Feasibility Study of Resistance Training Intervention in Untrained Adolescents

The recruitment process refers to the protocols used to find, select, and enroll participants into a study. The recruitment process for this study was represented by reporting the total number of unique QR code scans from posted flyers and tabling events, the number of completed interest forms, the number of eligible participants and the number of consented participants. A recruitment period of 3 weeks was given for the before and after-school trials.

Sample size was used as another key feasibility marker and refers to the total number of individuals used in the intervention.

Consent rate is often referred to as the percentage of participants enrolled divided by the number of eligible participants. For this study, consent rate was calculated by taking the total number of participants that consented and were randomized divided by the number of eligible students.

Retention rate is defined as the percentage of the total number of randomized participants assessed for primary outcomes and used in the primary outcome analysis. For the purpose of this study, researchers were interested in retention for both primary and secondary outcomes meaning researchers tracked retention from pre-intervention fitness testing, through treatments, and post-intervention fitness testing sessions. The follow up interview was not included in calculating the retention rate. Only participants that withdrew from the study or were not included in the primary and secondary outcome analysis influenced the retention rate. Thus, retention was calculated as the percentage of participants that completed pre and post-intervention fitness assessments and intervention treatment divided by the number of participants randomized into treatment groups.

For this study, fidelity was assessed at the instructor and participant level. Instructor fidelity was measured as a percentage by totaling the provided sessions divided by the total number of planned sessions. An acceptable percentage was set at 80% due to conflicts with events such as holiday breaks or parent teacher conferences. To assess participant fidelity, the primary researcher and participants recorded session durations, completed sets and intensity along with activity and diet audits at weeks 2, and 4 of the intervention. The activity and diet audit included a modified Copper Institute Fitnessgram and Activitygram questionnaire.

Participant attendance was observed by the researcher and measured as attended sessions divided by total sessions offered.

Adverse events were recorded during the intervention by the participants on workout documents and by observations from the primary researcher.

Participant experience was assessed by utilizing the validated short form 4 item Physical Activity Enjoyment Scale (PACES-S) survey for adolescents [48]. Participants answered 4 items including: "I enjoyed it; I find it pleasurable; It is very pleasant; and It feels good" by responding with the five-point Likert scale ranging from 1= "strongly disagree" to 5 = "strongly agree". To further investigators' depth of understanding, participant experience was also assessed by a follow up interview concluding the intervention.

In a separate private room, one participant at a time weighed themselves on a certified scale. Participants used the handheld Omron model HBF-306 to enter their weight, age, sex and activity level. Resulting body mass index (kg/m^2) was recorded.

In a separate private room, one participant at a time weighed themselves on a certified scale. Participants used the handheld Omron model HBF-306 to enter their weight, age, sex and activity level. Resulting body fat percentage data was recorded.

Isometric lower body pull. Using the Baseline 12-0400 Back-Leg-Chest dynamometer participants stood up-right and feet hip width apart on the dynamometer platform with the chain adjusted so the handle was at the intra-articular space of the knee joint. Participants were instructed to grip the handle evenly at the center then produce a maximal 5 sec pull keeping the back from bending and arms straight. Participants were allowed to rest 30 sec between attempts. Participants had one practice attempt for familiarization purposes and then the best score of the three following attempts were recorded.

Participants were paired; participant 1 performed the test while participant 2 recorded the number of push-ups. Participants performed the assessment in accordance with the Cooper Institute's procedures. Participant 1 assumed a prone plank position with hands slightly outside of shoulders, fingers stretched out and legs straight with a slight gap. While performing push-ups, the participants' back maintained a straight line from head to ankles. Participants started by lowering their body until the upper arms became parallel to the ground. The participant then extended their arms straight pushing their body up. This movement was performed every three seconds by metronome and repeated until failure. Participants were allowed one form correction and two form corrections resulted in test termination. Form corrections included participants stopping to rest, a failure to maintain a straight back, achieving proper depth or fully extending the arms.

Participants performed the modified pull-up test in accordance with Cooper Institute's procedure. Participants placed a barbell in a squat rack so that the barbell was one to two inches away from participant's reach while supine on the ground. A band was then placed seven to eight inches below the barbell. Participants started the assessment by overhand gripping the barbell and creating a straight line from head to heels so that only the heels were in ground contact. Participants then pulled their body toward the barbell until the chin was above the band. This movement was performed every three seconds by metronome and repeated until failure. Participants were allowed one form of correction and two form corrections would result in test termination. Form corrections included participants stopping to rest, failure to maintain a straight line, achieve proper depth and fully extending the arms.

To assess cardiovascular fitness, the Progressive Aerobic Cardiovascular Endurance Run (PACER) assessment was used. Prior to the start of assessment, the primary investigator measured and marked a designated 20-meter distance in the gymnasium for testing. Participants were briefed on the assessment guidelines and participated in one practice opportunity prior to the official assessment. Once familiarized, participants ran the 20-meter distance in accordance to PACER cadences from the Cooper Institute for as long as possible. The test was terminated when the participant voluntarily stopped due to fatigue or when two laps were missed. The primary researcher recorded total number of successful levels. Once completed, the primary researcher computed predicted peak VO2 by using VO2peak = 0.353(Laps) - 1.121(Age) + 45.619.