Data reproducibility from an inertial kinetic exercise machine.

An inertial kinetic exercise (IKE, Oconomowoc, WI, USA) machine was created that permits high-velocity workouts suited for injury rehabilitation and speed development in athletes. In addition, its design does not entail the movement of resistance against Earth's gravitational pull. Thus, the design and operation associated with the IKE may be incorporated into novel environments such as space flight. Yet before it can be used for such reasons, IKE data reproducibility must first be ascertained, which serves as the present study's purpose. Methods to assess data reproducibility required subjects (n = 42) to perform 2 IKE elbow flexor trials, each comprising two 60-second sets separated by a 90-second rest. Preceded by a familiarization session on the IKE, subjects were instructed to perform high-speed elbow flexor trial repetitions in good form. Instrumentation entailed an accelerometer and a computer interfaced with software. Maximum and average forces (MF, AF), as well as work (W), were examined for reproducibility with several test-retest measures. Results showed high reproducibility, yet intertrial variability was greater due in part to the length of time between exercise sessions. It was concluded that MF reproducibility was inherently less partly due to the nature of the variable, which entailed a single instantaneous expression over each 60-second set. In contrast, AF and W denoted a cumulative, and thus better overall, representation of total exercise performance. Based on our high reproducibility values, present IKE instrumentation methods appear to be appropriate. Practical applications suggest that coaches and therapists may want to employ an IKE as instrumented in the present study to derive reproducible performance data on people who may use the device under their supervision.