There is compeling evidence linking resistance training (RT) to health. Benefits span across a broad range of outcomes with primary effects observed on muscle force and power (American College of Sports, 2009; Geirsdottir et al., 2012). Secondary effects are observed on metabolic control (e.g controling the risk factors related to metabolic syndromes, increase sensitivity to insulin and glucose tolerance (Hotamisligil, 2006)), improved systemic inflammatory response (Calle and Fernandez, 2010), and increased functional exercise capacity with consequent improvement in health-related quality of life (American College of Sports, 2009; Geirsdottir et al., 2012).
The American College of Sports Medicine recommends RT with a frequency of 2-3 days/week with intensities of 60-70% of one repetition maximum (RM) for 812 repetitions to maximize muscular strength (American College of Sports, 2009). Commonly, RT is delivered using dumbbells, barbells and weight machines. The elevated costs associated with the large space requirements of such equipments limit its availability (Ramos et al., 2014).
In the last few years, modalities have been proposed as alternative to deliver RT. The use of elastic resistance (ER) is a method that uses elastic bands / tubes as resistive load (American College of Sports Medicine, 2011; Ramos et al., 2014; Simoneau et al., 2001). Muscle activation measured by electromyography was found similar to both upper and lower limbs during isotonic contractions with the advantage of permiting greater range of motion compared to weight machines (American College of Sports Medicine, 2011; Andersen et al., 2010; Brandt et al., 2013). Aboodarda et al. (2016) performed a meta-analysis of 18 articles with 35 different measures of activation and observed that ER provides similar prime mover, antagonist, stabilizer and assistant movers activation as isoinertial resistance. There is also the advantage to use it in places with limited space including home environment, since the equipaments used on elastic resistance are relatively inexpensive and more portable than weight machines.
Likewise conventional RT, benefits of elastic resistance training are observed on muscle force and exercise capacity in healthy older adults and individuals with different diseases (Martins et al., 2013; Mikesky et al., 1994; Motalebi and Loke, 2014; Ramos et al., 2014; Singnoy et al., 2017; Turban et al., 2014). Behm (1991) conducted the first randomized trial comparing elastic resistance to traditional machine and hydraulic resistance machine during a 10-week training program in young women and concluded that the three training methods were equally effective in promoting strength gains. Similarly, Colado et al. (2010) compared the resistance training using Thera-Band[R] elastic tubes with conventional resistance training in young women and described comparable gains in isometric force in both groups. In middle-aged sedentary women, Colado and Triplett (2008) compared elastic resistance training to conventional RT and found similar benefits in functional exercise capacity and body composition in both groups. Furthermore, Webber and Porter (2010) observed similar improvement in strength and muscle power between ER and conventional RT in mobility-impaired older women.
Therefore, although literature seems decisive about the benefits of ER, the comparability of a resistance training protocol using elastic tubing to conventional resistance training in middle-aged to older healthy adults including men and women, remains to be investigated.
This study compared the effects of resistance training using elastic tubing to conventional resistance training using weight machines on muscle force, functional exercise capacity, and health-related life quality. We hypothesized that RT using elastic tubing promotes similar positive effects to those found in conventional RT in middle-aged to older healthy adults.
In this quasi-randomized controlled trial, middle-aged to older healthy adults (mean age 58 years) were included between March and December 2015. The study was conducted in a university-based, outpatient, physical therapy clinic. Subjects were considered eligible if were older than 45 years old without any underlying cardiac, musculoskeletal or pulmonary disease and were not engaged in regular physical activity program during the last 6 months. Individuals would be excluded if they had low adherence to training (less than 75% of all sessions). All procedures were approved by the Research Ethics Committee (CAAE: 16606213.4.0000.5402) and followed the resolution #466/12 of the National Health Council, Brazil. Written informed consent was obtained from all patients. This study was registered in the Brazilian clinical trials registration (#RBR-4tswsq).
Subjects included in the study followed an initial assessment including medical consultation (including physical fitness test: cardiopulmonary exercise test), identification and assessment of medical history, anthropometric measurements and vital signs, physical activity levels (International Physical Activity Questionnaire - IPAQ questionnaire) (Pardini et al., 2001), health-related quality of life (Medical Outcomes Study 36-Item Short Form Health Survey, SF-36) (Ciconelli et al., 1999), functional exercise capacity (six minute walk test, 6MWT) (Holland et al., 2014), muscle force of upper limbs (UL) and lower (LL) (dynamometry) (Ramos et al., 2014).
After the initial assessment, subjects were allocated into one of three a priori defined groups (ETG = elastic tubing group; CG = control group; CTG = conventional training group). Allocation of the first three individuals occurred via sealed opaque envelopes. All subsequent subjects included in the study were allocated following the sequence of these three individuals (quasi-randomization, sequence: ETG, CG, CTG) (Figure 1).
Individuals in the control group did not receive physical training or formal activity counseling, but were instructed to mantain their daily activities. Patients in ETG and CTG groups performed resistance exercise training for 12 weeks (3x/week) with recuperative intervals of 48 to 72 hours between sessions. After six and 12 weeks of training, patients had their muscle force, functional exercise capacity and health-related quality of life reassessed. Details on muscle force measurements, load progression during the sessions and composition of exercise programs are described below.
Evaluation of muscle force and load increment over the sessions
The measurement of muscle force was performed using a digital dynamometer (Force Gauge[R], model FG-100kg, USA) in the dominant UL and LL and the results were expressed in Newtons (N) (Ramos et al., 2014). Tested muscle groups were knee extensors, knee flexors, shoulder flexors, shoulder abductors and elbow flexors. Recent data confirms validity and reliability of the elastic resistance for muscle testing. (Andersen et al., 2017)
The criterion to increase workload was based on the number-of-repetitions test (NR) performed at the beginning of each session. Participants performed the NR to verify the maximum number of repetitions they could perform with a given load. The load would be maintained for that session when the maximum number of repetitions performed was 15 [+ or -] 2, it would be otherwise adjusted to achieve the expected number of repetitions. The increment in the ETG was done by changing the diameter of the tubes and/or adding extra tubes. Increases in the workload for subjects in CTG followed the same criterion of ETG with changes in the weights of...