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The Magnitude of Peripheral Muscle Fatigue Induced by High and Low Intensity Single-Joint Exercise Does Not Lead to Central Motor Output Reductions in Resistance Trained Men.

Marshall PW, Finn HT, Siegler JC - PLoS ONE (2015)

Bottom Line: Greater reductions in maximal torque and rate of torque development were observed during the 40% protocol (p<0.05).Maximal central motor output did not change for either protocol.For the 40% protocol reductions from pre-exercise in rate and amplitude variables calculated from the Q.(pot.tw) between 66.2 to 70.8% (p<0.001) exceeded those observed during the 80% protocol (p<0.01).

View Article: PubMed Central - PubMed

Affiliation: Human Performance Laboratory, School of Science and Health, University of Western Sydney, Sydney, Australia.

ABSTRACT

Purpose: To examine quadriceps muscle fatigue and central motor output during fatiguing single joint exercise at 40% and 80% maximal torque output in resistance trained men.

Method: Ten resistance trained men performed fatiguing isometric knee extensor exercise at 40% and 80% of maximal torque output. Maximal torque, rate of torque development, and measures of central motor output and peripheral muscle fatigue were recorded at two matched volumes of exercise, and after a final contraction performed to exhaustion. Central motor output was quantified from changes in voluntary activation, normalized surface electromyograms (EMG), and V-waves. Quadriceps muscle fatigue was assessed from changes in the size and shape of the resting potentiated twitch (Q.(pot.tw)). Central motor output during the exercise protocols was estimated from EMG and interpolated twitches applied during the task (VA(sub)).

Results: Greater reductions in maximal torque and rate of torque development were observed during the 40% protocol (p<0.05). Maximal central motor output did not change for either protocol. For the 40% protocol reductions from pre-exercise in rate and amplitude variables calculated from the Q.(pot.tw) between 66.2 to 70.8% (p<0.001) exceeded those observed during the 80% protocol (p<0.01). V-waves only declined during the 80% protocol between 56.8 ± 35.8% to 53.6 ± 37.4% (p<0.05). At the end of the final 80% contraction VA(sub) had increased from 91.2 ± 6.2% to 94.9 ± 4.7% (p = 0.005), but a greater increase was observed during the 40% contraction where VA(sub) had increased from 67.1 ± 6.1% to 88.9 ± 9.6% (p<0.001).

Conclusion: Maximal central motor output in resistance trained men is well preserved despite varying levels of peripheral muscle fatigue. Upregulated central motor output during the 40% contraction protocol appeared to elicit greater peripheral fatigue. V-waves declines during the 80% protocol suggest intensity dependent modulation of the Ia afferent pathway.

No MeSH data available.


Related in: MedlinePlus

Rate of rise in vastus lateralis (VL) and vastus medialis (VM) electromyograms in time intervals from contraction onset.Pooled results from both protocols are displayed. No time, protocol, or interaction effects were observed. Data are mean and SD.
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pone.0140108.g006: Rate of rise in vastus lateralis (VL) and vastus medialis (VM) electromyograms in time intervals from contraction onset.Pooled results from both protocols are displayed. No time, protocol, or interaction effects were observed. Data are mean and SD.

Mentions: No main effects of time, or interaction between time and protocol, were observed for VA (Fig 3), EMG/M (Fig 5), and rate of rise in EMG (Fig 6) variables measured during the maximal contractions. An interaction between time and protocol was observed for reductions in VM and VL V-waves (Figs 2 and 5; p<0.05). No changes were observed for V-waves during the 40% protocol. V-waves during the 80% protocol were reduced from pre-exercise after the final contraction for VM and VL by 56.8 ± 35.8% and 53.6 ± 37.4% respectively (p<0.05).


The Magnitude of Peripheral Muscle Fatigue Induced by High and Low Intensity Single-Joint Exercise Does Not Lead to Central Motor Output Reductions in Resistance Trained Men.

Marshall PW, Finn HT, Siegler JC - PLoS ONE (2015)

Rate of rise in vastus lateralis (VL) and vastus medialis (VM) electromyograms in time intervals from contraction onset.Pooled results from both protocols are displayed. No time, protocol, or interaction effects were observed. Data are mean and SD.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595208&req=5

pone.0140108.g006: Rate of rise in vastus lateralis (VL) and vastus medialis (VM) electromyograms in time intervals from contraction onset.Pooled results from both protocols are displayed. No time, protocol, or interaction effects were observed. Data are mean and SD.
Mentions: No main effects of time, or interaction between time and protocol, were observed for VA (Fig 3), EMG/M (Fig 5), and rate of rise in EMG (Fig 6) variables measured during the maximal contractions. An interaction between time and protocol was observed for reductions in VM and VL V-waves (Figs 2 and 5; p<0.05). No changes were observed for V-waves during the 40% protocol. V-waves during the 80% protocol were reduced from pre-exercise after the final contraction for VM and VL by 56.8 ± 35.8% and 53.6 ± 37.4% respectively (p<0.05).

Bottom Line: Greater reductions in maximal torque and rate of torque development were observed during the 40% protocol (p<0.05).Maximal central motor output did not change for either protocol.For the 40% protocol reductions from pre-exercise in rate and amplitude variables calculated from the Q.(pot.tw) between 66.2 to 70.8% (p<0.001) exceeded those observed during the 80% protocol (p<0.01).

View Article: PubMed Central - PubMed

Affiliation: Human Performance Laboratory, School of Science and Health, University of Western Sydney, Sydney, Australia.

ABSTRACT

Purpose: To examine quadriceps muscle fatigue and central motor output during fatiguing single joint exercise at 40% and 80% maximal torque output in resistance trained men.

Method: Ten resistance trained men performed fatiguing isometric knee extensor exercise at 40% and 80% of maximal torque output. Maximal torque, rate of torque development, and measures of central motor output and peripheral muscle fatigue were recorded at two matched volumes of exercise, and after a final contraction performed to exhaustion. Central motor output was quantified from changes in voluntary activation, normalized surface electromyograms (EMG), and V-waves. Quadriceps muscle fatigue was assessed from changes in the size and shape of the resting potentiated twitch (Q.(pot.tw)). Central motor output during the exercise protocols was estimated from EMG and interpolated twitches applied during the task (VA(sub)).

Results: Greater reductions in maximal torque and rate of torque development were observed during the 40% protocol (p<0.05). Maximal central motor output did not change for either protocol. For the 40% protocol reductions from pre-exercise in rate and amplitude variables calculated from the Q.(pot.tw) between 66.2 to 70.8% (p<0.001) exceeded those observed during the 80% protocol (p<0.01). V-waves only declined during the 80% protocol between 56.8 ± 35.8% to 53.6 ± 37.4% (p<0.05). At the end of the final 80% contraction VA(sub) had increased from 91.2 ± 6.2% to 94.9 ± 4.7% (p = 0.005), but a greater increase was observed during the 40% contraction where VA(sub) had increased from 67.1 ± 6.1% to 88.9 ± 9.6% (p<0.001).

Conclusion: Maximal central motor output in resistance trained men is well preserved despite varying levels of peripheral muscle fatigue. Upregulated central motor output during the 40% contraction protocol appeared to elicit greater peripheral fatigue. V-waves declines during the 80% protocol suggest intensity dependent modulation of the Ia afferent pathway.

No MeSH data available.


Related in: MedlinePlus