Feasibility of a Train-the-Trainer Delivered Exercise Intervention in Firefighters

Change in cardiorespiratory fitness as measured by VO2 peak during cycle ergometry

Cardiorespiratory fitness will be measured by peak oxygen consumption (VO2 peak). All participants will perform a cycling ergometer test with respiratory gases continuously monitored with open-circuit spirometry (True One 2400®, Parvo-Medics, Inc., Provo, UT). Data will be averaged over 15-second intervals, with the highest 15-second oxygen consumption recorded as the VO2 peak.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Change in body composition as measured by % body fat from a 4-compartment model

Body composition will be evaluated to determine the effects of the intervention on % body fat. Dual-energy x-ray absorptiometry (DXA;General Electric Lunar iDXA, Chicago, IL) and bioelectrical impedance spectroscopy (BIS; ImpediMed SFB7, Queensland, AU) will be used to determine a gold-standard DXA-derived four-compartment model of % body fat.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Change in explosive muscle strength as measured by dynamometry

All participants will perform a rapid and maximal isometric muscle action on a calibrated isokinetic dynamometer (CSMi, Stoughton, MA) against a padded and stiff lever arm for 3-4 seconds. The peak rate of torque development will be determined from the peak of the first derivative of the torque-time curve.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Change in low-back muscular endurance as measured by a modified Biering-Sorensen test

Low-back muscular endurance (time to task failure) will be examined using a modified version of the Biering-Sorensen test, using a variable angle Roman chair (Powerlift, Jefferson, IA).

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Change in balance as measured by a modified star excursion balance test

Balance will be determined by using a modified star excursion balance test. Following a familiarization, participants will reach with their free limb as far as possible in the anterior, posterolateral, and posteromedial direction relative to the stance leg. Scores will be normalized to leg length.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Fidelity of the neuromuscular warm-up as measured by a rubric across sessions at Week 2

The fidelity of the neuromuscular warm-up will be examined using a scoring rubric. The rubric evaluates the leadership abilities of the trainers and the execution of the exercises by the firefighters. Each item is scored 1 to 5 with 1 indicating no correctness and 5 indicating complete correctness. Items will be summed for a total score. Higher values mean higher fidelity.

Time frame: 2 weeks (i.e., beginning of intervention following train-the-trainer completion)

Fidelity of the neuromuscular warm-up as measured by a rubric across sessions at Week 6

The fidelity of the neuromuscular warm-up will be examined using a scoring rubric. The rubric evaluates the leadership abilities of the trainers and the execution of the exercises by the firefighters. Each item is scored 1 to 5 with 1 indicating no correctness and 5 indicating complete correctness. Items will be summed for a total score. Higher values mean higher fidelity.

Time frame: 6 weeks (i.e., one of last 2 sessions)

Fidelity of the HIIT protocol as measured by rate of peak power output across sessions at Week 2

Fidelity will be assessed to ensure participant adherence to the intervention protocol in each session. The fidelity of the HIIT protocol will be examined by recording the prescribed peak power output (90-110%) during the training session. Training intensity will be established from a percentage of the baseline peak power output (Watts) achieved during the VO2 peak test. Higher fidelity is indicated as the percent power output more closely approaches the prescribed power output percentage.

Time frame: 2 weeks (i.e., beginning of intervention following train-the-trainer completion)

Fidelity of the HIIT protocol as measured by rate of peak power output across sessions at Week 6

Fidelity will be assessed to ensure participant adherence to the intervention protocol in each session. The fidelity of the HIIT protocol will be examined by recording the prescribed peak power output (90-110%) during the training session. Training intensity will be established from a percentage of the baseline peak power output (Watts) achieved during the VO2 peak test. Higher fidelity is indicated as the percent power output more closely approaches the prescribed power output percentage.

Time frame: 6 weeks (i.e., one of last 2 sessions)

Change in physical activity as measured by the International Physical Activity Questionnaire-Short Form

Physical activity will be examined using the validated 7-day recall International Physical Activity Questionnaire-Short Form. Higher scores represent greater total metabolic equivalent of task (MET) minutes of physical activity per week based on the following estimates: 3.3 MET units for walking, 4.4 MET units for moderate activity, 8 MET units for vigorous activity. Total MET minutes of physical activity is calculated from the questionnaire using the following calculation: Total MET-min/week = (Walk METs\*min\*days) + (Mod METs\*min\*days) + Vig METs\*min\*days) The study will test whether there is a BASELINE-to-POST increase in total scores on the International Physical Activity Questionnaire-Short Form (units: MET minutes/week) for the TRAINER group relative to the waitlist control group. The outcome for each group is computed as the main of the difference of the POST score minus the BASELINE score.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)

Change in nutrition as measured by the Rapid Eating Assessment for Participants-Short Form

Nutritional habits will be examined using the validated Rapid Eating Assessment for Participants-Short Form. Responses of 'usually/often' receives 1 point, 'sometimes' receives 2 points, and 'rarely/never or does not apply to me' receives 3 points. Possible scores ranged from 13 to 39 with a higher score indicating better nutritional habits. The study will test whether there is a BASELINE-to-POST increase in total scores on the Rapid Eating Assessment for Participants-Short Form for the TRAINER group relative to the waitlist control group. The outcome for each group is computed as the main of the difference of the POST score minus the BASELINE score.

Time frame: Baseline (i.e., pre-intervention), 7 weeks (i.e., post-intervention)