Author(s): JOHNSTON, H., FERGUSON, R. TOLFREY, V., Institution: UNIVERSITY OF BIRMINGHAM, Country: UNITED KINGDOM, Abstract-ID: 1020

INTRODUCTION:
Athletes with cerebral palsy (CP) exhibit reduced capacity to generate power [1], primarily due to impairments in voluntary activation, motor unit recruitment and firing rate, excessive co-contraction, and muscle weakness [2]. Muscle temperature (Tm) strongly influences neuromuscular function and performance in non-disabled (ND) individuals by altering muscle power generating characteristics, nerve conduction velocity and muscle coordination [3]. However, the effect of Tm in athletes with CP remains unexplored. This study investigated the effects of passive Tm manipulation on maximal sprint power and neuromuscular activity in athletes with CP compared to ND athletes.
METHODS:
Nine athletes with CP and nine sex and sport-matched ND athletes (ND) performed a maximal 30-s sprint on a cycle ergometer under three Tm conditions; HOT (40.0 ± 0.3oC water immersion), NEUTRAL (21.7 ± 0.9oC passive rest) and COLD (10.9 ± 0.7oC water immersion). Tympanic (Ttymp) and skin (Tsk) temperature were measured throughout. Tm was measured following temperature manipulation in a separate ND subgroup (n=4). Bilateral power output (peak [PPO], mean [MPO], limb asymmetry) and surface EMG of the vastus lateralis (VL) and biceps femoris (BF) were collected throughout the maximal sprint. Data were analysed using ANOVA with Bonferroni post-hoc comparisons, with significance set at p≤0.05. Data are reported as mean ± SD.
RESULTS:
Tsk decreased from HOT to NEUTRAL to COLD (p<0.001) comparably between groups. Manipulation of Tm was confirmed (COLD 32.4 ± 1.1oC, NEUTRAL 36.3 ± 0.2oC, HOT 38.1 ± 0.1oC). Across conditions, athletes with CP produced lower power output than ND and exhibited greater inter-limb asymmetry (18.5 ± 12.3% vs. 3.8 ± 4.1%, respectively). In CP, PPO was lower in COLD (409 ± 147 W) than HOT (496 ± 182 W) with no differences compared to NEUTRAL (478 ± 187 W). MPO was lower in COLD (313 ± 109 W) than HOT (373 ± 133 W) and NEUTRAL (352 ± 131 W). In ND, PPO was lower in COLD (746 ± 171 W) than HOT (999 ± 199 W) and NEUTRAL (979 ± 239 W). MPO was lower in COLD (562 ± 120 W) than HOT (701 ± 143 W) and NEUTRAL (679 ± 148 W). There was no difference between NEUTRAL and HOT in either group. Normalised EMG amplitude increased as Tm decreased from HOT to NEUTRAL to COLD in CP (p=0.044). In ND, normalised EMG amplitude increased relative to HOT, not from NEUTRAL to COLD. EMG co-activation of the VL and BF was higher in CP than ND throughout (66.8 ± 13.6% vs. 42.6 ± 11.4%, respectively; p<0.001).
CONCLUSION:
In athletes with CP, muscle temperature manipulation induced smaller performance changes than in ND athletes (17.6 vs. 25.4%, respectively), but greater changes in EMG amplitude, particularly at higher power outputs and colder temperatures. Minimising reductions in Tm remains important for athletes with CP.

[1] Runciman et al (2015). Am J Phys Med Rehabil. 94(1):28-37
[2] Rose and McGill (2005). Dev Med Child Neurol. 47(5):329-36
[3] Racinais et al (2017). Temperature. 4(3):227-257