396 B-38 Free Communication/Poster - Resistance Exercise JUNE 1, 2011 1:00 PM - 6:00 PM ROOM: Hall B 1692 Board #225 June 1 3:30 PM - 5:00 PM Core Exercises That Incorporate Distal Trunk Muscles Maximize Primary Trunk Muscle Activation Jinger S. Gottschall 1 , Jackie Mills 2 , Bryce Hastings 2 . 1 The Pennsylvania State University, University Park, PA. 2 Les Mills International, Auckland City, New Zealand. (Sponsor: W. Larry Kenney, FACSM) Email: jsg2 0 @psu.edu (J.S. Gottschall: Contracted Research; Les Mills International.) The American College of Sports Medicine and the United States Department of Health and Human Services recommend that healthy adults, under 65 years of age, complete a strength training routine that includes core exercises twice a week. They specifically advocate core training as a means to improve stability, reduce injury, and maintain mobility. There are countless exercises that target the primary core trunk muscles (abdominal and lumbar) with the aim of providing these benefits. However, it is unknown which exercises elicit the greatest activation thereby maximizing strength and functional gains. PURPOSE: To determine whether core exercises that require activation of the distal trunk muscles (deltoid and gluteal) elicit greater activation of primary trunk muscles in comparison to core exercises that only require activation of the primary trunk muscles. METHODS: Fourteen participants, 7 men and 7 women, completed 16 randomly assigned exercises (for example, traditional trunk flexion, upper locust trunk extension, unilateral standing balance, and forearm plank variations). Each exercise was performed for 10 repetitions at a cadence of 15 repetitions per minute with the exception of the balance poses, which were performed statically for 20 seconds. Therefore, all the exercises were analyzed during a 20 second period. We measured surface electromyography of the anterior deltoid, rectus abdominus, external abdominal oblique, lumbar erector spinae, and gluteus maximus. In order to determine if the muscle activation differed between exercises, we normalized the active muscle periods, performed a repeated-measures ANOVA and defined the statistical significance at p < 0.05. RESULTS: Activation of the abdominal and lumbar muscles was greatest during the exercises that required activation of deltoid and gluteal muscles. For instance, the forearm plank variations required over two times the average activity of the rectus abdominus, external abdominal oblique, and lumbar erector spinae compared to a traditional trunk flexion and extension exercise (p = 0.02). CONCLUSIONS: When completing the core strength guidelines, a routine that incorporates the activation of distal trunk musculature would be optimal in terms of maximizing strength, improving stability, reducing injury, and maintaining mobility. 1693 Board #226 June 1 3:30 PM - 5:00 PM A Reexamination Of The Efficiency Of Electrical Activity Technique (EEA) For Identifying The Neural Versus Hypertrophic Contributions In The Time Course Of Strength Gains Jason M. DeFreitas, Travis W. Beck, Matt S. Stock, Paul R. Kasishke II. University of Oklahoma, Norman, OK. Email: defreitas@ou.edu (No relationships reported) The strength gains that occur during resistance training are due to two primary adaptations: neural factors and hypertrophy. Neural factors are believed to be the primary contributor to strength gains during the first 4-6 weeks of training with hypertrophy becoming increasingly important in subsequent weeks. Tracking changes in the EMG vs. force relationship can be used for estimation of the % contributions of these adaptations. This model assumes that hypertrophy leads to increased efficiency of electrical activity (EEA). PURPOSE: To establish a more precise time course of these adaptations by performing weekly testing. METHODS: Thirteen untrained men completed 8 wks of training (3 days/wk). Isometric strength and EMG amplitude of the leg extensors were measured each week. RESULTS: The training led to increases in EMG (20%), and strength (14.3%). However, the slopes of the EMG vs. force relationship did not decrease with training, thereby indicating no change in EEA. Due to unexpected variability in the slopes, the model for calculating the % contributions provided inconsistent results. As shown in the table, the mean % contributions to strength gains of neural factors (NF) and hypertrophy (H) were highly variable and often impractical. The nature of the model forces the sum of the adaptations to always be 100%, but the existence of percents higher than 100 combined with negative values has no practical application. CONCLUSION: The EEA model was unsuccessful in the present study in estimating a more precise time course of the neural and hypertrophic contributions to strength gains. The effect of resistance training on the slopes was highly variable and resulted in % contributions that were impractical. Table 1 Wk 1 Wk 2 Wk 3 Wk 4 Wk 5 Wk 6 Wk 7 Wk 8 %NF 230 65 100 102 17 488 -669 79 Mean %H -130 35 0 -2 83 -388 769 21 1694 Board #227 June 1 3:30 PM - 5:00 PM Muscle Recovery After a Session of Resistance Training Monitored Through Serum Creatine Kinase Jeferson M. Vianna 1 , Antonio Castro 1 , Patricia Panza 2 , Dihogo G. Matos 2 , Mauro M. Filho 2 , Vinicius O. Damasceno 3 . 1 Federal University de Juiz de Fora, Juiz de Fora, Brazil. 2 University de Trás os Montes e Alto Douro, Vila Real, Portugal. 3 University Salgado Filho, Juiz de Fora, Brazil. Email: jvianna@acessa.com (No relationships reported) Recovery is described as a multifactorial process by which the body tries to overcome the effects of fatigue induced by training. Several biochemical markers of muscle damage have been used in order to monitor recovery, among which is creatine kinase (CK). PURPOSE: The objective was to monitor serum CK during the recovery period after a session of resistance training. Copyright © 2011 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.