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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

Overview of the experimental protocol used in this study.Maximal voluntary torque was measured pre-exercise, after VOL–1, VOL–2, and the end of the final contraction performed to exhaustion.
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pone.0140108.g001: Overview of the experimental protocol used in this study.Maximal voluntary torque was measured pre-exercise, after VOL–1, VOL–2, and the end of the final contraction performed to exhaustion.

Mentions: The 80% exercise protocol required 60s of total contraction time. This was divided into two 30s contractions, with 1-min rest (Fig 1). Pilot work found that 30s was the highest multiple of 10 that could be sustained by similarly trained participants without failure for an initial contraction. 1-min rest was determined as the minimum rest period where participants were able to recover sufficiently to reach the 80% torque level again. MVT was measured immediately after 30s and 60s. The 40% protocol required 120s of total contraction time. To allow comparisons between-protocols after matched exercise volumes, MVT was measured at 60s (VOL–1) and 120s (VOL–2) during the 40% protocol, with 1-min rest provided after each maximal effort.


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)

Overview of the experimental protocol used in this study.Maximal voluntary torque was measured pre-exercise, after VOL–1, VOL–2, and the end of the final contraction performed to exhaustion.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0140108.g001: Overview of the experimental protocol used in this study.Maximal voluntary torque was measured pre-exercise, after VOL–1, VOL–2, and the end of the final contraction performed to exhaustion.
Mentions: The 80% exercise protocol required 60s of total contraction time. This was divided into two 30s contractions, with 1-min rest (Fig 1). Pilot work found that 30s was the highest multiple of 10 that could be sustained by similarly trained participants without failure for an initial contraction. 1-min rest was determined as the minimum rest period where participants were able to recover sufficiently to reach the 80% torque level again. MVT was measured immediately after 30s and 60s. The 40% protocol required 120s of total contraction time. To allow comparisons between-protocols after matched exercise volumes, MVT was measured at 60s (VOL–1) and 120s (VOL–2) during the 40% protocol, with 1-min rest provided after each maximal effort.

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