The control of exercise intensity is a key factor in ensuring the safety and efficacy of physical activity in any context, including athletic, recreational, and therapeutic settings (Robertson, 2004). Simple tools as well as scales of perceived exertion have been created to ensure control of the intensity for a wide-range of exercises performed by a variety of populations (Robertson et al., 2003; 2004; 2005a; 2005b). These scales are fundamental in that there is a functional link between the three kinds of responses that can occur during physical exercise (physiological, perceptual, and performance). Therefore, these responses can be utilized in a combined fashion using perceived exertion scales to monitor exercise intensity (Lagally et al., 2002).
To make it easier to monitor intensity during the prescription and performance of physical exercise, scales have been created for use during aerobic and strength training in a wide range of situations (Robertson et al., 2003, 2004; 2005b). These scales positively relate the rating of perceived exertion (RPE) with certain physiological variables such as blood lactic acid concentration, muscular activity, and heart rate (Lagally et al., 2002; Lepley and Hatzel, 2010; Miller et al., 2009; Rozenek et al. 1993). Such tools have been implemented and validated to control intensity while performing exercises, independently of age (Robertson et al., 2005b). This means that these RPE scales would be useful for health-fitness and clinical practitioners (Robertson, 2004).
Very few studies have used the OMNI perceived exertion scale for resistance exercise (OMNI-RES) (Robertson et al., 2003; 2005b) while carrying out physical conditioning programs with different kinds of materials for strength training (i.e., weight machines; elastic bands and tubing; aquatic devices that increase drag force) (Colado et al., 2009; 2010; 2012a; Colado and Triplett, 2008). However, there is doubt as to whether this kind of scale should be used with materials other than those for which they were validated (i.e., Olympic curl bars and plate-loaded machines) (Robertson et al., 2003).
There has only been one study to date that has carried out concurrent validation of the OMNI-RES for other kinds of materials that are not based on weight for strength training, as is the case with elastic bands (Colado et al., 2012b). Myoelectric activity and heart rate were used as criterion variables, showing that the OMNI-RES can be used for monitoring the intensity of exercise when elastic bands are used. In similar fashion to the OMNIRES scale validated for weight devices by Robertson et al. (2003), the OMNI-RES exercise scale of perceived exertion with elastic bands (OMINI-RES EB) (see figure 1a) has both verbal and mode-specific pictorial descriptors distributed over a comparatively wide response range. However, some researchers believe that it is necessary to assess the perception of effort in different conditions and in different populations to further its usability (Tiggemann et al., 2010). Furthermore, Colado (2004) advised that certain populations can find this kind of scale difficult to use as there are many levels of verbal information and mode-specific pictorial descriptors which are based on linear physiological responses, meaning that it may be necessary to create even simpler, more specific scales that are easier to use during training regimes (Colado et al., 2008; Pincivero et al., 2003). Therefore, the validity would be required to be constructed on a healthy population first before it can be used by those populations that find using the current scales to be difficult.
It is well known that in order to measure the construct validity of a new scale for perceived exertion, it is necessary to correlate the RPE from a criterion scale with the RPE from a conditional scale (Robertson et al., 2004). As the OMNI-Resistance Exercise Scale of perceived exertion with Thera-Band[R] resistance bands used by Colado et al. (2012b) is the only specific scale to have been accepted as a valid perceptual measurement tool due to the statistically significant correlation between physiological and perceptual variables, it seems that this can be used as the criterion metric in order to establish construct validity of a new scale. To establish concurrent validity of a new scale, criterion or stimulus variables must be correlated with a concurrent or response variable (Lagally and Robertson, 2006). In addition, any validation of a new scale should provide information on its effectiveness for controlling the intensity between different training sessions. In addition it must be sensitive enough to differentially measure RPE from active muscle groups as well as the overall body where the criterion variables increased over separate sets of resistance exercise.
Therefore, the purposes of this investigation were (i) To assess the construct validity of a new perceived exertion scale for resistance exercises performed with elastic bands; (ii) To examine the effect of two different resistance exercise intensities with elastic bands on RPE, myoelectric activity, and heart rate responses; (iii) To examine the concurrent validity of the Thera-Band resistance exercise scale for use with elastic bands during isotonic resistance exercises; and (iv) To determine the reliability of the session RPE method, using the Thera-Band resistance exercise scale, for quantifying resistance training with elastic bands. It was hypothesized that (i) the two scales (OMNI-RES EB and Thera-Band[R] resistance exercise scale) could be used interchangeably during resistance exercises with elastic bands; and (ii) that the ratings of perceived exertion for the active muscles and overall body would show a positive link with muscular activation and heart rate during resistance exercises with elastic bands.
Borg's original RPE scales have been modified during the past several decades in an attempt to apply the scales to different settings, populations, and exercises (Mays, 2009). Mays et al. (2010) stated that there are few studies that show evidence of cross-modal application of OMNI ratings of perceived exertion scales, thus providing the justification and necessity for the development of OMNI scales that differ in the pictorial, numerical and/or verbal descriptors for specific exercise modes or type of population. Considering this rationale, the Thera-Band perception of exertion scale for resistance training with elastic bands has five perception levels that range from "Easy" to "Maximal" (Figure 1b). The use of only five intensity levels could be more useful for subjects with only limited resistance training experience (Colado, 2004). Another new feature of the scale is that the values are exclusively expressed as words, which could make it more intuitive to use (Colado and Chulvi, 2008).
According to Mays et al. (2010), for a newly developed RPE scale to be considered a valid metric for use in clinical and health-fitness settings, response validity has to be established which is usually provided by concurrent and construct validity. Therefore, the present study was developed based on these guidelines. Two sets of each exercise (i.e., lateral and frontal raise) were performed at different intensities (low- and high-intensity sets), and subjects used both scales to give their ratings of perceived exertion of active muscles (RPE-AM) and overall body (RPE-O). To demonstrate the construct validity of the new Thera-Band scale, its values were compared with those obtained with the OMNI-RES EB scale while performing the two different exercises. To demonstrate the concurrent validity of the new Thera-Band scale, all dependent variables (EMG, RPE-AM, RPE-O, and heart rate) were compared for the different intensities.
Twenty subjects [12 male and 8 female; 22.00 ([+ or -] 0.76) years; 1.77 ([+ or -] 0.03) m; 69.80 ([+ or -] 2.67) kg; 489.24 ([+ or -] 71.16) min physical activity per week; data expressed as mean (SEM)] participated in this study. The inclusion criteria were: (i) 6 months minimum experience of physical activity and (ii) attendance at weight-training class or participating in weight training exercises at least twice a week for at least 3 weeks before testing. Participants suffering musculoskeletal pain or any neuromuscular and cardiovascular disorder were excluded from the study. All subjects signed an informed consent form before starting the protocol. The review board of the institution approved the study. All procedures applied in this study comply with the...