Rest Intervals during Resistance Training Affect the Rating-Perceived Exertion and Muscle Performance in Untrained Subjects

IntroductionMultiple-set resistance training promotes higher improvements in strength and hypertrophy as compared with single set (Krieger, 2010; Rhea et al., 2002). Therefore, training volume is an important variable related to these neuromuscular adaptations (American College of Sports, 2009). During a resistance exercise (RE) session the number of repetitions performed by a subject is influenced by the inter-set rest intervals (Ratamess et al., 2012; Tibana et al., 2012). In untrained subjects the rest interval between sets should be sufficient to promote an adequate bioenergetic recovery, facilitate the removal of metabolic waste products, and provide for the reestablishment of force production (Willardson, 2006). Previous studies revealed that shorter rest intervals between sets and exercises (1- versus 3- or 5-min) elicit a more pronounced metabolic (Farinatti & Castinheiras Neto, 2011; Ratamess et al., 2007), hormonal (Bottaro et al., 2009), and cardiovascular stress (de Salles et al., 2009). This may explain the decreased number of repetitions and total training volume found in a RE session using short inter-set rest intervals (Tibana et al., 2012). Metabolic acidosis, ventilation and oxygen uptake responses during dynamic RE are thought to mediate the rating of perceived exertion (RPE) (Mayhan et al., 2008), which could be useful to prescribe and monitor RE (Lagally et al., 2002). In this sense, the validated OMNI-Resistance Exercise Scale (OMNI-RES) is a pictorial representation of numerical categories ranging from 0 to 10 to assess and monitor RPE responses during RE (Robertson et al., 2003). To date, studies examining the effects of rest intervals between sets during RE on RPE have raised controversial results. Woods et al. (2004) examined the effects of 1-, 2-, or 3-min rest intervals on RPE during 3 sets of 10 repetitions at 70% of 10 repetitions maximum (RM) of seated leg extension exercise in physically active subjects. The RPE response increased following the third set as compared with the second and first sets, regardless of rest interval length. Farah et al. (2012) investigated the effect of 30s and 90s rest intervals on RPE between three sets of five exercises (bench press, seated leg extension, seated row, knee curl, and frontal rise) at 50% 1RM in recreationally trained subjects. They observed a higher RPE following 30s as compared with 90s rest interval. Therefore, further studies are necessary to understand the effects of different rest intervals between sets on RPE, especially during whole body RE sessions designed for hypertrophy and strength, which are commonly used in daily practice in untrained subjects.Thus, the aim of the present study was to compare the effect of 1- versus 3-min rest intervals between sets on RPE, number of repetitions, total training volume and fatigue resistance in untrained subjects. The initial hypothesis is that a longer rest interval will result in lower RPE and higher training volume in untrained subjects.Materials and MethodParticipantsTwelve untrained subjects (9 women and 3 men) age 20.7 ± 0.8 years, body mass 73.9 ± 19.3 kg, height 1.7 ± 0.1 m, body mass index 25.2 ± 5.3 kg/m2 and body fat 15.8 ± 6.0 % volunteered for the study. Subjects were classified as untrained according to the American College of Sports Medicine (ACSM), as they had no previous experience with regular resistance training (American College of Sports, 2009). All subjects were healthy and had no orthopedic or cardiovascular diseases. Before taking part in the experimental protocols, subjects were properly informed of all the purposes, procedures, benefits and risks of the study. The study was approved by the Research Ethics committee of Western Kentucky University and all subjects provided written informed consent (HS12-053). The study was conducted in accordance to the Declaration of Helsinki.ProcedureSubjects participated in eight experimental sessions and were asked to refrain from strenuous physical activity during the study. …