Abstract This study compared one repetition maximum (1RM), muscle activity (EMG), and volume differences between rest-pause vs. traditional resistance training. Trained males (N = 20) were randomly assigned to either a rest-pause or a traditional training group. Pre and post 1RM testing was recorded. Training sessions were completed twice a week for 4-weeks and consisted of four sets of bench press to volitional fatigue at 80% of pretest 1RM with a 2-minute rest between sets. Total volume completed was recorded on each training day. Muscle activity of the pectoralis major was measured on the first and last training days. The RMS signals of the last repetition in the last set were normalized to the RMS peak values of the first repetition in the first set for each participant during the 1 st and 8 th training sessions. A 2-way repeated measures ANOVA indicated both groups significantly increased their 1RMs following the 4-week training protocol (p.05). An independent samples t-test indicated total volume lifted was significantly higher for the rest-pause group (56,778lbs vs. 38,315lbs; p <.05) throughout the protocol and independently during weeks 2, 3, and 4. While strength and muscle activity changes did not differ between groups, the rest-pause group achieved greater increases in volume than the traditional group. If volume is the focus of training (i.e., hypertrophy phases), the rest- pause resistance training method should be utilized. Methodology This mixed model repeated measures design study compared changes in strength, muscle activity, and lifting volume between four weeks of rest-pause and traditional resistance training. The independent variable in this study was resistance training type (i.e. rest-pause and traditional), and the dependent variables included changes in 1RM bench press, total lifting volume, and peak pectoralis major muscle activity. Work was used as the measure of lifting volume and was calculated by multiplying the number of repetitions completed multiplied by the mass of the load bar (80% 1RM). At the start of the first and eighth training sessions, surface electrodes were placed on the skin over pectoralis major of the dominant hand side. This location is at the most superior part of the pectoralis major on the medial sternum lateral to the supra sternal notch (Keogh et al., 1999). Electrode placement was placed one third of the distance from the super sternal notch and the anterior axillary line. The EMG signals during all lifts were band-pass filtered with cut-off frequencies of Hz. The signals were then full-wave rectified and smoothed using a root-mean-square (RMS) filter with a moving window of 250 ms. During the 1 st and 8 th training session, the RMS signals during the last repetition of the last set were normalized to the RMS peak values during the first repetition of the first set for each participant (i.e. percent change from peak first repetition). The total lift included both eccentric and concentric phases. Statistical Analysis Separate 2 (groups: traditional and rest-pause) x 2 (time; before and after 4-weeks of training) analysis of variance (ANOVA) for repeated measures was used to assess the differences in 1RM and muscle activity in the dominate pectoralis major between rest-pause vs. traditional training groups. Independent samples t-tests were used to assess total volume changes over the 4-week training protocol and to compare volume differences between the two groups for each of the 4-weeks. Introduction Several training strategies including heavy weight, eccentric action, slow-motion, breakdowns, and maximal power training, have been used in an effort to produce maximal gains (Keogh et al., 1999). The rest-pause method incorporates a prolonged pause between individual repetitions within a set (Krol et al., 2007). Keogh et al. utilized a two second rest period between each repetition for the rest-pause lifting protocol while Marshall et al. set the rest period at 20-seconds after completing a 20-repetition maximum (RM) for the squat exercise (Keogh et al., 1999, Marshall et al., 2012). Hypertrophy phases promote completing sets to volitional fatigue often comprising of 6-12 repetitions. The adenosine triphosphate (ATP) - phosphocreatine (ATP-PCr) system can sustain muscle energy requirements for approximately 10-seconds during high intensity exercise bouts (McArdle et al., 2014). Rest periods have been extensively examined and Miranda et al. concluded that rest periods of three minutes appear to have much more significant increase in volume lifted in comparison to one minute rest periods (Miranda et al., 2007). The purpose of this study was to compare changes in 1RM bench press, lifting volume, and peak pectoralis major muscle activity after 4-weeks of either rest-pause or traditional resistance training. It is hypothesized that the rest-pause training group will have a greater increase in 1RM bench press, complete more lifting volume, and have a greater change in pectoralis major muscle activity than the traditional training group. Results Effect of Rest-Pause vs. Traditional Bench Press Training on Muscle Strength, Electromyography, and Lifting Volume JA Korak a MS CSCS, MR Paquette b PhD, J Brooks b, DK Fuller a PhD, JM Coons a PhD Middle Tennessee State University, Murfreesboro, TN a University of Memphis, Memphis, TN b Training Protocol Week SessionsRest-Pause**Traditional 11 RM Max (pre)1 RM Max (pre) Week 1 24sets to fatigue* 4sets to fatigue* 80% 1 RM (2 mins rest) 34sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) Week 2 44sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) 54sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) Week 3 64sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) 74sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) Week 4 84sets to fatigue 4sets to fatigue 80% 1 RM (2 mins rest) 94sets to fatigue (EMG)* 4sets to fatigue* 80% 1 RM (2 mins rest) 101 RM Max (post)1 RM Max (post ) Notes: * indicates EMG recorded during first and fourth set ** indicates a 4 second pause between repetitions Descriptive Statistics for 1RM and Muscle Activity Variable Rest-PauseTraditional 1RM (lbs.) Pre-Training (58.4) (49.7) Post-Training * (58.4) (47.8) Peak EMG (%) Pre-Training 32.1 (54.6) 44.2 (50.0) Post-Training 19.9 (34.1) 53.8 (54.9) Notes. * : indicates p <.05 for Post-training vs Pre-training 1RM scores. EMG: electromyography. EMG data represent the percent change in RMS signal from the 1 st and 4 th sets during the 1 st (Pre-Training) to the 8 th (Post-Training) sessions for both groups. Data are presented as M and SD Descriptive Statistics for Study Participants ­­­­­­­­­­­­­­­­­ Group Ht. (cm) Wt. (kg) Age (yrs) 80% TL (lbs) Rest-Pause (n =10) (5.2) 81.5 (8.5) 23.0 (2.0) (46.3) Traditional (n = 10) (4.6) 77.8 (10.4) 23.1 (2.6) (38.7) Note. TL = Training load Data are presented as M and SD Key Findings Both groups significantly increased their 1RM from pretest to posttest, F(1,18) = 37.45, MSE = 98.96, p <.001, ɳ 2 p =.68. Total volume lifted was significantly higher for the rest-pause group (M = 56,778lbs, SD = 23,522lbs, n = 10) in comparison to the traditional training group (M = 38,315lbs, SD = 7,870lbs, n = 10), t (18) = 2.35, p =.030. The rest-pause group had significantly higher volume during weeks two (t = 2.66, p =.016), three (t = 2.75, p =.013), and four (t = 2.58, p =.019) in comparison to the traditional training group. Descriptive Statistics for Volume (lbs) Totals Variable Rest-Pause Traditional Week 1 volume 12,684.7 (8,088.8) 9,012.7 (2,705.4) Week 2 volume 13,296.4 (4,861.5)* 8,933.9 (1,819.1) Week 3 volume 15,158.3 (5,987.8)* 9,640.1 (2,124.2) Week 4 volume 15,638.6 (5,562.5)* 10,729.0 (2,274.7) Total volume 56,778.0 (23,522.4)*38,315.0 (7,870.0) Note. *indicates p <.05 between rest-pause vs. traditional training group Data are presented as M and SD References Keogh, JWL, Wilson, GJ, Weatherby, RP. A cross-sectional comparison of different resistance training techniques in the bench press. J Strength Cond Res 13(3): , Krol, H, Sobota, G, Nawrat, A. Effect of electrode position on emg recording in pectoralis major. J Hum Kinetics 17: , Marshall, PWM, Robbins, DA, Wrightson, AW, Siegler, JC. Acute neuromuscular and fatigue responses to the rest-pause method. J Sci Med Sport 15: , McArdle, WD, Katch, FI, Katch, VL. Exercise Physiology, Nutrition, Energy, and Human Performance 8 th Edition. Baltimore, MD: Lippincott Williams and Wilkins, Miranda, H, Fleck, SJ, Simao, R, Barreto, AN, Dantas, EHM, Novaes, J. Effect of two different rest period lengths on the number of repetitions performed during resistance training. J Strength Cond Res 21(4): , 2007.