Comparison between pre-exhaustion and traditional exercise order on muscle activation and performance in trained men.

Author:Soares, Enrico Gori
Position:Research Article - Report
 
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Introduction

Optimal prescription of resistance training programs relies on proper organization of training variables, such as frequency, intensity, volume, rest intervals, velocity, choice and order of exercise, and periodization (Baker et al., 2010; Foster et al., 2001). Previous research has demonstrated the importance of varying exercises and volume load (repetitions x intensity) during a resistance training program designed to increase muscle cross-sectional area and maximum strength (Fonseca et al., 2014).

The exercise (multi-joint vs single-joint exercises) significantly affects several acute training responses, such as maximal number of repetitions, neuromuscular activity (sEMG), neuromuscular fatigue, oxygen consumption, and rating of perceived exertion (RPE) (Simao et al., 2012). Multiple-joint exercises, such as bench press and back squat, require more complex neural responses, considering the high number of active muscles. In contrast, single-joint exercises, such as triceps pushdowns, have been used by those with low technical skills to target specific muscle groups (Ratamess et al., 2009). Although, there are several different ways to organize the exercise order in a resistance training program, many of them are related to sequencing of single- and multiple-joint exercises (Ratamess et al., 2009). The scientific literature has focused on primarily two different exercise order sequences, which may be classified as either whole-body or specific muscle (Simao et al., 2012; Soares and Marchetti, 2013). A whole-body exercise order is comprised of several multi- and single-joint exercises sequentially (Belleza et al., 2009; Chaves et al., 2013; Monteiro et al., 2005; Romano et al., 2013; Silva et al., 2009; Simao et al., 2007; Spreuwenberg et al., 2006), while a specific exercise order involves performing one exercise after another for the same mucle group, such as a traditional sequence (TR) (Ratamess et al., 2009) or pre-exhaustion (PE) sequence (Augustsson et al., 2003; Brennecke et al., 2009; Gentil et al., 2007). The PE sequence involves working the same muscle or muscle group to the point of neuromuscular failure using a single-joint exercise immediately followed by a related multi-joint exercise while the TR sequence uses the reverse order (multi-joint prior to single-joint) (Augustsson et al., 2003; Brennecke et al., 2009; Gentil et al., 2007). The rationale for a PE sequence lies in increased motor unit recruitment during neuromuscular fatigue, resulting in greater muscle activation for subsequent multi-joint exercises. However, Gentil et al. (2007) investigated the effects of a PE sequence on upper-body muscle activation during bench press exercise and reported that performing a pec deck exercise immediately prior to a bench press led to similar sEMG amplitude of both the anterior deltoid and pectoralis major muscles. These results further demonstrated that the total number of repetitions were not significantly different between sequences; however, it was observed that there was an increase in triceps brachii activation and a performance decrement during the bench press exercise with a PE sequence. Despite this performance impairment, an increase in sEMG during the PE sequence may occur due to neuromuscular fatigue of some muscles which is compensated for by increased motor unit recruitment of other muscles in an attempt to maintain performance. Additionally, Brennecke et al. (2009) analysed the pectoralis major, triceps brachii and anterior deltoid activation in the bench press alone and in a PE sequence (pec deck fly and bench press) in trained men. The results reported by Brennecke et al. (2009) were similar to Gentil et al. (2007) in that the PE sequence did not increase muscle activation of either the pectoralis major or anterior deltoid muscles, but did increase sEMG in the triceps brachii.

Despite the existing literature that has examined volume load and sEMG characteristics of a PE exercise sequence, no previous research has compared these characteristics or others with a TR exercise sequence or muscle order. Therefore, the purpose of this study was to combine an analysis of load, maximal repetitions, metabolic characteristics, and sEMG in order to understand the varied aspects of exercise order. Therefore, the purpose of this study was to measure the acute effects of PE vs. TR exercise order on neuromuscular performance and sEMG in trained men.

Methods

Subjects

Based on a statistical power analysis derived from iEMG data from a pilot study, a sample size of ten subjects would be necessary to achieve an alpha level of 0.05 and a power (1-P) of 0.80 (Eng, 2003). Therefore, 14 young, healthy, resistance trained men (age: 25.5 [+ or -] 4.0 years, height: 1.75 [+ or -] 0.04 m, and total body mass: 80.0 [+ or -] 11.1 kg, biacromial width: 37.1 [+ or -] 2 cm; 10 RM bench press: 680.4 [+ or -] 170 N and 10RM triceps pushdown: 260.6 [+ or -] 80.1 N) were recruited to participate in the current study. The subjects had at least one year of experience with the bench press and triceps pushdown exercises with no previous surgery or history of injury with residual symptoms (pain) in the upper limbs within the last year. This study was approved by the University research ethics committee and all subjects read and signed an approved informed consent document.

Experimental procedures

All subjects were right-arm dominant based on their preferred arm to write. Subjects were instructed not to perform any resistance exercises for 48 hours before testing. All tests were randomized and counterbalanced for all subjects and experimental conditions. Volunteers attended one session in the laboratory which was separated into two parts. First, each subject was instructed in the proper technique and rate for each exercise as follows: (a) bench press--Subjects lay supine on a weight-lifting bench and grasped a barbell with the elbows fully extended, then the barbell was lowered vertically (eccentric phase) to touch the chest then returned to a fully extended elbow position (concentric phase) at the start position; and (b) triceps pushdown--push down with the hands by extending the elbows until they were fully extended (concentric phase) then returned to the start position (eccentric phase). All subjects performed ten repetition maximum (10RM) tests for each exercise (bench press and triceps pushdown) to determine the maximum weight that could be lifted for 10 consecutive repetitions at a constant rate of four seconds per repetition (two seconds concentric and two seconds eccentric). If they did not accomplish 10RM in the first attempt, the weight was adjusted by 4-10 kg and a minimum five minute rest was given before the next attempt. Only three trials were allowed per testing session in order to avoid neuromuscular fatigue. Subjects received standard instructions regarding technique, and exercise execution was monitored and corrected when necessary, ensuring no stopping between eccentric and concentric phases for each test. For a successful...

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