Position-Dependent, Hyperexcitable Patellar Reflex Dynamics in Chronic Stroke  Chung-Yong Yang, MD, PhD, Xin Guo, PhD, Yupeng Ren, MS, Sang Hoon Kang, PhD, Li-Qun Zhang, PhD  Archives of Physical Medicine and Rehabilitation  Volume 94, Issue 2, Pages 391-400 (February 2013) DOI: 10.1016/j.apmr.2012.09.029 Copyright © 2013 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 1 Experimental setup for instrumented patellar tendon reflex test. A subject sat on an adjustable seat. The trunk, thigh, leg, and foot were strapped to the backrest, seat, leg-supporting frame, and footplate, respectively. The knee joint was aligned to the torque sensor, which was connected to a locked servomotor. A dome-shaped rubber pad was attached to the patellar tendon at the location with the strongest reflex response. The tendon hammer with a force sensor mounted at its head was used to tap the patellar tendon through the rubber pad. EMG electrodes were attached on quadriceps muscle surface. Abbreviations: DSP, digital signal processor; PC, personal computer. Archives of Physical Medicine and Rehabilitation 2013 94, 391-400DOI: (10.1016/j.apmr.2012.09.029) Copyright © 2013 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 2 Representative tendon tapping results and impulse responses over multiple taps of the patellar tendon with the knee joint at 60° of flexion in a control subject (A1–A4) and a stroke survivor (B1–B4). Solid line and dashed lines on plots (A1–A3 and B1–B3) represent mean and SD, respectively. In the impulse responses plots (A4 and B4), vertical lines represent (1) onset of tapping impact, (2) onset of reflex-mediated torque response, (3) peak torque response, and (4) point at which the torque drops to 50% of its peak value. Archives of Physical Medicine and Rehabilitation 2013 94, 391-400DOI: (10.1016/j.apmr.2012.09.029) Copyright © 2013 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 3 Comparison of neuromechanical data, including Gs (A), Rc (B), Rhr (C), td (D), fth (E), Mp (F), and EMGp (G) between the control and stroke groups at each knee flexion angle and across the 6 knee flexion angles. The P value over vertical columns indicates mean difference between the stroke and control groups at each knee angle, while transverse lines represent trend lines across each knee angle of subjects. The error bars on the vertical columns represent SEM. ∗P<.05, †P<.10 by Student t test between 2 groups. Archives of Physical Medicine and Rehabilitation 2013 94, 391-400DOI: (10.1016/j.apmr.2012.09.029) Copyright © 2013 American Congress of Rehabilitation Medicine Terms and Conditions

Fig 4 The distribution of Pearson correlation coefficients derived from significantly correlated values between neuromechanical data (Gs, Rc, Rhr, and Mp) and 2 clinical measurements (DTR and MAS) across the different flexion angles. The dotted line box represents the knee joint angle area of the relatively higher correlation coefficients, spanning 60° to 75° of knee flexion. Archives of Physical Medicine and Rehabilitation 2013 94, 391-400DOI: (10.1016/j.apmr.2012.09.029) Copyright © 2013 American Congress of Rehabilitation Medicine Terms and Conditions