Validity and reliability of the Muscular Fitness Test to evaluate body strength-resistance

INTRODUCTION: In periods of confinement, people cannot be assessed in training centers. Therefore, it is essential to have valid and reliable tests to evaluate physical capacities remotely and with their respective valuation tables. OBJECTIVE: To determine the validity and reliability of the Muscular Fitness Test (MFT) to evaluate the body strength-resistance with self-loading in healthy young adults. Secondly, to create qualitative scales to evaluate the different levels of this physical capacity. MATERIAL AND METHODS: 489 participants performed the MFT (test), and 77 performed it twice (re-test). The MFT included 60 seconds (s) of sit-ups, push-ups, deep squats, and burpees, always in that order, with a micropause of 10 s. The validity of the MFT was evaluated with the final heart rate (FHR), % of the reserve HR (%) and Rating of Perceived Exertion (RPE); the reliability included the Coefficient of Variation (CV), Intra-Class Correlation Coefficient (ICC) and the standard error of the mean (SEM) (p < 0.05). The qualitative scales were constructed with the percentiles ≤25: poor, ≤50: fair, ≤75: good, ≤90: very good, and >90: excellent. RESULTS: Participants performed 91.7 ± 26.5 total repetitions, with a FHR of 172.7 bpm (81.7%) and RPE of 8.1; CV = 2.81%, ICC = 0.97 and SEM = 0.77 (p < 0.001). CONCLUSION: MFT proved to be valid and reliable to assess self-loaded body strength-resistance in healthy young adults. The creation of the MFT qualitative scales allows evaluating the level of body strength-resistance in this population.