Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, Cleveland, OH, 44106, USA.
Kent State University, 800 E Summit St, Kent, OH, 44240, USA.
J Neuroeng Rehabil. 2022 Aug 9;19(1):85. doi: 10.1186/s12984-022-01064-w.
Stimulation-driven exercise is often limited by rapid fatigue of the activated muscles. Selective neural stimulation patterns that decrease activated fiber overlap and/or duty cycle improve cycling exercise duration and intensity. However, unequal outputs from independently activated fiber populations may cause large discrepancies in power production and crank angle velocity among pedal revolutions. Enforcing a constant cadence through feedback control of stimulus levels may address this issue and further improve endurance by targeting a submaximal but higher than steady-state exercise intensity.
Seven participants with paralysis cycled using standard cadence-controlled stimulation (S-Cont). Four of those participants also cycled with a low duty cycle (carousel) cadence-controlled stimulation scheme (C-Cont). S-Cont and C-Cont patterns were compared with conventional maximal stimulation (S-Max). Outcome measures include total work (W), end power (P), power fluctuation (PFI), charge accumulation (Q) and efficiency (η). Physiological measurements of muscle oxygenation (SmO) and heart rate were also collected with select participants.
At least one cadence-controlled stimulation pattern (S-Cont or C-Cont) improved P over S-Max in all participants and increased W in three participants. Both controlled patterns increased Q and η and reduced PFI compared with S-Max and prior open-loop studies. S-Cont stimulation also delayed declines in SmO2 and increased heart rate in one participant compared with S-Max.
Cadence-controlled selective stimulation improves cycling endurance and increases efficiency over conventional stimulation by incorporating fiber groups only as needed to maintain a desired exercise intensity. Closed-loop carousel stimulation also successfully reduces power fluctuations relative to previous open-loop efforts, which will enable neuroprosthesis recipients to better take advantage of duty cycle reducing patterns.
受激运动通常会受到激活肌肉快速疲劳的限制。减少激活纤维重叠和/或占空比的选择性神经刺激模式可以提高自行车运动的持续时间和强度。然而，独立激活纤维群体的不均匀输出可能会导致在每圈踏板旋转中产生功率和曲柄角度速度的巨大差异。通过刺激水平的反馈控制来强制保持恒定的步频可能会解决这个问题，并通过针对低于最大但高于稳态运动强度的目标来进一步提高耐力。
七名瘫痪患者使用标准节拍控制刺激（S-Cont）进行自行车运动。其中四人也使用低占空比（carousel）节拍控制刺激方案（C-Cont）进行自行车运动。将 S-Cont 和 C-Cont 模式与传统的最大刺激（S-Max）进行比较。测量指标包括总功（W）、终末功率（P）、功率波动（PFI）、电荷量（Q）和效率（η）。还选择了部分参与者进行肌肉氧合（SmO）和心率的生理测量。
至少有一种节拍控制刺激模式（S-Cont 或 C-Cont）提高了所有参与者的 P ，并使三名参与者的 W 增加。与 S-Max 和以前的开环研究相比，两种控制模式都增加了 Q 和 η，降低了 PFI。与 S-Max 相比，S-Cont 刺激还延迟了 SmO2 的下降并增加了一名参与者的心率。
节拍控制选择性刺激通过仅根据需要整合纤维群来维持所需的运动强度，从而提高了自行车运动的耐力并提高了效率。闭环 carousel 刺激还成功地降低了与以前的开环努力相比的功率波动，这将使神经假体接受者能够更好地利用占空比降低模式。
