Muscle length matters: new insights into the neural control of lengthening muscle actions of the knee extensors

Behrens, Martin

doi:10.1113/ep086631

Cited by 4 publications

(4 citation statements)

References 5 publications

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“…Participants visited the laboratory on one occasion and performed a series of submaximal and maximal isometric contractions in two exercise modalities, unilateral isometric knee extension (KE) and bilateral isometric squat (IS), with both conditions matched for hip and knee angle (90 deg) to avoid muscle length‐related differences in neural recruitment (Behrens, ; Doguet et al ., ). Participants were familiarized with the study procedures immediately before data collection, including habituation with performing IS and KE exercise and receiving TMS during submaximal contractions.…”

Section: Methodsmentioning

confidence: 99%

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Brownstein

Ansdell

Škarabot

et al. 2018

Experimental Physiology

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It has been suggested that task-specific changes in neurophysiological function (neuroplasticity) should be assessed using testing modalities that replicate the characteristics of the intervention. The squat is a commonly prescribed resistance exercise that has been shown to elicit changes in CNS function. However, previous studies have assessed squat-induced neuroplasticity using isometric knee extension, potentially confounding the results. The aim of the present study was to assess the agreement between corticospinal and intracortical activity relating to the knee extensors during isometric knee extension compared with an isometric squat task. Eleven males completed a neurophysiological assessment in an isometric squat (IS) and knee-extension (KE) task matched for joint angles (hip, knee and ankle). Single- and paired-pulse transcranial magnetic stimulation was delivered during isometric contractions at a range of intensities to assess short-interval cortical inhibition (SICI) and corticospinal excitability. Group mean values for SICI (70 ± 14 versus 63 ± 12% of unconditioned motor evoked potential during IS and KE, respectively) and corticospinal excitability (mean differences 2-5% of the maximal compound muscle action potential at 25, 50, 75 and 100% maximal voluntary contraction between the IS and KE) were not different between the two tasks (P > 0.05) in the vastus lateralis. However, limits of agreement were wide, with poor-to-moderate average intraclass correlation coefficients (ICCs) (SICI, ICC = 0.15; corticospinal excitability, average ICC range = 0.0-0.63), indicating disparate corticospinal and intracortical activity between the IS and KE. These data highlight the importance of task specificity when assessing the modulation of corticospinal excitability and SICI in response to interventions resulting in neuroplastic changes.

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Section: Methodsmentioning

confidence: 99%

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Brownstein

Ansdell

Škarabot

et al. 2018

Experimental Physiology

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“…Similarly, reductions in RMS EMG activity of RF, VL and SOL reportedly occurred following four variableintensity, short-duration (2 × 1-1.5 min) submaximal ECC cycling sessions (Clos and Lepers, 2020). Reduced lower leg muscle activity in RF, VL and SOL has been linked to adaptations occurring from the repeated bout effect (Clos and Lepers, 2020) that selectively reduces specific motor unit activity (Enoka, 1996;McHugh, 2003), possibly through increased spinal inhibition during ECC contractions (Behrens, 2017). This explanation may well account for the improved muscle activation patterns observed in the current study.…”

Section: Discussionmentioning

confidence: 96%

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling

et al. 2022

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Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18–51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5–0.75) to good (ICC = 0.75–0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70–0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ214 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

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“…To a certain extent therefore, our results that certain individuals increased (significantly so) in global CSE within the ECC cycling condition would not support the premise in the Introduction that eccentric muscle contractions are not associated with a facilitation of CSE. This may have occurred through the known inhibition of Ia afferents, as well as recurrent inhibition to regulate gain at the spinal level 20,21,44 . However, the lack of measurement techniques employed in the present study that may have eluded to sub-cortical or spinal mechanisms at play limits any interpretation of the mechanisms that may have contributed to changes in global CSE following ECC cycling in the current study.…”

Section: Discussionmentioning

confidence: 99%

Global Corticospinal Excitability as Assessed in A Non-Exercised Upper Limb Muscle Compared Between Concentric and Eccentric Modes of Leg Cycling

Walsh

Shemmell

Lepers

et al. 2019

Sci Rep

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This study investigated the effects of eccentric (ECC) and concentric (CON) semi-recumbent leg cycling on global corticospinal excitability (CSE), assessed through the activity of a non-exercised hand muscle. Thirteen healthy male adults completed two 30-min bouts of moderate intensity ECC and CON recumbent cycling on separate days. Power output (POutput), heart rate (HR) and cadence were monitored during cycling. Global CSE was assessed using transcranial magnetic stimulation to elicit motor-evoked potentials (MEP) in the right first dorsal interosseous muscle before (‘Pre’), interleaved (at 10 and 20 mins, t10 and t20, respectively), immediately after (post, P0), and 30-min post exercise (P30). Participants briefly stopped pedalling (no more than 60 s) while stimulation was applied at the t10 and t20 time-points of cycling. Mean POutput, and rate of perceived exertion (RPE) did not differ between ECC and CON cycling and HR was significantly lower during ECC cycling (P = 0.01). Group mean MEP amplitudes were not significantly different between ECC and CON cycling at P0, t10, t20, and P30 and CON (at P > 0.05). Individual participant ratios of POutput and MEP amplitude showed large variability across the two modes of cycling, as did changes in slope of stimulus-response curves. These results suggest that compared to ‘Pre’ values, group mean CSE is not significantly affected by low-moderate intensity leg cycling in both modes. However, POutput and CSE show wide inter-participant variability which has implications for individual neural responses to CON and ECC cycling and rates of adaptation to a novel (ECC) mode. The study of CSE should therefore be analysed for each participant individually in relation to relevant physiological variables and account for familiarisation to semi-recumbent ECC leg cycling.

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Muscle length matters: new insights into the neural control of lengthening muscle actions of the knee extensors

Cited by 4 publications

References 5 publications

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Motor cortical and corticospinal function differ during an isometric squat compared with isometric knee extension

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling

Global Corticospinal Excitability as Assessed in A Non-Exercised Upper Limb Muscle Compared Between Concentric and Eccentric Modes of Leg Cycling

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