(31) A COMPARISON OF MEASURED VERSUS ESTIMATED METABOLIC EQUIVALENTS DURING THE SLED PUSH EXERCISE ON A COMMERCIALLY AVAILABLE STEP MILL

Pushing heavy objects is a common occupational task for tactical personnel (e.g., fire, police, military. It is therefore important to train and test this ability. It would be beneficial to tactical personnel for equipment to be designed and validated such that training and testing tools could be to measure pushing ability in gym settings.

Purpose: The aim of this investigation was to compare metabolic equivalents (METs) collected via a metabolic cart to estimates provided by a commercially available stepping mill.

Methods: Eleven (n = 6 females; n = 5 males; age: 22±3; Ht: 174.2 ± 10 cm; BM: 77.6 ± 17.5 kg) recreationally active college students volunteered to participate in this study. All subjects were required to be apparently healthy (i.e., be free of any musculoskeletal, metabolic, or cardiorespiratory disorders) and participate in a minimum of 150 minutes of moderate to vigorous activity weekly. All subjects agreed to voluntarily participate and complete an informed consent and healthy history questionnaire prior to participation in this research. Participants were required to visit the laboratory in which this study occurred twice, with a minimum of 24 hours between sessions. During each visit, participants performed the sled push exercise on a commercially available step mill while in Overdrive mode. An exercise protocol was developed for the participants to complete on each exercise session consisting of 20 seconds of work followed by 40 seconds of recovery repeating every minute, on the minute, for a total duration of 6 minutes. Prior to the exercise protocol, participants performed a 5-minute warm-up on the step mill using the normal stair climbing function at a self-selected pace. METs for this exercise bout were calculated using direct measurements of breath-by-breath gas exchange via a metabolic cart. Values calculated from breath-by-breath data were then compared to the estimated values provided by the step mill. RESULTS: Paired-samples t-tests indicated that the mean estimated MET values (m=12.6 ± 0.9-13.4 ± 0.6) were significantly different than the mean measured MET values (m=7.1 ±1.3-10.1 ± 0.8) for the sled push exercise (p < 0.05).

Conclusions: When performing the sled push exercise, the estimated values provided by the commercial step mill were significantly greater than measured values at each time interval assessed using gold-standard techniques. These data suggest current limitations in interpreting physiological data for pushing activities.  PRACTICAL APPLICATIONS: When performing this exercise on the step mill, individuals should be aware that actual oxygen consumption and metabolic expenditure may significantly differ from the values displayed on this piece of equipment. Consequently, characterizing exercise intensity based on estimated maximal heart rate and rating of perceived exertion may provide a more accurate tool for assessing intensity for this particular exercise in overdrive mode.

Acknowledgements: We would like to acknowledge Core Health & Fitness for their partial funding of this study.