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Your search keyword '"COCHRANE-SNYMAN, KRISTEN C."' showing total 25 results
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1. Offset Loading in a Bilateral Squatting Movement Pattern Influences Ground-Reaction Force and Muscle Activity in the Dominant and Nondominant Limb.

Author

Ottinger, Charlie R., Tufano, James J., Cochrane-Snyman, Kristen C., Gheith, Raad H., and McBride, Jeffrey M.

Subjects
SKELETAL muscle physiology, EXPERIMENTAL design, ANALYSIS of variance, EXTREMITIES (Anatomy), BODY movement, DESCRIPTIVE statistics, WEIGHT lifting, ATHLETIC ability, BIOMECHANICS, ELECTROMYOGRAPHY, GROUND reaction forces (Biomechanics)
Abstract

Purpose: The purpose of this study was to explore whether offset loading in the barbell squat altered ground-reaction force (GRF) and muscle activation in the dominant (D) and nondominant (ND) lower limb compared to traditional squats. Methods: Twelve well-trained men (age 26.4 [3.2] y; 10.3 [1.9] y experience) performed 3 sets of 10 repetitions at 60% of their previously measured 1-repetition maximum. Sets were quasi-randomized between traditional loading (TDL), dominant-side offset loading (OS-D), and nondominant-side offset loading (OS-ND). All repetitions were performed on a dual force plate with electromyography sensors on the prime mover muscles of the squat. GRF symmetry was assessed using the symmetry index (SI) to determine the direction (D [+] or ND [−]) and magnitude (%) of the asymmetry. Finally, the first 3 and final 3 repetitions of each set were compared for compensatory changes in symmetry. Results: OS-D induced a significant change in limb SI relative to TDL (5.21% vs 1.44%; P =.011); however, no significant difference in limb SI was seen between TDL and OS-ND (−0.66% vs 1.44%; P =.278). No asymmetries between D and ND muscle activation were present in any condition. TDL and OS-D squats exhibited significant improvements in limb SI between the first 3 and final 3 repetitions (P =.035 and.011, respectively); however, no such improvement was seen in OS-ND. Conclusions: OS-D is capable of significantly altering GRF limb SI in a bilateral squat; however, OS-ND appears to exhibit no GRF or electromyography effects relative to TDL. Thus, the results of this study do not support the use of OS-ND in the pursuit of strengthening a weaker limb, suggesting that unilateral training may be a preferred mode of exercise for this desired outcome. [ABSTRACT FROM AUTHOR]

Published
2023
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9. The neuromuscular system

Author

Coburn, Jared W., primary, Beck, Travis W., additional, deVries, Herbert A., additional, Housh, Terry J., additional, Cochrane-Snyman, Kristen C., additional, and Schick, Evan E., additional

Published
2018
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18. Neuromuscular responses of the superficial quadriceps femoris muscles: muscle specific fatigue and inter-individual variability during severe intensity treadmill running

Author

Bergstrom, Haley C., Housh, Terry J., Dinyer, Taylor K., Byrd, M. Travis, Jenkins, Nathaniel D.M., Cochrane-Snyman, Kristen C., Succi, Pasquale J., Schmidt, Richard J., Johnson, Glen O., and Zuniga, Jorge M.

Subjects
Adult, Male, Individual Responses, Electromyography, Superficial Quadriceps, Neuromuscular Junction, Neuromuscular Fatigue, Quadriceps Muscle, Running, Young Adult, Muscle Fatigue, Exercise Test, Humans, Original Article, Female, Critical Velocity, Treadmill Running
Abstract

Objectives: This study examined the time course of changes and patterns of responses in electromyographic amplitude (EMG AMP) and EMG mean power frequency (MPF) for the superficial quadriceps muscles during exhaustive treadmill runs within the severe exercise intensity zones (SIZ1 and SIZ2). Methods: The EMG signals for the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) as well as times to exhaustion (Tlim) were recorded in ten runners during two exhaustive treadmill runs (SIZ1 and SIZ2). The composite and individual responses were compared among muscles and between intensities. Results: The composite patterns of responses in EMG AMP (linear, quadratic, and cubic increases; r2/R2=0.684–0.848) and EMG MPF (linear, quadratic, and cubic decreases; r2/R2=0.648 – 0.852) for the VL and RF were consistent with neuromuscular fatigue in both zones, but those for the VM were not (quadratic, cubic, and non-significant relationships with responses near baseline). The RF tended to demonstrate greater fatigue (EMG MPF decreased from 80–100% Tlim). There was large inter-individual variability (only 10–60% of responses consistent with composite) in response to fatiguing treadmill running. Conclusions: The current findings support the examination and characterization of neuromuscular fatigue on an intensity, muscle, and subject-by-subject basis.

Published
2020

20. Time course of changes in neuromuscular responses during rides to exhaustion above and below critical power

Author

Dinyer, Taylor K., Byrd, M. Travis, Cochrane-Snyman, Kristen C., Jenkins, Nathaniel D.M., Housh, Terry J., Schmidt, Richard J., Johnson, Glen O., and Bergstrom, Haley C.

Subjects
Male, Cycle Ergometry, Exercise Tolerance, Onion Skin Scheme, Electromyography, Electrophysiology, Young Adult, Muscular Wisdom, Muscle Fatigue, Exercise Test, Humans, Original Article, Female, Muscle, Skeletal, Mechanomyography, Muscle Contraction
Abstract

Objectives: To examine the time course of changes in electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) responses during cycle ergometry to exhaustion performed above (CP+10%) and below (CP-10%) critical power (CP) to infer motor unit activation strategies used to maintain power output. Methods: Participants performed a 3-min all out test to determine CP, and 2 randomly ordered, continuous rides to exhaustion at CP+10% and CP-10%. V̇O2, EMG AMP, EMG MPF, MMG AMP, MMG MPF, and time to exhaustion (Tlim) were recorded. Responses at CP-10% and CP+10% were analyzed separately. Results: At CP-10%, EMG and MMG AMP were significantly greater than the initial 5% timepoint at 100% Tlim. EMG MPF and MMG MPF reflected a downward trend that resulted in no significant difference between timepoints. At CP+10%, EMG AMP was significantly greater than the initial 5% timepoint from 60% to 100% Tlim. MMG AMP was less than the initial 5% timepoint at only 50% Tlim. EMG and MMG MPF were significantly less than the initial 5% timepoint at 20% Tlim and 100% Tlim, respectively. Conclusions: The time-course of changes in EMG and MMG signals were different at CP-10% and CP+10%, but responses observed indicated cycle ergometry to exhaustion relies on similar motor unit activation strategies.

Published
2019

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