Among the different resistance-training devices, elastic bands are a scientific, affordable, easy-to-use option (Aboodarda et al., 2016; de Oliveira et al., 2017; Soria-Gila et al., 2015), which has shown to be as effective as traditional resistance training for improving strength (Behm, 1991). Exercise with elastic bands facilitates the use of different levels of resistance (variable resistance) by modifying the length over which the band is stretched for a given range of motion (Soria-Gila et al., 2015). Well-designed elastic band based exercise programs resulted in increased strength, improved performance in conducting daily activities, independence, and quality of life in older adults (OA) (Delmonico et al., 2007; Mally et al., 2011; Martins et al., 2013; Romero-Arenas et al., 2011; Rieping et al., 2019; Rossi et al., 2017).
Monitoring exercise intensity is an important factor to ensure the safety and efficacy of resistance training in any context of its application, whether used by athletes or in recreational or therapeutic settings (Robertson, 2004). Scales estimating the rating of perceived exertion (RPE) have been successfully used to (a) prescribe training intensities, (b) guide daily training dosages, and (c) track training progress (Gearhart et al., 2009). The use of RPE scales is based on an assumed functional link between the observed physiological, perceptual, and performance responses that according to the basic tenet of Borg's Effort Continua Model, occurs simultaneously when performing physical activities with increases in the intensity of physical activity performance (Borg, 1982). The aforementioned responses have been analyzed separately or in combination to monitor exercise intensity in recreationally trained athletes (Chapman et al., 2019; Lagally et al., 2002) and active OA (Morishita et al., 2019). RPE scales that combine verbal and visual descriptors could result in a better monitoring of the intensity during physical training activities, because combination of different sensory modalities can be necessary in cases where a single sensory or perception modality could provoke an ambiguous or incomplete result (Lalanneab and Lorenceaua, 2004; Small and Prescott, 2005). In consequence, studies that validate cross-modal perception RPE scales are needed for a proper application, even more when different pictorial, numerical, and/or verbal descriptors for specific exercise modes or type of population are used (Mays et al., 2010).
In order to establish concurrent validity of a new category scale to measure perception of physical exertion, one must correlate a criterion or stimulus variables (i.e., physiological and/or performance parameters, as for example heart rate or total weight lifted), with a concurrent or response variable (i.e., RPE from a previously validated scale) (Lagally and Robertson, 2006). Applied force and heart rate has been used in previous studies with different type of participants as a criterion variable to validate a perceived exertion metric (Colado et al., 2012b; 2014; 2018; Robertson et al., 2003; 2005). It should also be considered that when exercising, it is possible to differentiate between a global and peripheral exertional signal. Thus, RPE can be differentiated between anatomically regionalized perceptual signals that are associated with total body effort perception and active limbs as well as the chest and breathing (Colado et al., 2012b; 2014; 2018; Robertson et al., 2003; 2005). The RPE for active muscles (RPE-AM) is usually higher than the RPE for overall body (RPE-OB). It has been demonstrated that measurement of the RPE-AM increases the precision of perceptually based intensity self-regulation during the resistance exercises (Robertson et al., 2003). Both types of exertional perceptions provide useful information for prescription and intensity monitoring purposes (Robertson, 2004).
The application of different intensities during elastic resistance training can be monitored by associating the target number of repetitions, that is specific to a determinate training stimulus, with the width of the grip using and the resulted RPE score expressed at the end of the set (Colado and Triplett, 2008). Explained in greater detail, this means that the exerciser will firmly hold the elastic band estimating the grip width associated with the previously determined number of repetitions, which will be adjusted to the objective of the training and the corresponding local muscular fatigue rating expressed at the end of the set. If participants completed the prescribed repetitions expressing higher perceptual rating than prescribed, they were asked to use a wider grip or change the band according with the requested level of effort. Conversely, a narrowed grip or a "harder" band was used if the participants expressed a lower perceptual rating that prescribed (Colado et al., 2009; 2010; 2012a).
Colado et al. (2012b) validated the modified version of the OMNI-Resistance Exercise (OMNI-RES) scale by Robertson et al (2003) which was specifically designed to assess the perception of effort in young resistance-trained males during elastic band resistance exercises. A few years later, the same research group validated a new perceptual scale, including specific verbal descriptors for monitoring the intensity of the perceptual signal of exertion when exercising with this type of elastic devices (Colado et al., 2014). This approach was expected to be more broadly applicable to a wider range of the population, for example, those who have difficulty using the classical numerical category scales (Rogers, 2006; Tabbers et al., 2004). According to Revilla et al. (2014) and Weijters et al. (2010), it must be highlighted that: (i) Scales with more of five levels or categories are less recommended because decrease the quality of the perception; (ii) Scales without a midpoint must be avoided; (iii) 5-point scales are better for being applied in general population; and (iv) 5-point scales can improve the accuracy in the linear models of interpretation of the information than 3-points scales, thus the 5-point scales providing higher criterion validity.
Over the years, the scale validated by Colado et al. (2012b) was applied in different populations for whom it was not initially validated (i.e., young, healthy, physically active men), as, for example, is the case for OA (Chupel et al., 2017; Gargallo et al., 2018; Gomez-Tomas et al., 2018; Fritz et al., 2018; Fukuchi et al., 2016; Li et al., 2017; Rieping et al., 2019; Smith et al., 2017). Indeed, more recently, Colado et al. (2018) validated the application of the aforementioned scale for use with OA because strength tracking using RPE may be particularly beneficial for this population (Gearhart et al., 2009). However, the scale with verbal descriptors has not yet been validated for application in populations different from that originally used by Colado et al. (2014) (i.e., young, healthy, physically active men), despite have being used with positive results in recent long-term resistance training studies with different populations, including older people (Muntaner-Mas et al., 2017; Picha et al., 2017; Tada, 2018; Texeira et al., 2016; Wasser et al., 2017). Griep et al. (1998) suggested that older and young individuals differ in their willingness and ability to express their experience, and even this could be influenced when there are a wider number of available responses in combination with a complex variety both in the distribution and in the presentation of stimulus intensities. Guidetti et al. (2011) pointed out that: (i) Perceived exertion can be considered a cognitive function that reflects the progressive aging process; (ii) Cognitive decline associated with aging could be a factor that affects the ability to consistently assign numbers to words or even pictures when attempting to describe exercise-related feelings. Griep et al. (1998) pointed out that for OA is difficult using scales for matching their perceptions due to certain limitations in terms of comprehension, vision, memory and concentration. Although OA could respond much easier on a well bounded and labeled graphic rating scale (Griep et al., 1998), as for example this could be the case of the scale validated by Colado et al. (2014). Consequently, to ensure OA's correct use of the pictorial scale proposed by Colado et al. (2014), it should be validated in this specific type of population.
Therefore, the purposes of this investigation were (i) to assess the construct validity of the Resistance Intensity Scale for Exercise (RISE) with TheraBand elastic bands during resistance exercises performed by older people (>60 years); (ii) to examine the concurrent validity of the RISE scale during elastic resistance exercises performed by OA by means of to examine the effect of three different resistance exercise intensities on reported perceptual response, heart rate, and applied force; and (iii) to corroborate the scores reliability that RISE Scale provided when is employed for quantifying the intensity of the elastic resistance training in different sessions performed by OA. It was hypothesized that (i) RISE scale could be used for monitoring intensity during elastic resistance exercises performed by OA in the same way that the OMNI-RES EB has been used so far; and (ii) The RPE-AM obtained with the RISE scale will be higher than RPE-OB during elastic resistance exercises performed by OA.
The investigation used a cross-sectional, perceptual estimation design consisting of one familiarization and two experimental trials. During the session of familiarization, the participants were instructed on how to use both the OMNI-RES EB scale (Figure 1) and the RISE scale (Figure 2). According to Colado and Triplett (2008), Colado et al., (2012b) and Newsam et al. (2005), they also were asked to establish the grip width on the elastic band with...