Despite the extensive benefits of physical activity, a large proportion of the world's population remain inactive (18). Approximately 80% of adolescents are not accumulating at least 60 minutes of moderate-to-vigorous physical daily, of which 2–3 d·wk−1 should involve muscle strengthening activities (18). Resistance training is activity designed specifically to enhance muscular fitness (i.e., muscular strength, power, and endurance) by progressively increasing the workload placed on the muscles (15). Resistance training with qualified instruction and supervision is now recognized as a safe, effective, and worthwhile activity for adolescents (8,15,17,21), and numerous studies have demonstrated the health- and fitness-related benefits of resistance training for children and adolescents, which include increased muscular fitness (9,16,25,39), decreased body fat (9,39), improved blood lipid profiles (9), and positive changes in physical self-concept (29,39).
Resistance training programs are typically evaluated using product type fitness tests that assess muscular strength and local muscular endurance. There have been concerns regarding the use of fitness testing with children and adolescents, such as their lack of validity and reliability and the potential stigmatization of children (10,40). However, if used appropriately, fitness testing can help (a) support children's understanding of the effects of activity on fitness, (b) facilitate the learning of physical fitness concepts, (c) provide useful information to parents on their children's health status, and (d) children link health-related fitness to present and future health status (40). Despite these potential contributions, existing fitness tests are product measures that do not provide feedback on actual movement skill technique. Alternatively, process-oriented assessment involves assessing the presence or absence of the criteria you needed to successfully complete an exercise or skill (i.e., your technique).
Although there are existing process measures for identifying injury risk factors in athletes (37), to our knowledge, there are no validated movement skill batteries for evaluating resistance training skill competency. Therefore, the aim of our study was to develop and assess the test-retest reliability and construct validity of the Resistance Training Skills Battery (RTSB) for adolescents. The RTSB was designed to serve the following purposes: (a) evaluate the efficacy of school- and community-based resistance training programs, (b) assess individual progress and provide feedback in resistance training programs, and (c) use as a measurement instrument in research focusing on movement skill competency.
Experimental Approach to the Problem
Fourteen experts in youth resistance training were contacted to determine their willingness and availability to assess the content validity of the RTSB. Each of the experts had a doctorate degree in a relevant field (e.g., kinesiology, exercise physiology, physical education [PE]), had published in international refereed journals and was currently employed at an Australian, American, British, or Canadian university or college. Eight experts responded and provided feedback on the instrument within 8 weeks of the original mailing. Experts were provided with a copy of the RTSB and asked to comment on the following: (a) the importance of developing a resistance training skill battery, (b) the selected resistance training exercises, and (c) the skill performance criteria for each skill identified by the research team. Feedback from experts was then collated and the necessary modifications were made to the original measure. Examples of modifications include: consistency in the number of repetitions for each exercise, changes to the exercises, addition/removal of performance criteria, and the inclusion of pictures depicting the different exercises.
The 6 exercises included in the final RTSB (i.e., body weight squat, push-up, lunge, suspended row, standing overhead press, and front support with chest touches) were chosen because (a) they were considered safe and developmentally appropriate for adolescents, (b) they require minimal equipment and access to facilities, and (c) they represent the movements commonly used in adolescent resistance training programs (8,16,21). Competency in these movements will provide the foundation for developing physical strength in a range of bodily movements, notably (a) trunk stability (front support and chest touches), upper-body pushing strength (push-up), upper-body pulling strength (suspended row), lower-body bilateral strength (squat), and lower-body unilateral strength (lunge). Furthermore, exercises such as the body weight squat, standing overhead press, and push-up provide the foundation for more advanced lifts, including the clean and jerk and bench press. The 6 exercises included in the RTSB target the major muscle groups: lower body (squat/lunge), chest, back and arms (push-up and suspended row), shoulders (standing overhead press), and core (front support with chest touches). Finally, the RTSB was designed to be administered in a school setting and does not require access to a gymnasium or weight room but requires a bar (e.g., wooden bar or plastic pipe) and a suspended bar or suspension straps and an anchor point for administration.
Study approval was sought and obtained from the University of Newcastle Research Ethics Committee, the Newcastle and Maitland Catholic Schools Diocese, and the school principal from 1 secondary school in Newcastle, NSW, Australia. Information letters, parental permission forms, and participant assent forms were sent home with students and those who returned signed forms were permitted to participate in the study. Eligible participants were school students in year 7–10 (aged 12–16 years) from the study school (Table 1). The final sample included 44 boys and 19 girls (mean age = 14.5 ± 1.1 years). Participants were ineligible if they had a medical condition or physical injury preventing testing or training, as self-reported by parents and participants before start of study.
Assessments were conducted by trained research assistants at the study school on 2 occasions 7 days apart (trial 1 and trial 2, hereafter called T1 and T2). On muscular fitness tests, a 7-day separation period is commonly used (30). A period of 1 week was considered as sufficient time to reduce the learning effect of the testing procedures without introducing additional error because of maturation. All research assistants participated in a full-day training workshop in preparation for the assessments.
Participants completed the assessments at school during the same time of day (i.e., between 9 AM and 3 PM) for T1 and T2 in gender-matched groups (i.e., all boys or all girls) of 3 or 4. Participants completed the exercises individually under the supervision of the research assistant. Standardized warm-up activities were not performed before participants completed the RTSB because all of the exercises included body weight resistance or a bar with no weight. Before performing each skill, participants observed demonstrations by a research assistant and only questions pertaining to the exercise protocol (e.g., number of repetitions) were permitted. General encouragement was provided by the research assistants, but no skill-specific feedback was provided at T1 or T2. Participants completed 2 trials of 4 repetitions for each skill in the following order: (a) body weight squat, (b) push-up, (c) lunge, (d) suspended row, (e) standing overhead press, and (f) front support with chest touches. Participants were given 20–30 seconds to recover between trials and also between exercise skills (total time taken to complete the RTSB was 8–10 minutes per participant). All skills were recorded using a digital video camera positioned at a 45° angle to the participant to enable front- and side-on views. This was considered the best viewing position to enable the assessor to properly evaluate each skill during video analysis.
The structure and scoring format of the RTSB were based on the Test of Gross Motor Development 2 (38). Each of the exercises in the RTSB includes 4 (push-up and suspended row) or 5 (body weight squat, lunge, standing overhead press, and front support with chest touches) performance criteria. A full description of the exercises and their corresponding performance criteria is included as Supplemental Digital Content 1 (http://links.lww.com/JSCR/A6). An experienced research assistant, who held a Bachelor's degree in PE and had over 5 years of resistance training experience, assessed all of the skills in this study. Before assessing the skills, the research assistant and the lead investigator viewed a sample of videos to establish what was considered “acceptable” for each of the performance criteria for the 6 skills. For example, this involved identifying what was considered to be an acceptable level of lateral movement (∼10 cm) in the front support with chest touches exercise. This information was then used to identify participants (3 for each skill level) with high (i.e., all criteria performed correctly), moderate (i.e., most criteria performed correctly), and low (i.e., few criteria performed correctly) resistance training skill competency. These examples were then used as a reference and the research assistant was encouraged to review these examples before scoring the videos.
As participants may require several repetitions before they demonstrate a skill to their best ability, scoring of the RTSB was based on their “best repetition technique.” This was defined as the repetition during which the participant satisfied the highest number of performance criteria. For example, if the participant satisfied 2 of the criteria on their first repetition and then 3 criteria on their second repetition, they were awarded a score of 3 for the trial. Participants were awarded a 1 for each performance criterion that was correctly demonstrated and a 0 if the criterion was not performed appropriately. Scores of 0.5 were not awarded. Totals for the 2 sets were added to obtain a raw score for each skill (i.e., a total of 8 for skills involving 4 criteria and 10 for those involving 5 criteria). To ensure that there was not a learning effect between set 1 and set 2, the difference in group (i.e., boys and girls) means was calculated. For girls, the difference between sets ranged from 0.1 for the push-up to −0.1 for the suspended row. For boys, the difference between sets ranged from −0.2 for the lunge to 0.1 for the push-up. Overall, these findings do not support the existence of a learning effect. The skill scores were then added to create a resistance training skill quotient (RTSQ) (possible range, 0–56).
As there are no existing measures for assessing youth resistance training skill competency, it was not possible to assess the criterion validity of the RTSB. However, we tested the construct validity of the RTSB by examining the relationship between overall resistance training skill competency (i.e., RTSQ) and a muscular fitness score (MFS), which combined participants' results for the handgrip strength, timed push-up, and standing long jump tests (2). It was hypothesized that resistance training skill competency would be positively associated with muscular fitness thereby providing a rationale for the assessment of resistance training technique. Relative values (i.e., participant result divided by their body weight) for the handgrip test were first computed to account for differences in body size. Values were then standardized using the following formula: standardized value = (value minus the group mean) divided by the SD of the group. The MFS was then computed by summing the standardized values of the grip strength, timed push-up, and standing long jump tests. These tests were selected because they have good test-retest reliability (23,32) and validity when assessed against upper- and lower-body criterion muscle strength measures in adolescents (20).
Body mass was measured in light clothing without shoes using a portable digital scale (Model no. UC-321PC, A&D Company Ltd, Tokyo, Japan) to the nearest 0.1 kg, and stature was measured to the nearest 0.1 cm using a portable stadiometer (Design No. 1013522; Surgical and Medical Products, Seven Hills, Australia). Body mass index was calculated using the standard equation (body mass [kg]/stature [m2]), and the International Obesity Task Force (IOTF) cut-points were used to classify participants as healthy weight, overweight, or obese (11).
Strength of the hand and forearm muscles was assessed using a grip dynamometer (Smedley's dynamometer; TTM, Tokyo, Japan). The grip-span was adjusted to suit the hand size of the participant before performance. Subjects were asked to squeeze the dynamometer continuously as hard as possible for 2–3 seconds with the elbow in full extension down by the side of the body. The test was performed 3 times each for the left and right hands, alternating hands after each trial. The score in kilograms was recorded. The average of the scores for the right and left hands was used in the analysis.
The 90° angle timed push-up test was used as a measure of upper-body muscular endurance. Testing procedures were explained to the participants before the test. The test began with participants in the push-up position with hands and toes touching the floor, arms approximately shoulder width apart and back straight. Participants lowered themselves to the floor in a controlled manner until a 90° angle was formed at the elbow then pushed back up. Push-ups were performed in time with a metronome, which was set at 40 b·min−1, allowing for 1 push-up every 3 seconds. The test concluded when participants either failed to lower themselves to the required depth on 3 nonconsecutive repetitions (warnings verbalized by assessor), failed to maintain the movement in time with the metronome, or on volitional failure. Assessors did not provide verbal encouragement during the conduct of the test.
Muscular power was assessed using the standing long jump test. Testing procedures were explained to participants before performance. Subjects began with their toes behind a line marked at zero centimeter and performed a maximal long jump, taking off and landing with 2 feet. The distance reached (in cm) in line with the heel of the rearmost foot was recorded. The test was performed twice separated by a rest period of ∼10 seconds. The average of the 2 scores was used in the analysis.
Statistical analyses were completed using PASW Statistics 17 (SPSS, Inc., Chicago, IL, USA) software and alpha levels were set at p ≤ 0.05. Intertrial differences were calculated by subtracting T1 from T2, and independent samples t-tests were used to explore gender differences for intertrial differences. Three types of reliability were assessed: rank order repeatability, change in mean, and typical error. Intraclass correlation (ICC) was used to provide an estimate of rank order repeatability. Intraclass correlation provides an indication of how well the ranking (i.e., from lowest value to highest value) of participants in 1 trial is replicated in subsequent trials. For this study, an ICC > 0.70 was considered to be acceptable. Change in mean was assessed using paired samples t-tests to identify systematic (e.g., learning or maturation effects) and random change in trial results. Bivariate correlations between the intertrial difference (T2−T1) and the mean of the trials [(T2−T1)/2] were used to explore proportional bias. Finally, typical error (i.e., standard error of measurement) was used to explore within-subject variation. Atkinson and Nevill (3) have argued that researchers should consider the purpose of their measures before determining the appropriate degree of error. The RTSB was primarily developed to evaluate the efficacy of school- and community-based resistance training programs. Therefore, it requires the sensitivity to detect small improvements in both individual skills and overall skill competency. Because each resistance training skill is performed twice and the performance criteria are summed for each skill (i.e., a score of 8 or 10), an increase of 2 units represents an improvement in 1 key performance criteria for 1 skill. Similarly, an increase in 6 units on the RTSQ indicates an improvement in 3 performance criteria (e.g., 3 from 1 skill or 1 from 3 skills). Therefore, we suggest that the RTSB requires the sensitivity to detect a difference of 2 for the individual skills and 6 for the RTSQ. The construct validity of the RTSB was tested using multiple regression modeling. Age, gender, and RTSQ scores were included as independent variables in the regression model, whereas MFS was the dependent variable. Age was not significantly associated with MFS and was subsequently removed from the final model.
No injuries or adverse events occurred during assessments. Based on the IOTF cut-points, 36 (81.8%) of the boys and 14 (73.7%) of the girls were classified as healthy weight (Table 1). Eight boys and 5 girls were considered to be overweight. Mean values, SDs, and intertrial differences for the individual skills and the RTSQ are reported in Table 2. The intertrial difference for the RTSQ was significantly higher in girls (−1.7) than in boys (0.3). Girls' scores ranged from 4–10 (of 10) for the squat to 33–52 (of 56) for the RTSQ. Boys' scores ranged from 3–10 (of 10) for the chest touches to 36–53 (of 56) for the RTSQ.
The ICC estimates, changes in mean, and typical error are reported in Table 3. The ICC values for individual exercises ranged from 0.67 (95% confidence interval (CI), 0.54–0.80) for the standing overhead press to 0.87 (95% CI, 0.78–0.92) for the suspended row. The ICC for the RTSQ was 0.88 (95% CI, 0.80–0.93).
The change in mean was small (range, −0.4 to 0.3) but statistically significant for the lunge and suspended row. There was some evidence of proportional bias for the front support with chest touches, indicating that the intertrial difference was inversely related to the mean of trials (r = −0.26, p ≤ 0.05). The typical error of the individual skills ranged from 0.6 for lunge and suspended row to 1.2 for the body weight squat and front support with chest touches. Typical error for the RTSQ was small (RTSQ = 2.5; 95% CIs, 2.1–3.0).
The final regression model explained 39% of the variance in MFS (p ≤ 0.001). Both gender (r = 0.52, p ≤ 0.001) and RTSQ (r = 0.40, p ≤ 0.001) were significantly associated with MFS, suggesting that participants with higher levels of resistance training skill competency scored higher on the tests of muscular fitness.
The aim of this study was to develop and assess the reliability and validity of the RTSB for adolescents. Based on feedback from 8 experts in pediatric resistance training and movement skill development, the final measure included 6 skills representing the basic movements commonly used in youth resistance training programs. Our findings suggest that the RTSB can be used to reliably rank adolescents on their overall resistance training competency and has the necessary sensitivity to detect improvements in resistance training skill proficiency in adolescents. Furthermore, findings indicate that the RTSB has acceptable construct validity based on the significant association between skill competency and muscular.
The importance of developing correct resistance training technique is emphasized in position statements from the American Academy of Pediatrics (1), the Australian Strength and Conditioning Association (4), the Canadian Society for Exercise Physiology (8), the National Strength and Conditioning Association (16), and the United Kingdom Strength and Conditioning Association (21). To our knowledge, this is the first resistance training skills test for adolescents. Although injury rates from supervised youth resistance training are relatively low, using incorrect technique with unsafe behavior may increase the risk of both minor and serious injuries (1,17,27). It seems prudent for adolescents to develop proficiency in basic resistance training skills such as those included in the RTSB before progressing to more advanced exercises. Moreover, progression in a resistance training program should be based on technical proficiency and an understanding of fundamental resistance training principles. For example, PE lessons taught by qualified teachers could address the importance of developing proper exercise technique, and the RTSB could be used to assess students' resistance training skill competency over a semester.
The RTSB was primarily conceived as a tool for assessing the efficacy of school- and community-based resistance training programs. Based on the changes in mean and typical error results, the RTSB can be used reliably to detect small changes in individual skills and overall resistance training competency. There was some evidence of systematic bias for the lunge and suspended row, as observed by a significant increase between trials for the lunge and a significant group decrease for the suspended row. Although statistically significant, these differences are not considered to be clinically meaningful (difference = 0.3 for the lunge and difference = −0.3 for the suspended row). The importance of discussing reliability findings in terms of practical and or clinical significance has been noted in the sports science literature (19). The change in mean and typical error was small for the individual skills (typical error ≤1.2) and the RTSQ (typical error ≤2.5). In recent years, there has been an increase in the number of studies evaluating the effects of school- and community-based resistance training programs for both healthy weight (14,22,25,39) and overweight/obese youth (28). These studies typically report their effect on muscular fitness, body composition, metabolic health, and sometimes psychological well-being. Assessment of resistance training competency may provide additional evidence for program efficacy and learned behaviors. We also suggest that pediatric researchers, health care providers, and PE teachers use the RTSB to provide constructive feedback to participants, which will likely enhance performance, motivation, and self-concept.
The RTSB was designed to be used in pediatric research focusing on the importance of resistance training skill competency. The construct validity of the RTSB and its capacity to reliably rank participants (i.e., from least to most skillful) have implications for researchers and practitioners interested in the psychological and physiological benefits of resistance training competency. In this study, resistance training skill competency (i.e., RTSQ) was significantly associated with muscular fitness, suggesting that more skilled adolescents performed better on the tests of muscular fitness. This is an important finding and provides evidence for the construct validity of the measure. Importantly, resistance training skill competency was significantly associated with fitness after controlling for gender. Competency in a range of fundamental movement skills (FMSs; e.g., running, leaping, throwing, kicking) is considered to provide the foundation for a physically active lifestyle (5,6,24) and as children progress from participating in traditional team sport activities to lifetime physical activities, studies examining the relationship between skill competency and health outcomes may provide additional evidence for the benefits of regular participation in resistance training activities during childhood and adolescence. Furthermore, longitudinal studies may assess the relationship between changes in resistance training skill competency and rates of physical activity-related injury in young people.
Self-determination theory (SDT) (12) and the exercise and self-esteem model (EXEM) (34) describe the importance of competence and how it influences motivation and self-concept. According to SDT, perceived competence is 1 of 3 basic psychological needs that drive intrinsic motivation (12), which has been found to influence physical self-concept in young people (35). Similarly, the EXEM (34) proposes that beliefs about one's ability to perform specific exercises or training activities generalize to a broader perceived physical competence. Providing participants with quantifiable feedback regarding their resistance training competency may help satisfy their basic psychological needs and increase their intrinsic motivation for exercise. This information may complement feedback from fitness test results and provide additional information for self-monitoring (including goal setting), which has been identified as an important strategy for promoting physical activity in young people (13,36). For example, Dishman et al (13) demonstrated that physical activity self-management strategies (e.g., thoughts, goals, plans, and acts) mediate the relationship between self-efficacy and behavior in adolescent girls. This finding suggests that adolescent girls with high levels of self-efficacy are more likely to self-monitor their physical activity behavior, which, in turn, is associated with more physical activity. Providing adolescents with feedback on their resistance skill competency and encouraging them to set performance goals (i.e., competency goals) may improve their exercise self-efficacy and their exercise adherence, indirectly through self-monitoring. Studies examining the role of resistance training skill competency on physical activity self-efficacy and behavior in experimental studies are needed to further explore these hypotheses.
Interestingly, popular fitness test batteries such as FITNESSGRAM (Cooper Institute, Dallas, TX, USA), which was designed to promote lifelong physical activity and fitness, do not include process measures of FMS competency or more specific measures of resistance training competency. This is disappointing because both perceived (6) and actual movement skill competency (7) are important determinants of physical activity behavior in young people. Based on anecdotal evidence from the research assistants, the adolescents enjoyed completing the process-oriented RTSB. Because the performance criteria were not revealed publicly, the testing environment was more consistent with a mastery climate. Evidence suggests that adolescents who perceive their PE lessons as having a mastery climate are more intrinsically motivated to participate (33). Alternatively, a performance climate in PE is associated with less self-determined forms of motivation (31). In traditional fitness testing lessons, effort and ability are on public display, which can be a source of anxiety for some students (10). It may not be feasible for teachers to assess students' skills using video cameras in class; however, it is possible that qualified PE teachers and/or research assistants may be trained to reliably assess skills live in the school setting as is commonly done in the motor assessment literature. As new technologies emerge, real-time assessment and feedback of students' movement skills may become possible using portable digital devices (e.g., smartphones and tablets).
It should be emphasized that our findings may not be generalizable to youth with pathologies or physical injury. Also, our study sample was relatively small and not representative of all adolescents. All of the skills in this study were assessed by the same research assistant in a relatively homogenous group of adolescents. Further work is needed to determine to test the validity and reliability of the RTSB with different adolescent populations and researchers.
Considering the importance of muscular fitness for young people (26) and the popularity of youth resistance training programs, the development of a RTSB that was purposely designed to assess exercise movement competency is a valuable tool for researchers and practitioners. Based on our findings, the RTSB can be used by researchers and practitioners in school- and community-based resistance training programs to evaluate intervention effects and provide additional information for participants to enhance their exercise adherence. This study has demonstrated the construct validity and test-retest reliability of the RTSB in a sample of adolescents. The RTSB can reliably rank participants in regards to their resistance training competency and has the necessary sensitivity to detect small changes in resistance training skill proficiency.
The authors would like to thank the following content experts for providing feedback on the Resistance Training Skills Battery: Dr. Baraket Falk, Dr. David Behm, Dr. Amanda Benson, Dr. Tim Gabbett, Dr. Gerry Naughton, Dr. Rhodri Lloyd, Dr. Sophia Nimphius, Dr. Grant Tomkinson, and Dr. Natasha Shranz. The authors would like to thank Ben Mulligan, Tara Finn, Kathryn Riley, and Sarah Costigan for their assistance in data collection and entry. The authors would also like to thank St. Mary's High School, the school students, and parents for supporting this study.
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