INTRODUCTION: Cerebral Palsy (CP) is the most common disabling motor disorder found during childhood, occurring in 2.1-3.2 of every 1,000 births. Motor functionality of children with CP is commonly compromised and is classified with a gross motor function classification score (GMFCS) and with the gross motor function measure (GMFM). Balance ability has typically been assessed using single leg stance test (SLST) time but more recently, center of pressure excursion (COPE) has shown to be a more valid measurement in populations with altered motor abilities. However, COPE has not been used to test balance in the CP population, yet. This study aimed to determine if relationships were present between COPE measurements, functionality measurement scores (GMCS and GMFM) and reported fall frequency. It was hypothesized that i) larger COPE measurements would be associated with a higher GMFCS level and lower GMFM score, and that ii) COPE measurements would be significantly higher in children with a high reported incidence of fall frequency. METHODS: Gross functionality was measured using a GMFM score and GMFCS level. Balance ability was assessed using COPE measurements on a force plate and SLST time. Fall frequency was determined by a short questionnaire. A Pearson correlation analyzed COPE measurements vs. mean GMFM score. A one-way ANOVA was used to compare COPE measures between GMFMCS levels, with a Bonferroni post-hoc test. Lastly, an independent sample t-test analyzed differences in COPE measurements and SLST time between fall frequency groups. RESULTS: Significantly larger COPE velocities were demonstrated in children who reported a greater number of falls in the past month and were considered high risk for falling (p = 0.02). No relationships were demonstrated between COPE measurements and GMFM score. GMFCS level III participants demonstrated statistically significant lower COPE velocity compared to GMFCS level II participants (p = 0.05). There were no significant differences in SLST between high and low risk fall groups (p = 0.07). DISCUSSION: Children with higher reported fall frequencies demonstrated a 60% increase in COPE velocity, compared to those with little to no falls. Clinical GMFM scores did not demonstrate significant correlations to COPE measurements and may not be an appropriate identifier for falling in children diagnosed with CP. This is the first trial to evaluate COPE measurements and reported fall frequencies in children diagnosed with CP. The use of a force plate to determine COPE velocity during a SLST is useful in identifying children with CP who may be at an elevated risk for experiencing a fall. COPE velocity was able to provide intricate quantitative data regarding fall risk that could not be obtained during a normal SLST.

INTRODUCTION: Cerebral Palsy (CP) is a sensorimotor disorder characterized by dysfunctional motor coordination, balance problems, and loss of selective motor control. Motor coordination exhibited as co-contraction, has been subjectively quantified using gait analysis, but recent studies have begun to objectively analyze the amount of co-contraction by collecting electromyography (EMG) data. Center of pressure excursion (COPE) measurements collected during a single leg standing test (SLST) have shown to be more valid measurements of balance in populations with motor disabilities than a SLST alone. A recent study has correlated increased COPE velocity with a lower fall risk as determined by reported fall frequency, suggesting a more objective measure of fall risk. The current study aimed to determine if the fall risk calculated by COPE velocity in children with CP is correlated with co-contraction index value in various muscle synergy groups. It was hypothesized that i) co-contraction index values will differ between high and low fall risk groups, ii) there will be preferential activation of different synergy groups within the high and low fall risk groups, and iii) there will be a negative and direct correlation between COPE velocity and co-contraction index values for all synergy groups. METHODS: Fall risk grouping was determined by average COPE velocity values calculated from previously reported fall frequency groups. Balance ability was determined by COPE measurements during a SLST on a force plate. Muscle synergy groups were determined by common muscle pairings at the hip, knee and ankle. Co-contraction indices were determined from linear envelopes plotted from muscle group EMG data. An independent t-test was run on muscle synergy groups between high and low fall risk groups. Nonparametric Analysis of Variance (ANOVA) and Tukey post-hoc tests were run on the high and low fall risk groups separately to determine differences in co-contraction index value within high and low fall risk groups. A Pearson correlation analyzed COPE velocity and co-contraction index value. RESULTS: No significant differences in muscle synergy between the high and low fall risk groups were found (p = 0.476, 0.076, 0.064, 0.364). The ANOVA and Tukey post-hoc tests for high fall risk group found significant differences in co-activation index value between the sagittal hip and frontal hip groups (p = 0.022) and sagittal hip and ankle groups (p = 0.016). Low fall risk group was found to have significant differences between the sagittal hip and frontal hip groups (p = 0.038) and frontal hip and knee groups (p = 0.012). Weak and negative correlations were found between COPE velocity and both knee and ankle groups (r = -0.309, -0.323, p = 0.059, 0.050). Negligible and insignificant correlations were found between frontal hip and sagittal hip synergies and COPE velocity ((r = 0.013, -0.068, p = 0.475, 0.367). CONCLUSION: There is insufficient evidence to claim that muscle group activations are different depending on fall risk grouped by COPE velocity. It is not currently possible to correlate COPE velocity to a specific synergy group recruitment. However, data do suggest that sagittal hip and knee strategies are recruited more than ankle and frontal hip strategies during SLST.