‘SIT’ down and relax: the interpolated twitch technique is still a valid measure of central fatigue during sustained contraction tasks

Arthur J. Cheng; Brian H. Dalton; Brad Harwood; Geoffrey A. Power

doi:10.1113/jphysiol.2013.258566

‘SIT’ down and relax: the interpolated twitch technique is still a valid measure of central fatigue during sustained contraction tasks

The Journal of Physiology ◽

10.1113/jphysiol.2013.258566 ◽

2013 ◽

Vol 591 (15) ◽

pp. 3677-3678 ◽

Cited By ~ 3

Author(s):

Arthur J. Cheng ◽

Brian H. Dalton ◽

Brad Harwood ◽

Geoffrey A. Power

Keyword(s):

Central Fatigue ◽

Valid Measure ◽

Sustained Contraction ◽

Interpolated Twitch Technique

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Unlike voluntary contractions, stimulated contractions of a hand muscle do not reduce voluntary activation or motoneuronal excitability

Journal of Applied Physiology ◽

10.1152/japplphysiol.00553.2019 ◽

2020 ◽

Vol 128 (5) ◽

pp. 1412-1422

Author(s):

J. M. D’Amico ◽

D. M. Rouffet ◽

S. C. Gandevia ◽

J. L. Taylor

Keyword(s):

Central Fatigue ◽

Voluntary Activation ◽

Motoneuron Excitability ◽

Interpolated Twitch Technique ◽

Hand Muscle ◽

Voluntary Contractions

We demonstrate that reductions in voluntary activation and motoneuron excitability following 2-min isometric maximal contractions in humans occur only when fatigue is produced through voluntary contractions and not through electrically stimulated contractions. This is contrary to studies that suggest that changes in the superimposed twitch and therefore voluntary activation are explained by changes in peripheral factors alone. Thus, the interpolated twitch technique remains a viable tool to assess voluntary activation and central fatigue.

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Reliability of Tibialis Anterior Muscle Voluntary Activation Using the Interpolated Twitch Technique and the Central Activation Ratio in People with Stroke

Brain Sciences ◽

10.3390/brainsci11020176 ◽

2021 ◽

Vol 11 (2) ◽

pp. 176

Author(s):

Sharon Olsen ◽

Nada Signal ◽

Imran Khan Niazi ◽

Gemma Alder ◽

Usman Rashid ◽

...

Keyword(s):

Electrical Stimulation ◽

Lower Bound ◽

Tibialis Anterior ◽

Tibialis Anterior Muscle ◽

Central Fatigue ◽

Chronic Stroke ◽

Voluntary Activation ◽

Central Activation Ratio ◽

Interpolated Twitch Technique ◽

Activation Ratio

Voluntary activation (VA) is measured by applying supramaximal electrical stimulation to a muscle during a maximal voluntary contraction (MVC). The amplitude of the evoked muscle twitch is used to determine any VA deficit, and indicates incomplete central neural drive to the motor units. People with stroke experience VA deficits and greater levels of central fatigue, which is the decrease in VA that occurs following exercise. This study investigated the between-session reliability of VA and central fatigue of the tibialis anterior muscle (TA) in people with chronic stroke (n = 12), using the interpolated twitch technique (ITT), adjusted-ITT, and central activation ratio (CAR) methods. On two separate sessions, supramaximal electrical stimulation was applied to the TA when it was at rest and maximally activated, at the start and end of a 30-s isometric dorsiflexor MVC. The most reliable measures of VA were obtained using the CAR calculation on transformed data, which produced an ICC of 0.92, and a lower bound confidence interval in the good range (95% CI 0.77 to 0.98). Reliability was lower for the CAR calculation on non-transformed data (ICC 0.82, 95% CI 0.63 to 0.91) and the ITT and adjusted-ITT calculations on transformed data (ICCs 0.82, 95% CIs 0.51 to 0.94), which had lower bound confidence intervals in the moderate range. The two ITT calculations on non-transformed data demonstrated the poorest reliability (ICCs 0.62, 95% CI 0.25 to 0.74). Central fatigue measures demonstrated very poor reliability. Thus, the reliability for VA in people with chronic stroke ranged from good to poor, depending on the calculation method and statistical analysis method, whereas the reliability for central fatigue was very poor.

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Reduced voluntary drive during sustained but not during brief maximal voluntary contractions in the first dorsal interosseous weakened by spinal cord injury

Journal of Applied Physiology ◽

10.1152/japplphysiol.00399.2015 ◽

2015 ◽

Vol 119 (11) ◽

pp. 1320-1329 ◽

Cited By ~ 3

Author(s):

Roeland F. Prak ◽

Marwah Doestzada ◽

Christine K. Thomas ◽

Marga Tepper ◽

Inge Zijdewind

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Muscle Activation ◽

Spinal Injury ◽

Central Fatigue ◽

First Dorsal Interosseous ◽

Voluntary Muscle ◽

Sustained Contraction ◽

Cord Injury ◽

Voluntary Contractions

In able-bodied (AB) individuals, voluntary muscle activation progressively declines during sustained contractions. However, few data are available on voluntary muscle activation during sustained contractions in muscles weakened by spinal cord injury (SCI), where greater force declines may limit task performance. SCI-related impairment of muscle activation complicates interpretation of the interpolated twitch technique commonly used to assess muscle activation. We attempted to estimate and correct for the SCI-related-superimposed twitch. Seventeen participants, both AB and with SCI (American Spinal Injury Association Impairment Scale C/D) produced brief and sustained (2-min) maximal voluntary contractions (MVCs) with the first dorsal interosseous. Force and electromyography were recorded together with superimposed (doublet) twitches. MVCs of participants with SCI were weaker than those of AB participants (20.3 N, SD 7.1 vs. 37.9 N, SD 9.5; P < 0.001); MVC-superimposed twitches were larger in participants with SCI (SCI median 10.1%, range 2.0-63.2%; AB median 4.7%, range 0.0–18.4% rest twitch; P = 0.007). No difference was found after correction for the SCI-related-superimposed twitch (median 6.7%, 0.0–17.5% rest twitch, P = 0.402). Thus during brief contractions, the maximal corticofugal output that participants with SCI could exert was similar to that of AB participants. During the sustained contraction, force decline (SCI, 58.0%, SD 15.1; AB, 57.2% SD 13.3) was similar ( P = 0.887) because participants with SCI developed less peripheral ( P = 0.048) but more central fatigue than AB participants. The largest change occurred at the start of the sustained contraction when the (corrected) superimposed twitches increased more in participants with SCI (SCI, 16.3% rest twitch, SD 20.8; AB, 2.7%, SD 4.7; P = 0.01). The greater reduction in muscle activation after SCI may relate to a reduced capacity to overcome fast fatigue-related excitability changes at the spinal level.

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