanism during a walk, and a ‘spring-like’ mechanism during a run. In the stance phase of the walking dog, we found that the supraspinatus, long head of the triceps brachii, biceps brachii, vastus lateralis, and gastrocnemius underwent only minor length changes during a relatively long portion of their activity, Thus, a major part of their activity during the walk seems consistent with a role in stabilization of the joints as the dog ‘pole-vaulted’ over its limbs (and thereby conserved energy). In the stance phase of trotting and/or galloping dogs, we found that the supraspinatus, lateral head of the triceps, vastus lateralis, and gastrocnemius were active while being stretched prior to shortening (as would be required for elastic storage of energy), and that this type of activity increased with increasing speed. We also found muscular activity in the select limb flexors that was consistent with storage of kinetic energy at the end of the swing phase and recovery during the propulsive stroke. This activity pattern was apparent in the latissimus dorsi during a walk and trot, and in the biceps femoris during a trot and gallop. We conclude that, during locomotion, a significant fraction of the electrical activity of a number of limbs muscles occurs while they undergo little or no length change or are being stretched prior to shortening and that these types of activities occur in a manner that would enable the operation of pendulum-like and spring-like mechanisms for conserving energy within a stride. Therefore these forms of muscular activity, in addition to the more familiar activity associated with muscle shortening, should be considered to be important during locomotion.

Performance comparison between dual cantilevered and touch based hybridized triboelectric harvesters

2021 ◽  
Vol 15 (1) ◽  
pp. 7754-7761
Author(s):  
Satish Rao Ganapathy ◽  
H. Salleh
Keyword(s):  
Low Power ◽  
Surface Area ◽  
Peak Power ◽  
Energy Harvester ◽  
Dissimilar Materials ◽  
Performance Comparison ◽  
Effective Length ◽  
Surface Charges ◽  
Generate Surface ◽  
Power Outputs

The demand for energy harvesting technologies has been increasing over the years attributed to its significance to low power applications. One of the key problems associated with the vibration-based harvester is the fact that these harvesters generate low usable power while maximum peak power can only be attained when the device frequency matches the source frequency. In this study, triboelectric mechanism was investigated in combination with the piezoelectric mechanism in order to enhance the performance of the harvester. Triboelectric mechanism functions in a way that two dissimilar materials were placed in contact and then separated in order to generate surface charges and electric potential between them. Main design factors such as materials, surface area, structure, effective length, and etc. play a significant part in the enhancement of the performance. This study proposed two distinct designs of dual cantilevered structure and touch-based triboelectric energy harvester and evaluated the efficiency of the output between both structures. In addition, the effect of extension and surface area of triboelectric materials was investigated while the influence of these factors on the performance of the harvester was evaluated. The highest value of peak power obtained for dual cantilevered hybrid harvester was 650 µW across a load of 160 kΩ and frequency of 26 Hz. On the other hand, touch-based energy harvester produced an output peak power of 1220 µW across a load of 400 kΩ at 25 Hz. Achieving these power outputs may be able to power up electronics such as smartwatches, hearing aid and etc. Future studies on reliable low power applications to further advance the green power technology will be investigated.

Carbohydrate Drink Use During 30 Minutes of Variable-Intensity Exercise Has No Effect on Exercise Performance in Premenarchal Girls

2021 ◽  
Vol 33 (2) ◽  
pp. 65-69
Author(s):  
C. Eric Heidorn ◽  
Brandon J. Dykstra ◽  
Cori A. Conner ◽  
Anthony D. Mahon
Keyword(s):  
Peak Power ◽  
Perceived Exertion ◽  
Rating Of Perceived Exertion ◽  
Fatigue Index ◽  
Mean Power ◽  
Variable Intensity ◽  
Performance Effects ◽  
Power Peak ◽  
The Mean ◽  
And Performance

Purpose: This study examined the physiological, perceptual, and performance effects of a 6% carbohydrate (CHO) drink during variable-intensity exercise (VIE) and a postexercise test in premenarchal girls. Methods: A total of 10 girls (10.4 [0.7] y) participated in the study. VO2peak was assessed, and the girls were familiarized with VIE and performance during the first visit. The trial order (CHO and placebo) was randomly assigned for subsequent visits. The drinks were given before VIE bouts and 1-minute performance (9 mL/kg total). Two 15-minute bouts of VIE were completed (10 repeated sequences of 20%, 55%, and 95% power at VO2peak and maximal sprints) before a 1-minute performance sprint. Results: The mean power, peak power, heart rate (HR), %HRpeak, and rating of perceived exertion during VIE did not differ between trials. However, the peak power decreased, and the rating of perceived exertion increased from the first to the second bout. During the 1-minute performance, there were no differences between the trial (CHO vs placebo) for HR (190 [9] vs 189 [9] bpm), %HRpeak (97.0% [3.2%] vs 96.6% [3.0%]), rating of perceived exertion (7.8 [2.3] vs 8.1 [1.9]), peak power (238 [70] vs 235 [60] W), fatigue index (54.7% [10.0%] vs 55.9% [12.8%]), or total work (9.4 [2.6] vs 9.4 [2.1] kJ). Conclusion: CHO supplementation did not alter physiological, perceptual, or performance responses during 30 minutes of VIE or postexercise sprint performance in premenarchal girls.

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