(24) THE EFFECT OF A MEAL REPLACEMENT SHAKE INTERVENTION ON STAIR CLIMB PERFORMANCE IN OVERWEIGHT AND OBESE FIREFIGHTERS

Purpose: Overweight (OW) and obesity (OB) prevalence are higher in firefighters (FF) than the public and may negatively impact occupational task performance (e.g. stair climb [SC] performance). Unpredictable call volumes and times causing irregular eating schedules may impact obesity rates. Meal replacement (MR) shakes offer a practical approach and minimal intervention to consume nutrient dense and reduced energy meals. However, it is unknown how a MR intervention impacts SC performance, a critical occupational task among FF. The purpose of this study was to examine the effect of a MR intervention on SC performance in OW and OB firefighters. Methods: Forty-five OW and OB FF (age:37.5±7.3yrs; stature:179.5±7.2cm; body mass (BM):106.7±20.2 kg; BMI:33.0±4.8 kg/m²) volunteered for a 14-week cluster randomized controlled trial. Stations were randomly assigned to the MR or wait-list control group (CON) to avoid contamination between treatment arms. The MR (stations=11; FF=22) group received commercially available MR shakes (Protein:25g; Carbohydrate:6g; Fat:6g) and consumed 1 per day for the first week and 2 per day for the remaining 13 weeks ad libitum. The CON (stations=11; FF=23) group was asked to continue with their normal diet for the 14 weeks. All FF were asked to maintain their current exercise habits. Visit one involved a study familiarization and visit two (2-10 days after) involved baseline assessments (PRE) of stature, BM, and a dual-energy X-ray absorptiometry scan to assess fat distribution (trunk/legs percent body fat ratio [T/L %BF]). FF were fitted with a heart rate (HR) monitor and weight vest (22.7kg) to complete a SC task involving ascending and descending a flight of stairs 4 times (104 steps). SC time, SC HR immediately post, SC HR 1-min post, and SC HR recovery ([HRrec; SC HR immediately post - SC HR 1-min post) were recorded. After 14 weeks, FF returned for a third visit (POST) at the same time of day (±2hrs) to complete the same protocol. A linear mixed model was used to test whether POST means differed between groups, with PRE values included as a covariate and a random effect for the cluster (i.e., station). Models were run for SC time, SC HR immediately post, SC HR 1-min post, HRrec, T/L %BF, and BM. Partial correlation coefficients were used to explore the relationship between the %∆SC HRrecovery and %∆T/L %BF, while controlling for %∆BM. Results: There were no intervention effects on SC time (P=0.942), SC HR immediately post (P=0.235), or SC HR 1-min post (P=0.074); however, the MR group experienced a greater change in HRrec (MR:-3.7±9.9bpm; CON:+6.1±8.3bpm; P < 0.001), T/L %BF (MR:-0.02±0.05; CON:+0.007±0.03; P=0.036), and BM (MR:-1.4±3.1kg; CON:-0.2±2.6kg; P=0.022) compared to the CON group. A greater %∆ in SC HRrec was associated with a greater %∆ in T/L %BF (r=3.87; P=0.010). Conclusions: The MR intervention did not impact SC time, but did improve HRrec following a SC task. A reduction in the ratio of trunk/leg adiposity, when controlling BM changes, was associated with greater HRrec from SC tasks. It may be speculated that reduced trunk adiposity reduces inflammation and improves HRrec. Practical Applications: MR interventions may be a practical strategy to aid in weight loss, fat redistribution, and improve recovery following strenuous FF tasks. Results provide fire administrators and tactical strength and conditioning practitioners with a minimal nutritional strategy to enhance FF health and performance. Acknowledgements: None