Effects Of Anchor Scheme On Torque And Neuromuscular Responses During Sustained Isometric Forearm Flexion Tasks

PURPOSE: Few studies have examined the effects of anchor scheme (AS) on torque (TRQ) and neuromuscular (NM) responses during sustained tasks anchored to a rating of perceived exertion (RPE) versus TRQ. Thus, this study examined the effects of AS on the composite, inter-, and intra-individual patterns of responses for TRQ and NM parameters as well as time to task failure (TTF) and performance fatigability (PF = % decline in maximal voluntary isometric contraction [MVIC]) during fatiguing tasks anchored to RPE and TRQ. METHODS: Twelve men (mean ± SD: age = 20.9 ± 2.2 yrs; height = 179.8 ± 5.3 cm; body mass = 80.2 ± 9.9 kg) performed forearm flexion MVICs before and after sustained, isometric forearm flexion tasks to failure anchored to RPE = 4 (RPEFT) and the torque (TRQFT) that corresponded to the TRQ produced during the initial 1 s of the RPEFT. The amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the biceps brachii. Polynomial regression analyses were used to define the individual and composite relationships for the normalized TRQ and NM parameters versus normalized time relationships during the fatiguing tasks. Dependent t-tests were used to determine mean differences for TTF and PF between the fatiguing tasks. RESULTS: The RPEFT had a greater TTF than the TRQFT (p = 0.006). The TRQFT had greater PF than the RPEFT (p < 0.001). During the RPEFT, there were significant (p ≤ 0.05) linear decreases in the composite patterns of responses for TRQ, EMG MPF, MMG MPF, and neuromuscular efficiency (NME), a linear increase for MMG AMP, and no relationship for EMG AMP. During the TRQFT, there were significant (p ≤ 0.05) linear decreases in the composite patterns of responses for EMG MPF, MMG MPF, and NME, linear increases in EMG AMP and MMG AMP, and no relationship for TRQ. The individual patterns of responses for the NM parameters indicated substantial AS-specific inter- and intra-individual variability. CONCLUSIONS: The greater TTF but lower PF following the RPEFT than the TRQFT may be due to the distinct characteristics associated with fatiguing tasks anchored to RPE. The composite and individual responses suggested that the motor unit activation strategies regulating torque production as well as the mechanisms contributing to task termination were AS-specific.