The EX group received a functional exercise program that included a combined strength and endurance training program for 8 weeks, whereas the CON group did not receive this exercise program. EX participants trained after school classes. The exercise training program consisted of functional strength and endurance training, which was designed by pediatric physical therapists as a group circuit. A functionally based exercise program was performed using simple equipment including leg stationary bicycles and elliptical machines (Figure 2). Prior to exercise, the participants had warm-up and cool-down periods with self-muscle stretching of the hip external rotator and abductor muscles, knee extensor and flexor muscles, and calf muscles. The total 70-minute exercise program consisted of a 5-minute warm-up period, 60 minutes of circuit exercises, and a 5-minute cool-down period. This 3 days per week training program was supervised by a physical therapist. Music was used to motivate participants. Both the EX and CON groups continued their physical therapy (PT) program for 1 session per week. A physical therapist from a special school determined the appropriate PT program for the participants. The PT program consisted of passive leg muscle stretching, upper limb activity in groups, sitting or standing ball throwing, handiwork, and a leisurely walk or playing for 1 hour during school hours. This physical therapist was also masked to each group. After school, the CON group had leisure time while we monitored their varied activities. They often had physical inactivity such as talking and playing with each other.
Functional strength training consisted of a sit-to-stand (STS) and a step up-down (SUD) activity. Each participant performed the standard protocols of the STS.19 For STS, each participant sat with hip flexion at 90°, knee flexion at 105°, ankle dorsiflexion at 15°, and feet flat on the floor. Most participants folded their arms over the chest, but participants who used assistive devices were permitted to use a stall bar. They were instructed to stand up at a comfortable speed without swinging their arms or moving their feet. Repetitions were counted each time their legs and hips were within 15° of the extended position. For SUD, participants stood in front of a step 17 cm in height for the starting position and moved up and down at a self-paced speed. During practice, the participants were allowed to hold the handrail if they felt unstable. Repetitions were counted when their legs returned to the starting position. In the first week of exercise training, the participants performed STS and SUD with free load for 8 to 10 repetitions per set, 3 to 5 sets per day, with 3 minutes' rest between sets. They were subsequently asked to wear a weighted vest. These weights were initially added in the second week as 30% of body weight, and afterward the progressive resistance was adjusted from 50% to 60% to 60% to 70% of 1-repetition maximum STS every 2 weeks.
Endurance training was performed on cycling and stepping machines in a circuit. The 3 stations for endurance training included (1) leg stationary bicycles, (2) elliptical machines, and (3) recreational fast walking or running. For leg cycling, participants initially sat on the saddle with a knee flexion of 30° to 35° and performed cycling with a self-selected speed and load. For the elliptical machine, the participants stood on the pedals, grabbed the handlebars, and pedaled their feet while pushing the handlebars alternately forward while stepping. For walking or running, each participant was asked to walk as fast as possible, or run in a race by picking up a ball from a basket and putting the ball in another basket placed 20 m away. Each participant continuously exercised on the leg stationary bicycles and elliptical machines for 15 minutes per session, and recreational fast walking or running was performed for 10 minutes, with a 5-minute rest between stations. Total exercise time was 40 minutes for the 3 exercise stations. Each participant was encouraged to perform the program to the end of the period. If the participants wanted to rest, they could stop. During the endurance exercises, the participants' heart rates were maintained at 65% to 85% of their maximum heart rate as determined with a heart rate monitor (FT4, Polar, Kempele, Finland). Maximum heart rate was defined as equal to 220 minus age of each participant.
Physical performance was evaluated using the 6-minute walk test (6MWT), 30-second sit-to-stand test (30sSTST), 10-m walk test (10mWT), Timed Up and Go test (TUGT), and a Functional Reach Test (FRT). All outcome measures have been shown to have high to very high levels of test-retest reliability.17–21 To determine the consistency of each measure, assessors evaluated the intratester reliability of variables. Outcomes were measured 1 week before the start of the program and within a week after the conclusion of the exercise program. All participants wore shoes and could use walking assistive devices during the tests if needed, and they were allowed to rest between testing for 3 to 10 minutes, or as required. All participants completed all outcomes.
6MWT is a measure used to assess functional cardiorespiratory capacity.16 The test-retest reliability is very high.20 A 40-m square course was replicated indoors. A 1-m wide walkway was designated with traffic cones and ropes between the 4 inside and outside corners of the course. Masking tape was placed at 2-m intervals along the route. The patients were instructed to walk as far as they could within 6 minutes. They were allowed to slow down or stop as necessary, and when they had to stop for rest, the duration of the rest period was recorded. The participants were given encouragement to do the test when examiners found that they did not try to walk continuously. The distance walked was recorded after the test.
30sSTST is a measurement of functional lower limb muscle strength and performance with a high test-retest reliability.21 30sSTST measured the number of repetitions for a sit-to-stand task within a 30-second period. Each participant sat on a chair without a backrest or armrest with feet flat on the ground, and hips and knees flexed at 90° and 105°, respectively. The examiner instructed the participant to repetitively move from the sitting to standing position as many times as they could within a 30-second period without using arms for support. Two participants who used walkers were allowed to use their support tool when their hips were extended at the end range. Repetitions of a sit-to-stand task were counted when their hips extended beyond 75°from sitting to standing.
10mWT is a measure to assess walking speed. 10mWT has a high test-retest reliability,21 and this test is correlated with gross motor functions for participants with CP.22,23 The test was conducted on a 14-m walkway that included 2 m at the start and end points to allow for acceleration and deceleration. Before the test, the examiner instructed, “Please walk towards the end, at your usual speed.” When the participant was given the cue “ready and go,” they walked toward the end of the walkway. The examiner started a timer when the participant's first foot crossed the plane of the 2-m line and stopped the timer when the first foot crossed the plane of the 12-m line. During the test, an examiner walked beside the participant and encouraged him/her to continue walking. The time to reach the middle of the 10-m walk was recorded for walking speed calculations.23,24
TUGT is a measure used to assess functional dynamic balance that has good test-retest reliability.24,25 Participants sat in an adjustable-height chair with no backrest or armrest. The height of the seat was adjusted such that both knee and hip flexion were 90° while sitting with the feet resting on the floor. None of participants wore shoes or orthoses, and participants with level III were allowed to use walking devices for the test. During the test, the participant stood up from an adjustable-height chair, walked a distance of 3 m, turned around a mark, walked back to the chair, and sat down again. Time was recorded from the “go” until the participant sat down in the chair. Each participant performed the test 3 times. The best time was recorded in seconds.25
FRT is a clinical measure of balance developed by Duncan et al26 that has excellent reliability.27 This study followed standard protocol.26 FRT measures the distance between the length of the arm and a maximal forward reach in the standing position. Participants were instructed to stand close to a wall (not wearing shoes or socks), but not touching the wall, with the dominant side arm position set at the zero mark of the stick, which was placed on a measuring stick against the wall at the height of the participants' acromion. The participants were asked to extend their arms to 90° of shoulder flexion. The assessor recorded the starting position at the third metacarpal head on the yardstick and instructed the participants to “reach as far as you can forward without taking a step.” The location of the third metacarpal was then recorded. The difference between the start and end positions was the reach distance. The test was repeated 3 times with 5-second rest intervals between each test, and the results were recorded and averaged for data analysis.
All data are presented as a mean (standard deviation). The distribution of the data was examined with the Shapiro-Wilk test for the assumption of normality. All data for 6MWT, 30sSTST, 10mWT, TUGT, and FRT were normally distributed. The difference between pre- and posttest for each outcome was analyzed with a paired t test. An analysis of covariance compared differences between adjusted posttest means between the 2 groups; the pretest means were used as covariates. The baseline differences of each outcome were analyzed using an independent t test. The individual training effect was further analyzed for the relationships of magnitude of change between 6MWT and other variables after the training using Pearson's correlation coefficient test. The power of the test was 0.8 and the level of significance was set at P < .05. The reliability of each tool was tested by 2 assessors using the test-retest intraclass correlation coefficient and Bland-Altman analyses.
Table 2 has the comparison outcomes within and between EX and CON. The intraclass correlation coefficients of the intrareliability of 6MWT, 30sSTST, 10mWT, TUGT, and FRT were 0.99, 0.97, 0.93, 0.99, and 0.75, respectively. The baseline scores of outcome variables were not significantly different between the groups. After the 8-week intervention, outcomes significantly improved in EX, except TUGT, but outcomes did not change in CON compared with the baseline scores. The adjusted postmean of EX and CON for each outcome was compared; the 6MWT, 30sSTST, 10mWT, and FRT in EX were significantly different in comparison with the CON means. TUGT was not significantly different between groups. Changes in 6MWT were positively correlated with 10mWT (r = 0.8, P < .001) but not with 30sSTST or FRT.
This study supported positive effects of a combined exercise training program on walking endurance (6MWT), walking speed (10mWT), leg muscle strength (30sSTST), and physical balance (FRT) for participants with CP. The task-specific exercise program designed to imitate functional mobility, such as sitting-to-standing with extra load, progressive step-up and step-down, walking and running, resulted in improved physical performance tests. Stationary cycling exercise improved respiratory and cardiovascular capacity and elliptical machine exercise reduced muscle tightness and increased range of motion of joints, which increases step length and speed and leg muscle strength and physical balance. The importance of muscle strength for participants with CP can be seen in the direct relation between strength and motor function. Participants with stronger knee extensors can walk faster.8 These results support previous research supporting improvement of muscle strength and physical fitness and HRQOL scores in participants with CP after exercise training.28,29
Our combined functional strength and endurance exercise program supported an increase in muscle strength associated with improvements of functional activities similar to the results of strength training alone.5,6,7–9 Despite the antagonism of concurrent training previously described in healthy people,30 it may be possible to integrate resistance and endurance training regimens for positive effects on physical performance.31,32 Increased muscle strength after the exercise training had a positive influence on activities of daily living in participants with CP. Many participants with CP experience difficulty when moving their bodies quickly or standing up from a chair. These disabilities are predictive of falls and subsequent disability. Increases in leg muscle strength support bodyweight during those movements.
Appropriate exercise and regular participation in activities are important goals for therapeutic interventions in participants with CP, and feasibility and reproducibility of the program are important factors in a clinical setting and after the school day. This study had 70-min/session durations and a frequencies of 3 sessions per week for 8 weeks, with a total of 3.5 hours per week of exercise. The exercise sessions were supervised by a physical therapist. Although the frequency, intensity, time, and type of exercise for health and fitness benefits in participants with CP are unknown, the design of an exercise training program could be based on the same principles as those for the general population. The findings of this study suggest that because a combined functional strength and endurance exercise program with supervision by a physical therapist elicits beneficial effects for physical functional ability in participants with CP, this program could be an alternative treatment in both clinical and school settings.
Our results did not show improvement in the TUGT because our exercise program did not include specific balance training. During the TUGT measurements, participants with CP had difficulty turning around while walking quickly because of limited balance or agility. Participants with CP have less ability to maintain their postural control during physical performance.25,29 Moreover, participants with spastic CP often have cocontractions of the distal and proximal muscles and do not have a smooth distal-to-proximal patterns of muscle activity.33
A limitation of the study was the lack of outcome measures across the World Health Organization International Classification of Functioning, Disability and Health. Because HRQOL is an important outcome of treatment for participant with CP, a long-term exercise training program is needed to maintain their fitness levels and HRQOL. Because it seems to be difficult for participants with CP to maintain their fitness level after an exercise program, future studies are needed to determine the clinical efficacy of a combined functional strength and endurance exercise program over the long term in participants with CP. Another limitation was the small sample of participants with CP. The study might be underpowered for some results, and thus a replication study with a larger sample is necessary before the results could be considered more than preliminary. Despite these limitations, our findings may contribute to the advancement of the general understanding of a combined functional strength and endurance exercise program for participants with CP.
This study provides evidence that an 8-week combined functional strength and endurance exercise program carried out as a group circuit can be an effective and feasible strategy for improving motor function, such as walking performance and leg muscle strength, in participants with CP. This study suggests that a concurrent lower body strength and endurance training program may provide positive adaptations in cardiorespiratory and motor function for physical activities of daily living and may lead to improvement of HRQOL in participants with CP.
The authors would like to thank all who participated in this study. The study was supported by the Research Center of the Back, Neck, Other Joint Pain and Human Performance, Faculty of Associated Medical Sciences, Khon Kaen University, Thailand. Additional thanks to Srisangwan, Khon Kaen Special School, for the location and equipment that was used in this study.
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Keywords:Copyright © 2017 Wolters Kluwer Health, Inc. and Section on Pediatrics of the American Physical Therapy Association. All rights reserved.
combined strength and endurance training; exercise training intervention; flexibility; leg strength; walking ability