Contractile history affects sag and boost properties of unfused tetanic contractions in human quadriceps muscles
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ORIGINAL ARTICLE
Contractile history affects sag and boost properties of unfused tetanic contractions in human quadriceps muscles Ian C. Smith1 · Franziska Onasch1 · Katarzyna Kryściak2 · Jan Celichowski2 · Walter Herzog1,3 Received: 7 July 2020 / Accepted: 11 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose A period of extra-efficient force production (“boost”) followed by a decline in force (“sag”) is often observed at the onset of unfused tetanic contractions. We tested the hypothesis that in human muscle boost and sag are diminished in repeated contractions separated by short rest periods and are re-established or enhanced following long rest periods. Methods Two sets of 3 unfused tetanic contractions were evoked in the right quadriceps muscle group of 29 participants via percutaneous stimulation of the femoral nerve. Contractions consisted of 20 pulses evoked at inter-pulse intervals of 1.25 × twitch time to peak torque. Contractions were evoked 5 s apart and sets were evoked 5 min apart. Results The ratio of the angular impulse of pulses 1–10 to the angular impulse of pulses 11–20 was used as the boost indicator. By this metric, boost was higher (P
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