Previous studies have shown that a single session of rehabilitation can evoke changes in motor control.1,2 Cirstea et al2 observed an improvement in performance in a single session of fast pointing movements in the upper extremity post-stroke, with a faster and more precise movement and fewer errors. In Chapter 3 during fast movement exercises of squats and steps, the movement pattern improved in a single session of squats which was demonstrated by an improved temporal coupling of the COP displacement and knee movements. There was only a tendency for the movement acceleration to increase in the paretic leg during the stepping exercises in Chapter 3 but improvements were observed in velocity of the paretic leg in Chapter 5 during the OKC exercises at the end of the OKC exercises in ankle dorsiflexion and knee flexion and extension. Although speculative, it is possible that removal of the postural demands imposed by the CKC exercise enabled the persons post-stroke to improve their movement velocity significantly in the open kinetic chain exercise.
The CKC and OKC exercises were both performed in a single session. An improved muscle activation pattern was observed in Chapter 3 in the CKC exercises of squats and steps and in Chapter 5 in the OKC single joint exercises, which was accompanied by increases in velocity and power of the OKC movements. Changes at the cortical level have been observed by Liepert et al1 with an increase in the cortical representation area of the paretic hand after a single session of physiotherapy. A single session of exercise that can modulate changes in EMG activity demonstrates the influence that exercise can have on the process of neuroplasticity. In a single session, the improvements cannot be attributed to natural recovery, which can be a confounding factor in the sub-acute phase.
In individuals post-stroke, Clark et al3 found that as the velocity of movement increased the paretic muscle activity did not increase. In Chapter 3, during the CKC exercises of
squats and steps, there was only a tendency for the velocity of the center of mass to increase by the end of the squats. Similarly during the steps, there was only a tendency for the peak knee acceleration amplitude to increase when the paretic leg was stepping, whereas the peak knee acceleration amplitude increased significantly in the non-paretic leg when stepping. These changes were accompanied by a significant increase in EMG area which demonstrates an ability of the paretic muscles to modulate increases in EMG area as the velocity or acceleration increases. In Chapter 5 during the OKC single joint exercises, the individuals post-stroke were able to modulate an increase in the EMG area as the peak velocity increased after practicing 50 single joint movements. Davies et al4 reported individuals were unable to generate a knee flexion movement with the paretic limb at velocities greater than 300ºs-1 and only three individuals could generate a knee extension movement. In Chapter 5, the individuals after stroke were able to generate an average velocity of ~330ºs-1 in the paretic leg at the start of the knee flexion exercises and this increased to ~365ºs-1 by the end of the knee flexion exercises. The knee flexion velocity in Chapter 5 was greater than those reported by Davies and colleagues4 and the difference may be related to the resistance torque. peak knee acceleration amplitude In our study, the torque was set at 0.5 Nm, whereas Davies and colleagues4 subjects were asked to generate the force as hard as possible. A lower resistance can promote a faster movement allowing for the modulation in EMG activity. Therefore, the amount of external resistance may be an important factor to consider when retraining speed of movement in stroke rehabilitation.
Age has been thought to be a limiting factor in recovery after a stroke, with younger individuals recovering at a faster rate and more completely. From the literature, there is evidence that older adults post-stroke have greater functional impairments when entering an inpatient rehabilitation facility, their scores on the Functional Independence Measure (FIM) or Barthel Index Score (BI) are lower.5-7 Upon discharge, the functional gains achieved are less than their younger counterparts,6 demonstrating that the rates of recovery post-stroke are greater for younger individuals than older.5,8 In Chapter 5, the participants were 15 years old than the stroke group in Chapter 3. In the older stroke group (Chapter 5), besides the stroke, there would be changes that occur in the muscle as the result of ageing such as reduced number of type II fast twitch fibers9 and reduced
number of motor units.10 The change in the muscle results in less force and power generating capacity of an ageing muscle.11 Depending on the level of mobility and functional capacity before the stroke, the stroke even if not as severe may have a greater influence on the functional level which may be the reason older individuals enter the inpatient rehabilitation facility with lower FIM and BI scores.5-7 The data in Chapter 5 revealed that the older stroke group showed significant improvements in the muscle activity, velocity and power in the OKC exercises in a single session which reflects the ability to recover or improve.