THE EFFECT OF LEG PREFERENCE ON MECHANICAL EFFICIENCY DURING SINGLE-LEG EXTENSION EXERCISE

2021 ◽  
Author(s):  
Massimo Venturelli ◽  
Cantor Tarperi ◽  
Chiara Milanese ◽  
Luca Festa ◽  
Luana Toniolo ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Near Infrared ◽  
Isometric Force ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Critical Role ◽  
Inverse Correlation ◽  
Mechanical Efficiency ◽  
Peak Power Output ◽  
Leg Extension

To investigate how leg preference affects net efficiency (ηnet), we examined central and peripheral hemodynamics, muscle fiber type, activation and force of preferred (PL) and non-preferred (NPL) leg. Our hypothesis was that PL greater efficiency could be explained by adaptations and interactions between central, peripheral factors and force. Fifteen young participants performed single-leg extension exercise at absolute (35W) and relative (50%peak power-output (Wpeak)) workloads with PL and NPL. Oxygen uptake, photoplethysmography, Doppler ultrasound, near-infrared-spectroscopy deoxy-hemoglobin [HHb], integrated electromyography (iEMG), maximal isometric force (MVC), rate of force development (RFD50-100) and muscle biopsies of both vastus lateralis, were studied to assess central and peripheral determinants of ηnet. During exercise executed at 35W, ηnet was 17.5±5.1% and 11.9±2.1% (p<0.01) in NP and NPL respectively, while during exercise at the 50% of Wpeak, was in PL = 18.1±5.1% and in NPL = 12.5±1.9 (p<0.01). The only parameter correlated with ηnet was iEMG which showed an inverse correlation for absolute (r=-0.83 and -0.69 for PL and NPL) and relative workloads (r=-0.92 and -0.79 for PL and NPL). MVC and RFD50-100 were higher in PL than in NPL but not correlated to ηnet. This study identified a critical role of leg preference in the efficiency during single-leg extension exercise. The whole spectrum of the central and peripheral, circulatory and muscular determinants of ηnet did not explain the difference between PL and NPL efficiency. Therefore, the lower muscle activation exhibited by the PL is likely the primary determinant of this physiological phenomenon.

Effects of acute hypoxia on cerebral and muscle oxygenation during incremental exercise

2007 ◽  
Vol 103 (1) ◽  
pp. 177-183 ◽  
Author(s):  
Andrew W. Subudhi ◽  
Andrew C. Dimmen ◽  
Robert C. Roach
Keyword(s):  
Power Output ◽  
Repeated Measures ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Vastus Lateralis ◽  
Acute Hypoxia ◽  
Incremental Exercise ◽  
Muscle Oxygenation ◽  
Peak Power Output ◽  
Vastus Lateralis Muscle

To determine if fatigue at maximal aerobic power output was associated with a critical decrease in cerebral oxygenation, 13 male cyclists performed incremental maximal exercise tests (25 W/min ramp) under normoxic (Norm: 21% FiO2) and acute hypoxic (Hypox: 12% FiO2) conditions. Near-infrared spectroscopy (NIRS) was used to monitor concentration (μM) changes of oxy- and deoxyhemoglobin (Δ[O2Hb], Δ[HHb]) in the left vastus lateralis muscle and frontal cerebral cortex. Changes in total Hb were calculated (Δ[THb] = Δ[O2Hb] + Δ[HHb]) and used as an index of change in regional blood volume. Repeated-measures ANOVA were performed across treatments and work rates (α = 0.05). During Norm, cerebral oxygenation rose between 25 and 75% peak power output {Powerpeak; increased (inc) Δ[O2Hb], inc. Δ[HHb], inc. Δ[THb]}, but fell from 75 to 100% Powerpeak {decreased (dec) Δ[O2Hb], inc. Δ[HHb], no change Δ[THb]}. In contrast, during Hypox, cerebral oxygenation dropped progressively across all work rates (dec. Δ[O2Hb], inc. Δ[HHb]), whereas Δ[THb] again rose up to 75% Powerpeak and remained constant thereafter. Changes in cerebral oxygenation during Hypox were larger than Norm. In muscle, oxygenation decreased progressively throughout exercise in both Norm and Hypox (dec. Δ[O2Hb], inc. Δ [HHb], inc. Δ[THb]), although Δ[O2Hb] was unchanged between 75 and 100% Powerpeak. Changes in muscle oxygenation were also greater in Hypox compared with Norm. On the basis of these findings, it is unlikely that changes in cerebral oxygenation limit incremental exercise performance in normoxia, yet it is possible that such changes play a more pivotal role in hypoxia.

Changes in Skeletal Muscle Oxidative Capacity After a Trail-Running Race

2020 ◽  
Vol 15 (2) ◽  
pp. 278-284
Author(s):  
Nicola Giovanelli ◽  
Lea Biasutti ◽  
Desy Salvadego ◽  
Hailu K. Alemayehu ◽  
Bruno Grassi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxidative Metabolism ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Limb Ischemia ◽  
Oxidative Capacity ◽  
Knee Extension ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Trail Running

Purpose: To evaluate the effects of a trail-running race on muscle oxidative function by measuring pulmonary gas exchange variables and muscle fractional O2 extraction. Methods: Eighteen athletes were evaluated before (PRE) and after (POST) a trail-running competition of 32 or 50 km with 2000 or 3500 m of elevation gain, respectively. During the week before the race, runners performed an incremental uphill running test and an incremental exercise by utilizing a 1-leg knee extension ergometer. The knee extension exercise was repeated after the end of the race. During the knee extension test, the authors measured oxygen uptake () and micromolar changes in deoxygenated hemoglobin (Hb)+myoglobin (Mb) concentrations (Δ[deoxy(Hb+Mb)]) on vastus lateralis with a portable near-infrared spectroscopy. Results: was lower at POST versus PRE (−23.9% [9.0%]; P < .001). at POST was lower than at the same workload at PRE (−8.4% [15.6%]; P < .050). Peak power output and time to exhaustion decreased at POST by −23.7% (14.3%) and −18.3% (11.3%), respectively (P < .005). At POST, the increase of Δ[deoxy(Hb+Mb)] as a function of work rate, from unloaded to peak, was less pronounced (from 20.2% [10.1%] to 64.5% [21.1%] of limb ischemia at PRE to 16.9% [12.7%] to 44.0% [18.9%] at POST). Peak Δ[deoxy(Hb+Mb)] values were lower at POST (by −31.2% [20.5%]; P < .001). Conclusions: Trail running leads to impairment in skeletal muscle oxidative metabolism, possibly related to muscle damage from repeated eccentric contractions. In association with other mechanisms, the impairment of skeletal muscle oxidative metabolism is likely responsible for the reduced exercise capacity and tolerance during and following these races.

scholarly journals Application of Molecular Hydrogen as an Antioxidant in Responses to Ventilatory and Ergogenic Adjustments during Incremental Exercise in Humans

Nutrients ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 459
Author(s):  
Ahad Abdulkarim D. Alharbi ◽  
Naoyuki Ebine ◽  
Satoshi Nakae ◽  
Tatsuya Hojo ◽  
Yoshiyuki Fukuoka
Keyword(s):  
Gas Exchange ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Pulmonary Ventilation ◽  
Blood Gases ◽  
Incremental Exercise ◽  
Double Blind ◽  
O2 Delivery

We investigated effects of molecular hydrogen (H2) supplementation on acid-base status, pulmonary gas exchange responses, and local muscle oxygenation during incremental exercise. Eighteen healthy, trained subjects in a randomized, double-blind, crossover design received H2-rich calcium powder (HCP) (1500 mg/day, containing 2.544 µg/day of H2) or H2-depleted placebo (1500 mg/day) for three consecutive days. They performed cycling incremental exercise starting at 20-watt work rate, increasing by 20 watts/2 min until exhaustion. Breath-by-breath pulmonary ventilation (V˙E) and CO2 output (V˙CO2) were measured and muscle deoxygenation (deoxy[Hb + Mb]) was determined via time-resolved near-infrared spectroscopy in the vastus lateralis (VL) and rectus femoris (RF). Blood gases’ pH, lactate, and bicarbonate (HCO3−) concentrations were measured at rest and 120-, 200-, and 240-watt work rates. At rest, the HCP group had significantly lower V˙E, V˙CO2, and higher HCO3−, partial pressures of CO2 (PCO2) versus placebo. During exercise, a significant pH decrease and greater HCO3− continued until 240-watt workload in HCP. The V˙E was significantly lower in HCP versus placebo, but HCP did not affect the gas exchange status of V˙CO2 or oxygen uptake (V˙O2). HCP increased absolute values of deoxy[Hb + Mb] at the RF but not VL. Thus, HCP-induced hypoventilation would lead to lower pH and secondarily impaired balance between O2 delivery and utilization in the local RF during exercise, suggesting that HCP supplementation, which increases the at-rest antioxidant potential, affects the lower ventilation and pH status during incremental exercise. HPC induced a significantly lower O2 delivery/utilization ratio in the RF but not the VL, which may be because these regions possess inherently different vascular/metabolic control properties, perhaps related to fiber-type composition.

scholarly journals PL-012 Effect of hypoxic resistance training on the regulation of muscle mass and phenotype

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Louise Deldicque ◽  
Olouyomi Gnimassou ◽  
Geoffrey Warnier ◽  
Nicolas Benoit ◽  
Damien Naslain ◽  
...  
Keyword(s):  
Resistance Training ◽  
Muscle Mass ◽  
Molecular Mechanisms ◽  
Near Infrared ◽  
Fiber Type ◽  
Muscle Contractions ◽  
Type I ◽  
Fiber Types ◽  
Leg Extension ◽  
Hypoxic Resistance

Objective Hypoxia is a state of lowered oxygen tension in tissue that can be created by environmental or pathological conditions. Whatever the origin of hypoxia, different tissues will adapt acutely and/or chronically to deal with this reduction in oxygen availability. Hypoxia has recently emerged as a particularly efficient stimulus to stimulate muscle cell proliferation and accretion of muscle mass and hypoxic resistance training has become popular amongst athletes as it is thought to favor muscle accretion. However, the molecular mechanisms are largely unknown.  Methods To determine those molecular mechanisms, 19 volunteers participated to 12 sessions of resistance training spread over 4 weeks whether in normoxia (n=9) or in hypoxia (n=10, FiO213.5% corresponding to 3500m altitude). Each session consisted in 6 sets of 10 repetitions of a one-leg extension exercise at 80% of one repetition maximum (1-RM). Blood and muscle samples in each leg were taken before and after the 4-week training period. Fiber types were determined by immunohistochemistry based on myosin heavy chain isotypes. Blood saturation (SpO2, pulsoximetry) and tissue saturation index (TSI, near-infrared spectroscopy) were monitored during the exercise sessions.  Results Muscle thickness determined by ultrasound was increased by 7% in normoxia only (p=0.04). The 1-RM was increased in both groups but the increase was higher in hypoxia (+34%) than in normoxia (+24%) (p=0.02). In average, SpO2stayed around 98-99% in normoxia and around 93-94% in hypoxia during each set of contractions. No difference in TSI between normoxia and hypoxia was measured, which averaged 60% before starting muscle contractions and 40% during muscle contractions. A trend towards a shift in fiber type from type I to type IIa was observed in normoxia (p<0.09) but not in hypoxia. Fiber area was not modified by any condition.  Conclusions In summary, 4 weeks of hypoxic resistance training induced a larger increase in 1-RM compared to normoxic resistance training, independently of muscle hypertrophy or any change in fiber type. Further investigation should determine whether metabolic or molecular changes may explain this potentiation of maximal muscle force by hypoxia.

Muscle Activity Determined by Cosine Tuning With a Nontrivial Preferred Direction During Isometric Force Exertion by Lower Limb

2005 ◽  
Vol 93 (5) ◽  
pp. 2614-2624 ◽  
Author(s):  
Daichi Nozaki ◽  
Kimitaka Nakazawa ◽  
Masami Akai
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Isometric Force ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Joint Torque ◽  
Emg Activity ◽  
Preferred Direction ◽  
Activation Level ◽  
Ankle Brace

We investigated how the CNS selects a unique muscle activation pattern under a redundant situation resulting from the existence of bi-articular muscles. Surface electromyographic (EMG) activity was recorded from eight lower limb muscles while 11 subjects were exerting isometric knee and hip joint torque simultaneously ( Tk and Th, respectively. Extension torque was defined as positive). The knee joint was kept at either 90 or 60°. Various combinations of torque were imposed on both joints by pulling a cable attached to an ankle brace with approximately three levels of isometric force in 16 directions. The distribution of the data in the three-dimensional plot (muscle activation level quantified by the root mean squared value of EMG vs. Tk and Th) demonstrates that the muscle activation level M can be approximated by a single model as M = ⌊ aTk + bTh⌋ where ⌊ x⌋ = max ( x,0) and a and b are constants. The percentage of variance explained by this model averaged over all muscles was 82.3 ± 14.0% (mean ± SD), indicating that the degree of fit of the data to the plane was high. This model suggests that the CNS uses a cosine tuning function on the torque plane ( Tk, Th) to recruit muscles. Interestingly, the muscle's preferred direction (PD) defined as the direction where it is maximally active on the torque plane deviated from its own mechanical pulling direction (MD). This deviation was apparent in the mono-articular knee extensor (MD = 0°, whereas PD = 14.1 ± 3.7° for vastus lateralis) and in the mono-articular hip extensor (MD = 90°, whereas PD = 53.4 ± 6.4° for gluteus maximus). Such misalignment between MD and PD indicates that the mono-articular muscle's activation level depends on the torque of the joint that it does not span. Practical implications of this observation for the motor control studies were discussed. We also demonstrated that the observed shift from the MD to the PD is plausible in the configuration of our musculo-skeletal system and that the experimental results are likely to be explained by the CNS process to minimize the variability of the endpoint force vector under the existence of signal-dependent noise.

scholarly journals The relationship between muscle deoxygenation and activation in different muscles of the quadriceps during cycle ramp exercise

2011 ◽  
Vol 111 (5) ◽  
pp. 1259-1265 ◽  
Author(s):  
Lisa M. K. Chin ◽  
John M. Kowalchuk ◽  
Thomas J. Barstow ◽  
Narihiko Kondo ◽  
Tatsuro Amano ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Near Infrared ◽  
Vastus Lateralis ◽  
Young Male ◽  
Rectus Femoris ◽  
Work Rate ◽  
Sigmoid Function ◽  
Muscle Deoxygenation ◽  
Ramp Exercise ◽  
The Relationship

The relationship between muscle deoxygenation and activation was examined in three different muscles of the quadriceps during cycling ramp exercise. Seven young male adults (24 ± 3 yr; mean ± SD) pedaled at 60 rpm to exhaustion, with a work rate (WR) increase of 20 W/min. Pulmonary oxygen uptake was measured breath-by-breath, while muscle deoxygenation (HHb) and activity were measured by time-resolved near-infrared spectroscopy (NIRS) and surface electromyography (EMG), respectively, at the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). Muscle deoxygenation was corrected for adipose tissue thickness and normalized to the amplitude of the HHb response, while EMG signals were integrated (iEMG) and normalized to the maximum iEMG determined from maximal voluntary contractions. Muscle deoxygenation and activation were then plotted as a percentage of maximal work rate (%WRmax). The HHb response for all three muscle groups was fitted by a sigmoid function, which was determined as the best fitting model. The c/d parameter for the sigmoid fit (representing the %WRmax at 50% of the total amplitude of the HHb response) was similar between VL (47 ± 12% WRmax) and VM (43 ± 11% WRmax), yet greater ( P < 0.05) for RF (65 ± 13% WRmax), demonstrating a “right shift” of the HHb response compared with VL and VM. The iEMG also showed that muscle activation of the RF muscle was lower ( P < 0.05) compared with VL and VM throughout the majority of the ramp exercise, which may explain the different HHb response in RF. Therefore, these data suggest that the sigmoid function can be used to model the HHb response in different muscles of the quadriceps; however, simultaneous measures of muscle activation are also needed for the HHb response to be properly interpreted during cycle ramp exercise.

Muscle Oxygenation Rather Than VO2max as a Strong Predictor of Performance in Sprint Canoe–Kayak

2018 ◽  
Vol 13 (10) ◽  
pp. 1299-1307 ◽  
Author(s):  
Myriam Paquette ◽  
François Bieuzen ◽  
François Billaut
Keyword(s):  
Latissimus Dorsi ◽  
Near Infrared ◽  
Biceps Brachii ◽  
Vastus Lateralis ◽  
Strong Predictor ◽  
Time Trial ◽  
Muscle Oxygenation ◽  
Peak Power Output ◽  
Large Correlation ◽  
And Performance

Purpose: To characterize the relationships between muscle oxygenation and performance during on- and off-water tests in highly trained sprint canoe–kayak athletes. Methods: A total of 30 athletes (19 kayakers and 11 canoeists) performed a maximal incremental test on a canoe or kayak ergometer for determination of VO2max and examination of the relation between peak power output (PPO) and physiological parameters. A subset of 21 athletes also performed a 200- and a 500- (for women) or 1000-m (for men) on-water time trial (TT). Near-infrared spectroscopy monitors were placed on the latissimus dorsi, biceps brachii, and vastus lateralis during all tests to assess changes in muscle O2 saturation (SmO2) and deoxyhemoglobin concentration ([HHb]). The minimum O2 oxygenation (SmO2min) and maximal O2 (Δ[HHb] extraction) were calculated for all subjects. Results: PPO was most strongly correlated with VO2max (R = .9), but there was also a large correlation between PPO and both SmO2min and Δ[HHb] in latissimus dorsi (R = −.5, R = .6) and vastus lateralis (R = −.6, R = .6, all P < .05). Multiple regression showed that 90% of the variance in 200-m performance was explained by both Δ[HHb] and SmO2min in the 3 muscles combined (P < .01) and 71% of the variance in 500-/1000-m performance was explained by Δ[HHb] in the 3 muscles (P < .01). This suggests that O2 extraction is a better predictor of performance than VO2max in sprint canoe–kayak. Conclusions: These results highlight the importance of peripheral adaptations in both short and long events and stress the relevance of adding muscle oxygenation measurements during testing and racing in sprint canoe–kayak.

Observations on force enhancement in submaximal voluntary contractions of human adductor pollicis muscle

2005 ◽  
Vol 98 (6) ◽  
pp. 2087-2095 ◽  
Author(s):  
Ali E. Oskouei ◽  
Walter Herzog
Keyword(s):  
Steady State ◽  
Muscle Activation ◽  
Isometric Force ◽  
Fiber Type ◽  
Voluntary Contraction ◽  
Adductor Pollicis ◽  
Postactivation Potentiation ◽  
Force Enhancement ◽  
Adductor Pollicis Muscle ◽  
Voluntary Contractions

It has been observed consistently and is well accepted that the steady-state isometric force after active muscle stretch is greater than the corresponding isometric force for electrically stimulated muscles and maximal voluntary contractions. However, this so-called force enhancement has not been studied for submaximal voluntary efforts; therefore, it is not known whether this property affects everyday movements. The purpose of this study was to determine whether there was force enhancement during submaximal voluntary contractions. Human adductor pollicis muscles ( n = 17) were studied using a custom-built dynamometer, and both force and activation were measured while muscle activation and force were controlled at a level of 30% of maximal voluntary contraction. The steady-state isometric force and activation after active stretch were compared with the corresponding values obtained during isometric reference contractions. There was consistent and reliable force enhancement in 8 of the 17 subjects, whereas there was no force enhancement in the remaining subjects. Subjects with force enhancement had greater postactivation potentiation and a smaller resistance to fatigue in the adductor pollicis. We conclude from these results that force enhancement exists during submaximal voluntary contractions in a subset of the populations and suggest that it may affect everyday voluntary movements in this subset. On the basis of follow-up testing, it appears that force enhancement during voluntary contractions is linked to potentiation and fatigue resistance and therefore possibly to the fiber-type distribution in the adductor pollicis muscle.

scholarly journals Electrically and hybrid-induced muscle activations: effects of muscle size and fiber type

2016 ◽  
Vol 26 (3) ◽  
Author(s):  
Kelly Stratton ◽  
Pouran D. Faghri
Keyword(s):  
Electrical Activity ◽  
Muscle Activation ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Voluntary Activation ◽  
Muscle Size ◽  
Muscle Coordination ◽  
Abductor Pollicis Brevis ◽  
Informed Consent Form

The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles’ responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG.

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