1. The Differences of Rectus Abdominis Muscle Activation between Volleyball and Hockey Player while Performing Abdominal Crunches Asha Hasnimy Mohd Hashim, Mohd Shafie Abdul Rahman, Halijah Ibrahim and Zainal Abidin Zainuddin Faculty of Education Universiti Teknologi Malaysia Graph 1: Mean value (mV) of rectus abdominis sub-unit contraction between hockey and volleyball players Right 1Right 2Right 3Right 4Left 1Left 2Left 3Left 4 Hockey 0.11080.12860.19230.15190.10110.09630.24810.1944 Volleyball 0.20580.21440.19340.15520.25510.22780.18600.1260 Introduction Abdominal crunches is widely known as one method of exercise to strengthen rectus abdominus muscle. However, the effectiveness of this exercise to strengthen all sub- unit of rectus abdominis muscle has been questioned. It is reported that, only a part of rectus abdominis been activated while performing abdominal crunches. This may due to the nature of sports which require different sub-unit of rectus abdominis to activate although performing the same task. Therefore, a research has been conducted to identify and analyse the rectus abdominis sub-unit activation while performing abdominal crunches between a volleyball and a hockey player. Method Subjects: Chosen from university’s volleyball and hockey team. Procedure: Subjects are required to perform abdominal crunches (lie on back with knee bend, lift shoulders off the floor, concentrating on moving ribs towards hips. Hands on chest. Go slow and keep breathing - 2 seconds up, hold for 2 seconds, then 2 seconds going down.). While performing abdominal crunches, subjects are required to wear electrode on their rectus abdominis (divided into 8 sub-unit). The rectus abdominis sub- unit activation were recorded using Biopac Student Lab: (Electromyography) software and was analysed using Statistical Packages for Social Science version 14.0 (SPSS 14.0). Table 1: Mean value (mV) of rectus abdominis sub-unit contraction between hockey and volleyball players Results The mean value (mV) of rectus abdominis sub-unit contraction between hockey and volleyball players is shown in Table 1 and been translated in graph 1 for comparison. In general, there are large differences in mean values of rectus abdominis sub-unit contraction between hockey and volleyball players except in sub-unit right 3 and right 4. Figure 1: Illustration on performing abdominal crunches References Basmajian, J.V. and Deluca, C.J. (1985). Muscles Alive: Their Functions Revealed by Electromyography. Williams & Wilkins: Baltimore. Furlani J. and Bankoff A.D. (1987) Electromyographic analysis of the rectus abdominis and external oblique muscles during exercises in lateral decubence. sitting and kneeling positions. Electromyography Clinical Neurophysiology, 7(27), 265-272. Piering, A.W., Janowski, A.P., Moore,M.T, Snyder,A.C. and Wehrenberg, W.B. (1993). Electromyographic analysis of four popular abdominal exercises. Journal of Athletic Training, 28 (2), 120-126. Sternlicht E., Rugg, S.G., Bernstein, M.D. and Armstrong, S.D. (2005). Electromyographical analysis and comparison of selected abdominal training devices with a traditional crunch. Journal of strength and conditioning research, 19(1), 157–162 Figure 2: EMG wave during muscle contraction Figure 2: Subunit of muscle activitation However, T-test analysis shows that there are significant differences in all rectus abdominis sub-unit activation while performing abdominal crunches (right1, t= - 179.507, p=0.000; right 2, t= -110.299, p=0.000; right 4, t= -3.058, p=0.007; left 1, t= -181.037; p=0.000; left 2, t= -162.662, p=0.000; left 3, t= -48.997, p= 0.000 and left 4, t= -75.264, p= 0.000) between hockey and volleyball player except for sub-unit right 3, t= -1.199; p=0.246. Regardless to the type of sports, it is shown that the right side of rectus abdominis is less activated compared to left side, where left 1 and left 3 are more activated when compared to the other two (right 1 – left 1, t= -2.918, p =0.009; right 2 – left 2, t=1.799, p=0.088; right 3 – left 3, t= -3.319, p=0.004 and right 4 – left 4, t= -0.809, p= 0.429). Discussion Other researchers have noted differences in muscle activity between the upper and lower halves of the rectus abdominis while performing specific abdominal exercises (Basmajian & Deluca, 1985). This is attributed to the fact that the other studies divided the muscle in half and compared the electrical activity between the upper and lower halves while we divided the muscle into its anatomical units and compared the electrical activity across quadrants. The present study found that right and left side of rectus abdominis are activated differently and it contradicts the findings Furlani & Bankoff (1987) and Piering et. al. (1993). This may due to the nature of sports or human habit that tends to activate only one side of body or certain unit of muscles compared to the other. For example, a hockey player tends to flex their trunk on the right side of body meanwhile for volleyball player repetitive trunk flexion and extension is the nature of the game. Thus it shown that abdominal crunches exercise alone will not activate all sub-unit of the rectus abdominis and therefore, other abdominal exercises are needed to activate other rectus abdominis sub-unit.