The intra- and inter-day reproducibility of the FitroDyne as a measure of multi-jointed muscle function

BACKGROUND: The FitroDyne has been used to assess muscle function but its reproducibility has not been determined during traditional multi-jointed resistance exercises. OBJECTIVE: To assess the intra- and inter-day reproducibility of the FitroDyne during traditional resistance exercises. METHODS: Fourteen resistance trained males completed a one repetition maximum (1RM) and three repetitions of bench press, squat and bent-over-row in 10% increments (from 20 to 80%). Replica trials were completed two and 48 hours later. The FitroDyne rotary encoder measured barbell velocity during each repetition from which power output was calculated. RESULTS: For all loads and exercises the intra-day typical error (TE) for peak and mean power, and velocity, respectively, during bench press (8.2-53 W and 2.2-6.9 cm s^-1), squat (13.3-55.6W and 2.4-7.4 cm s^-1), and bent-over-row (14.5-62.8W and 4-10.5 cm s^-1) identified only moderate changes. Bench press yielded poor intra-day reproducibility at 80% 1RM only (CV% = 12.2-17.1), whereas squat and bent-over-row across all loads for peak and mean power and velocity displayed better reproducibility CV% = 2.4-9.0). Inter-day, the TE detected moderate changes for peak and mean power and velocity for all three exercises. Inter-day reproducibility was comparable to intra-day, though improved for bench press 80% 1RM (CV% = 6.1-8.6). CONCLUSION: These data support the use of the FitroDyne at submaximal loads for monitoring moderate changes in muscle function both intra- and inter-day.