Thigh muscle activation distribution and pulmonary V̇o2 kinetics during moderate, heavy, and very heavy intensity cycling exercise in humans

2007 ◽  
Vol 293 (2) ◽  
pp. R812-R820 ◽  
Author(s):  
Masako Yamaoka Endo ◽  
Mayumi Kobayakawa ◽  
Ryuta Kinugasa ◽  
Shinya Kuno ◽  
Hiroshi Akima ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Slow Component ◽  
Transverse Relaxation Time ◽  
Magnetic Resonance Images ◽  
Thigh Muscle ◽  
Moderate Exercise ◽  
Muscle Recruitment ◽  
Heavy Exercise ◽  
Leg Muscles ◽  
Muscle Activation Patterns

The mechanisms underlying the oxygen uptake (V̇o2) slow component during supra-lactate threshold (supra-LT) exercise are poorly understood. Evidence suggests that the V̇o2 slow component may be caused by progressive muscle recruitment during exercise. We therefore examined whether leg muscle activation patterns [from the transverse relaxation time (T2) of magnetic resonance images] were associated with supra-LT V̇o2 kinetic parameters. Eleven subjects performed 6-min cycle ergometry at moderate (80% LT), heavy (70% between LT and critical power; CP), and very heavy (7% above CP) intensities with breath-by-breath pulmonary V̇o2 measurement. T2 in 10 leg muscles was evaluated at rest and after 3 and 6 min of exercise. During moderate exercise, nine muscles achieved a steady-state T2 by 3 min; only in the vastus medialis did T2 increase further after 6 min. During heavy exercise, T2 in the entire vastus group increased between minutes 3 and 6, and additional increases in T2 were seen in adductor magnus and gracilis during this period of very heavy exercise. The V̇o2 slow component increased with increasing exercise intensity (being functionally zero during moderate exercise). The distribution of T2 was more diverse as supra-LT exercise progressed: T2 variance (ms) increased from 3.6 ± 0.2 to 6.5 ± 1.7 between 3 and 6 min of heavy exercise and from 5.5 ± 0.8 to 12.3 ± 5.4 in very heavy exercise (rest = 3.1 ± 0.6). The T2 distribution was significantly correlated with the magnitude of the V̇o2 slow component ( P < 0.05). These data are consistent with the notion that the V̇o2 slow component is an expression of progressive muscle recruitment during supra-LT exercise.

scholarly journals A method for detecting the temporal sequence of muscle activation during cycling using MRI

2011 ◽  
Vol 110 (3) ◽  
pp. 826-833 ◽  
Author(s):  
Christopher P. Elder ◽  
Ryan N. Cook ◽  
Kenneth L. Wilkens ◽  
Marti A. Chance ◽  
Otto A. Sanchez ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Transverse Relaxation Time ◽  
Biceps Femoris ◽  
Cycle Ergometer ◽  
Muscle Recruitment ◽  
Spatial And Temporal Patterns ◽  
Variable Loading ◽  
Limited Applicability ◽  
The Difference ◽  
Long Head

Surface electromyography (EMG) can assess muscle recruitment patterns during cycling, but has limited applicability to studies of deep muscle recruitment and electrically stimulated contractions. We determined whether muscle recruitment timing could be inferred from MRI-measured transverse relaxation time constant (T2) changes and a cycle ergometer modified to vary power as a function of pedal angle. Six subjects performed 6 min of single-leg cycling under two conditions (E0°-230° and E90°-230°), which increased the power from 0°-230° and 90–230° of the pedal cycle, respectively. The difference condition produced a virtual power output from 0–180° (V0°-180°). Recruitment was assessed by integrating EMG over the pedal cycle (IEMG) and as the (post-pre) exercise T2 change (ΔT2). For E0°-230°, the mean IEMG for vastus medialis and lateralis (VM/VL; 49.3 ± 3.9 mV·s; mean ± SE) was greater ( P < 0.05) than that for E90°-230° (17.9 ± 1.9 mV·s); the corresponding ΔT2 values were 8.7 ± 1.0 and 1.4 ± 0.5 ms ( P < 0.05). For E0°-230° and E90°-230°, the IEMG values for biceps femoris/long head (BFL) were 37.7 ± 5.4 and 27.1 ± 5.6 mV·s ( P > 0.05); the corresponding ΔT2 values were 0.9 ± 0.9 and 1.5 ± 0.9 ms ( P > 0.05). MRI data indicated activation of the semitendinosus and BF/short head for E0°-230° and E90°-230°. For V0°-180°, ΔT2 was 7.2 ± 0.9 ms for VM/VL and −0.6 ± 0.6 ms for BFL; IEMG was 31.5 ± 3.7 mV·s for VM/VL and 10.6 ± 7.0 mV·s for BFL. MRI and EMG data indicate VM/VL activity from 0 to 180° and selected hamstring activity from 90 to 230°. Combining ΔT2 measurements with variable loading allows the spatial and temporal patterns of recruitment during cycling to be inferred from MRI data.

scholarly journals Effects of Short-Term Training With Uncoupled Cranks in Trained Cyclists

2012 ◽  
Vol 7 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Jack M. Burns ◽  
Jeremiah J. Peiffer ◽  
Chris R. Abbiss ◽  
Greig Watson ◽  
Angus Burnett ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Biceps Femoris ◽  
Training Group ◽  
Recovery Phase ◽  
Muscle Recruitment ◽  
Short Term ◽  
Activation Patterns ◽  
Gross Efficiency ◽  
Muscle Activation Patterns

Purpose:Manufacturers of uncoupled cycling cranks claim that their use will increase economy of motion and gross efficiency. Purportedly, this occurs by altering the muscle-recruitment patterns contributing to the resistive forces occurring during the recovery phase of the pedal stroke. Uncoupled cranks use an independent-clutch design by which each leg cycles independently of the other (ie, the cranks are not fixed together). However, research examining the efficacy of training with uncoupled cranks is equivocal. The purpose of this study was to determine the effect of short-term training with uncoupled cranks on the performance-related variables economy of motion, gross efficiency, maximal oxygen uptake (VO2max), and muscle-activation patterns.Methods:Sixteen trained cyclists were matched-paired into either an uncoupled-crank or a normal-crank training group. Both groups performed 5 wk of training on their assigned cranks. Before and after training, participants completed a graded exercise test using normal cranks. Expired gases were collected to determine economy of motion, gross efficiency, and VO2max, while integrated electromyography (iEMG) was used to examine muscle-activation patterns of the vastus lateralis, biceps femoris, and gastrocnemius.Results:No significant changes between groups were observed for economy of motion, gross efficiency, VO2max, or iEMG in the uncoupled- or normal-crank group.Conclusions:Five weeks of training with uncoupled cycling cranks had no effect on economy of motion, gross efficiency, muscle recruitment, or VO2max compared with training on normal cranks.

scholarly journals Stability of Measurement Outcomes for Voluntary Task Performance in Participants With Chronic Ankle Instability and Healthy Participants

2011 ◽  
Vol 46 (4) ◽  
pp. 366-375 ◽  
Author(s):  
Sara Van Deun ◽  
Karel Stappaerts ◽  
Oron Levin ◽  
Luc Janssens ◽  
Filip Staes
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Intervention Program ◽  
Ankle Instability ◽  
Chronic Ankle Instability ◽  
Control Group ◽  
Muscle Recruitment ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Recruitment Order

Context: Acceptable measurement stability during data collection is critically important to research. To interpret differences in measurement outcomes among participants or changes within participants after an intervention program, we need to know whether the measurement is stable and consistent. Objective: To determine the within-session stability of muscle activation patterns for a voluntary postural-control task in a group of noninjured participants and a group of participants with chronic ankle instability (CAI). Design: Descriptive laboratory study. Setting: Musculoskeletal laboratory. Patients or Other Participants: Twenty control participants (8 men, 12 women; age = 21.8 ± 2.4 years, height = 164.3 ± 13.4 cm, mass = 68.4 ± 17.9 kg) and 20 participants with CAI (12 men, 8 women; age = 21.2 ± 2.1 years, height = 176 ± 10.2 cm, mass = 71.7 ± 11.3 kg). Intervention(s): Participants performed 4 barefoot standing trials, each of which included a 30-second double-legged stance followed by a 30-second single-legged stance in 3 conditions: with vision, without vision, and with vision on a balance pad. Main Outcome Measure(s): The activity of 7 muscles of the lower limb was measured for the stance task in the 3 different conditions for each trial. The onset of muscle activity and muscle recruitment order were determined and compared between the first and the fourth trials for both groups and for each condition. Results: We found no differences in the onset of muscle activity among trials for both groups or for each condition. The measurement error was 0.9 seconds at maximum for the control group and 0.12 seconds for the CAI group. In the control group, 70% to 80% of the participants used the same muscle recruitment order in both trials. In the CAI group, 75% to 90% used the same recruitment order. Conclusions: Within 1 session, measurement stability for this task was acceptable for use in further research. Furthermore, no differences were found in measurement stability across conditions in the control or CAI groups.

A Computational Model of Muscle Recruitment for Wrist Movements

2002 ◽  
Vol 88 (6) ◽  
pp. 3348-3358 ◽  
Author(s):  
Andrew H. Fagg ◽  
Ashvin Shah ◽  
Andrew G. Barto
Keyword(s):  
Motor System ◽  
Muscle Activation ◽  
Movement Direction ◽  
Joint Motion ◽  
Muscle Recruitment ◽  
Task Constraints ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
Recruitment Behavior ◽  
Total Effort

To execute a movement, the CNS must appropriately select and activate the set of muscles that will produce the desired movement. This problem is particularly difficult because a variety of muscle subsets can usually be used to produce the same joint motion. The motor system is therefore faced with a motor redundancy problem that must be resolved to produce the movement. In this paper, we present a model of muscle recruitment in the wrist step-tracking task. Muscle activation levels for five muscles are selected so as to satisfy task constraints (moving to the designated target) while also minimizing a measure of the total effort in producing the movement. Imposing these constraints yields muscle activation patterns qualitatively similar to those observed experimentally. In particular, the model reproduces the observed cosine-like recruitment of muscles as a function of movement direction and also appropriately predicts that certain muscles will be recruited most strongly in movement directions that differ significantly from their direction of action. These results suggest that the observed recruitment behavior may not be an explicit strategy employed by the nervous system, but instead may result from a process of movement optimization.

Effect of Fatigue on Single-Leg Hop Landing Biomechanics

2006 ◽  
Vol 22 (4) ◽  
pp. 245-254 ◽  
Author(s):  
Karl F. Orishimo ◽  
Ian J. Kremenic
Keyword(s):  
Muscle Fatigue ◽  
Muscle Activation ◽  
Vastus Lateralis ◽  
Plantar Flexion ◽  
Thigh Muscle ◽  
Functional Improvement ◽  
Compensatory Mechanisms ◽  
Knee Motion ◽  
Muscle Activation Patterns ◽  
Knee Pathology

The objective of this study was to measure adaptations in landing strategy during single-leg hops following thigh muscle fatigue. Kinetic, kinematic, and electromyographic data were recorded as thirteen healthy male subjects performed a single-leg hop in both the unfatigued and fatigued states. To sufficiently fatigue the thigh muscles, subjects performed at least two sets of 50 step-ups. Fatigue was assessed by measuring horizontal hopping ability following the protocol. Joint motion and loading, as well as muscle activation patterns, were compared between fatigued and unfatigued conditions. Fatigue significantly increased knee motion (p = 0.012) and shifted the ankle into a more dorsiflexed position (p = 0.029). Hip flexion was also reduced following fatigue (p = 0.042). Peak extension moment tended to decrease at the knee and increase at the ankle and hip (p = 0.014). Ankle plantar flexion moment at the time of peak total support moment increased from 0.8 (N⋅m)/kg (SD, 0.6 [N⋅m]/kg) to 1.5 (N⋅m)/kg (SD, 0.8 [N⋅m]/kg) (p = 0.006). Decreased knee moment and increased knee flexion during landings following fatigue indicated that the control of knee motion was compromised despite increased activation of the vastus medialis, vastus lateralis, and rectus femoris (p = 0.014, p = 0.014, and p = 0.017, respectively). Performance at the ankle increased to compensate for weakness in the knee musculature and to maintain lower extremity stability during landing. Investigating the biomechanical adaptations that occur in healthy subjects as a result of muscle fatigue may give insight into the compensatory mechanisms and loading patterns occurring in patients with knee pathology. Changes in single-leg hop landing performance could be used to demonstrate functional improvement in patients due to training or physical therapy.

V˙o 2 kinetics in heavy exercise is not altered by prior exercise with a different muscle group

2002 ◽  
Vol 92 (6) ◽  
pp. 2467-2474 ◽  
Author(s):  
Yoshiyuki Fukuba ◽  
Naoyuki Hayashi ◽  
Shunsaku Koga ◽  
Takayoshi Yoshida
Keyword(s):  
Near Infrared ◽  
Slow Component ◽  
Exponential Model ◽  
Muscle Group ◽  
Heavy Exercise ◽  
Arm Cranking ◽  
Warm Up ◽  
Leg Muscles ◽  
Leg Cycling ◽  
Lactic Acidemia

We examined whether lactic acidemia-induced hyperemia at the onset of high-intensity leg exercise contributed to the speeding of pulmonary O2 uptake (V˙o 2) after prior heavy exercise of the same muscle group or a different muscle group (i.e., arm). Six healthy male subjects performed two protocols that consisted of two consecutive 6-min exercise bouts separated by a 6-min baseline at 0 W: 1) both bouts of heavy (work rate: 50% of lactate threshold to maximal V˙o 2) leg cycling (L1-ex to L2-ex) and 2) heavy arm cranking followed by identical heavy leg cycling bout (A1-ex to A2-ex). Blood lactate concentrations before L1-ex, L2-ex, and A2-ex averaged 1.7 ± 0.3, 5.6 ± 0.9, and 6.7 ± 1.4 meq/l, respectively. An “effective” time constant (τ) of V˙o 2 with the use of the monoexponential model in L2-ex (τ: 36.8 ± 4.3 s) was significantly faster than that in L1-ex (τ: 52.3 ± 8.2 s). Warm-up arm cranking did not facilitate theV˙o 2 kinetics for the following A2-ex [τ: 51.7 ± 9.7 s]. The double-exponential model revealed no significant change of primary τ (phase II)V˙o 2 kinetics. Instead, the speeding seen in the effective τ during L2-ex was mainly due to a reduction of theV˙o 2 slow component. Near-infrared spectroscopy indicated that the degree of hyperemia in working leg muscles was significantly higher at the onset of L2-ex than A2-ex. In conclusion, facilitation of V˙o 2 kinetics during heavy exercise preceded by an intense warm-up exercise was caused principally by a reduction in the slow component, and it appears unlikely that this could be ascribed exclusively to systemic lactic acidosis.

Rotator-Cuff Muscle-Recruitment Strategies During Shoulder Rehabilitation Exercises

2011 ◽  
Vol 20 (4) ◽  
pp. 471-486 ◽  
Author(s):  
Kathleen A. Swanik ◽  
Kellie Huxel Bliven ◽  
Charles Buz Swanik
Keyword(s):  
Rotator Cuff ◽  
Muscle Activation ◽  
Glenohumeral Joint ◽  
Neuromuscular Control ◽  
Muscle Recruitment ◽  
Individual Muscle ◽  
Muscle Activation Patterns ◽  
Outcomes Measures ◽  
Rehabilitation Exercises ◽  
Teres Minor

Context:There are contradictory data on optimal muscle-activation strategies for restoring shoulder stability. Further investigation of neuromuscular-control strategies for glenohumeral-joint stability will guide clinicians in decisions regarding appropriate rehabilitation exercises.Objectives:To determine whether subscapularis, infraspinatus, and teres minor (anteroposterior force couple) muscle activation differ between 4 shoulder exercises and describe coactivation ratios and individual muscle-recruitment characteristics of rotator-cuff muscles throughout each shoulder exercise.Design:Crossover.Setting:Laboratory.Participants:healthy, physically active men, age 20.55 ± 2.0 y.Interventions:4 rehabilitation exercises: pitchback, PNF D2 pattern with tubing, push-up plus, and slide board.Main Outcomes Measures:Mean coactivation level, coactivation-ratio patterns, and level (area) of muscle-activation patterns of the subscapularis, infraspinatus, and teres minor throughout each exercise.Results:Coactivation levels varied throughout each exercise. Subscapularis activity was consistently higher than that of the infraspinatus and teres minor combined at the start of each exercise and in end ranges of motion. Individual muscle-recruitment levels in the subscapularis were also different between exercises.Conclusion:Results provide descriptive data for determining normative coactivation-ratio values for muscle recruitment for the functional exercises studied. Differences in subscapularis activation suggest a reliance to resist anteriorly directed forces.

scholarly journals Effects of prior heavy exercise on phase II pulmonary oxygen uptake kinetics during heavy exercise

2000 ◽  
Vol 89 (4) ◽  
pp. 1387-1396 ◽  
Author(s):  
Mark Burnley ◽  
Andrew M. Jones ◽  
Helen Carter ◽  
Jonathan H. Doust
Keyword(s):  
Oxygen Uptake ◽  
Phase Ii ◽  
Slow Component ◽  
Exercise Bout ◽  
Oxygen Uptake Kinetics ◽  
Cycle Ergometer ◽  
Moderate Exercise ◽  
Heavy Exercise ◽  
Mean Response Time ◽  
The Mean

We tested the hypothesis that heavy-exercise phase II oxygen uptake (V˙o 2) kinetics could be speeded by prior heavy exercise. Ten subjects performed four protocols involving 6-min exercise bouts on a cycle ergometer separated by 6 min of recovery: 1) moderate followed by moderate exercise; 2) moderate followed by heavy exercise; 3) heavy followed by moderate exercise; and 4) heavy followed by heavy exercise. The V˙o 2 responses were modeled using two (moderate exercise) or three (heavy exercise) independent exponential terms. Neither moderate- nor heavy-intensity exercise had an effect on the V˙o 2 kinetic response to subsequent moderate exercise. Although heavy-intensity exercise significantly reduced the mean response time in the second heavy exercise bout (from 65.2 ± 4.1 to 47.0 ± 3.1 s; P < 0.05), it had no significant effect on either the amplitude or the time constant (from 23.9 ± 1.9 to 25.3 ± 2.9 s) of theV˙o 2 response in phase II. Instead, this “speeding” was due to a significant reduction in the amplitude of the V˙o 2 slow component. These results suggest phase II V˙o 2 kinetics are not speeded by prior heavy exercise.

scholarly journals Effect of muscle mass on V˙o 2kinetics at the onset of work

2001 ◽  
Vol 90 (2) ◽  
pp. 461-468 ◽  
Author(s):  
Shunsaku Koga ◽  
Thomas J. Barstow ◽  
Tomoyuki Shiojiri ◽  
Tetsuo Takaishi ◽  
Yoshiyuki Fukuba ◽  
...  
Keyword(s):  
Muscle Mass ◽  
Ventilatory Threshold ◽  
Slow Component ◽  
Cycle Ergometer ◽  
Muscle Recruitment ◽  
Heavy Exercise ◽  
Mean Response Time ◽  
Heavy Work ◽  
Exercise Transitions ◽  
Recruitment Patterns

The dependence of O2 uptake (V˙o 2) kinetics on the muscle mass recruited under conditions when fiber and muscle recruitment patterns are similar following the onset of exercise has not been determined. We developed a motorized cycle ergometer that facilitated one-leg (1L) cycling in which the electromyographic (EMG) profile of the active muscles was not discernibly altered from that during two-leg (2L) cycling. Six subjects performed 1L and 2L exercise transitions from unloaded cycling to moderate [<ventilatory threshold (VT)] and heavy (>VT) exercise. The 1L condition yielded kinetics that was unchanged from the 2L condition [the phase 2 time constants (τ1, in s) for <VT were as follows: 1L = 16.8±8.4 (SD), 2L = 18.4 ± 8.1, P > 0.05; for >VT: 1L = 26.8 ± 12.0; 2L = 27.8 ± 16.1, P > 0.05]. The overall V˙o 2 kinetics (mean response time) was not significantly different for the two exercise conditions. However, the gain of the fast component (the amplitude/work rate) during the 1L exercise was significantly higher than that for the 2L exercise for both moderate and heavy work rates. The slow-component responses evident for heavy exercise were temporally and quantitatively unaffected by the 1L condition. These data demonstrate that, when leg muscle recruitment patterns are unchanged as assessed by EMG analysis, on-transient V˙o 2 kinetics for both moderate and heavy exercise are not dependent on the muscle mass recruited.

scholarly journals Oxygen uptake kinetics during treadmill running in boys and men

2001 ◽  
Vol 90 (5) ◽  
pp. 1700-1706 ◽  
Author(s):  
Craig A. Williams ◽  
Helen Carter ◽  
Andrew M. Jones ◽  
Jonathan H. Doust
Keyword(s):  
Oxygen Uptake ◽  
Time Constant ◽  
Slow Component ◽  
Oxygen Uptake Kinetics ◽  
Primary Response ◽  
Treadmill Running ◽  
Initial Increase ◽  
Moderate Exercise ◽  
Heavy Exercise ◽  
The Difference

The purpose of this study was to compare the kinetics of the oxygen uptake (V˙o 2) response of boys to men during treadmill running using a three-phase exponential modeling procedure. Eight boys (11–12 yr) and eight men (21–36 yr) completed an incremental treadmill test to determine lactate threshold (LT) and maximum V˙o 2. Subsequently, the subjects exercised for 6 min at two different running speeds corresponding to 80% of V˙o 2 at LT (moderate exercise) and 50% of the difference betweenV˙o 2 at LT and maximumV˙o 2 (heavy exercise). For moderate exercise, the time constant for the primary response was not significantly different between boys [10.2 ± 1.0 (SE) s] and men (14.7 ± 2.8 s). The gain of the primary response was significantly greater in boys than men (239.1 ± 7.5 vs. 167.7 ± 5.4 ml · kg−1 · km−1; P < 0.05). For heavy exercise, theV˙o 2 on-kinetics were significantly faster in boys than men (primary response time constant = 14.9 ± 1.1 vs. 19.0 ± 1.6 s; P < 0.05), and the primary gain was significantly greater in boys than men (209.8 ± 4.3 vs. 167.2 ± 4.6 ml · kg−1 · km−1; P < 0.05). The amplitude of theV˙o 2 slow component was significantly smaller in boys than men (19 ± 19 vs. 289 ± 40 ml/min; P < 0.05). The V˙o 2responses at the onset of moderate and heavy treadmill exercise are different between boys and men, with a tendency for boys to have faster on-kinetics and a greater initial increase inV˙o 2 for a given increase in running speed.

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