The aim of this study was to assess effects of a short-term resistance program on strength in fit young women using weight machines/free weights or elastic tubing. 42 physically fit women (21.79±0.7 years) were randomly assigned to the following groups: (i) the Thera-Band (®) Exercise Station Group (TBG); (ii) the weight machines/free weights group (MFWG); or (iii) the control group (CG). Each experimental group performed the same periodised training program that lasted for 8 weeks, with 2-4 sessions per week and 3-4 sets of 8-15 submaximal reps. A load cell (Isocontrol; ATEmicro, Madrid, Spain) was used to test the evolution of the Maximum Isometric Voluntary Contraction (MIVC) in 3 different exercises: Vertical Rowing (VR), Squat (S) and Back Extension (BE). A mixed model MANOVA [group (CG, TBG, MFWG) x testing time (pre-test, post-test)] was applied to determine the effect of the different resistance training devices on strength. The only groups to improve their MIVC (p<0.005) were TBG and MFWG, respectively: VR 19.87% and 19.76%; S 14.07 and 28.88; BE 14.41% and 14.00%. These results indicate that resistance training using elastic tubing or weight machines/free weights have equivalent improvements in isometric force in short-term programs applied in fit young women.

The concurrent validity of the OMNI-Resistance Exercise Scale (OMNI-RES) of perceived exertion for use with elastic bands was studied during isotonic resistance exercises. Twenty healthy, physically active subjects completed both familiarization and testing sessions. The criterion variables were myoelectric activity, recorded by electromyography, and heart rate, recorded by a heart rate monitor. The subjects performed 2 separate sets of 15 repetitions in each of the 2 testing sessions and for each of the exercises applied (i.e., frontal and lateral raises). One set was carried out with the separation between the hands gripping the elastic band allowing that 15 repetition maximum to be performed in the selected exercise, whereas the other set was carried out with the separation between hands at +50% of the previous grip. The perceived exertion rating for the active muscles and for the overall body, muscular activity, and heart rate were measured during the final repetition of each set. The results showed significant differences (p ≤ 0.001) in myoelectric activity, heart rate, and OMNI-RES scores between the low- and high-intensity sets and the intraclass correlation coefficient was 0.72-0.76. So it can be concluded that the OMNI-RES can be used for monitoring the intensity of exercises when elastic bands are used. This would allow the training stimulus dosage to be precisely controlled in both the session in progress and between different sessions, and allowing to differentiate between different levels of intensity according to the physical aptitudes and special physiological needs of the subjects.

Screen media usage, sleep time and socio-demographic features are related to adolescents' academic performance, but interrelations are little explored. This paper describes these interrelations and behavioral profiles clustered in low and high academic performance. A nationally representative sample of 3,095 Spanish adolescents, aged 12 to 18, was surveyed on 15 variables linked to the purpose of the study. A Self-Organizing Maps analysis established non-linear interrelationships among these variables and identified behavior patterns in subsequent cluster analyses. Topological interrelationships established from the 15 emerging maps indicated that boys used more passive videogames and computers for playing than girls, who tended to use mobile phones to communicate with others. Adolescents with the highest academic performance were the youngest. They slept more and spent less time using sedentary screen media when compared to those with the lowest performance, and they also showed topological relationships with higher socioeconomic status adolescents. Cluster 1 grouped boys who spent more than 5.5 hours daily using sedentary screen media. Their academic performance was low and they slept an average of 8 hours daily. Cluster 2 gathered girls with an excellent academic performance, who slept nearly 9 hours per day, and devoted less time daily to sedentary screen media. Academic performance was directly related to sleep time and socioeconomic status, but inversely related to overall sedentary screen media usage. Profiles from the two clusters were strongly differentiated by gender, age, sedentary screen media usage, sleep time and academic achievement. Girls with the highest academic results had a medium socioeconomic status in Cluster 2. Findings may contribute to establishing recommendations about the timing and duration of screen media usage in adolescents and appropriate sleep time needed to successfully meet the demands of school academics and to improve interventions targeting to affect behavioral change.