Purpose: The purpose of this study was to examine the effects of joint angle on MVIC and neuromuscular responses at task failure following sustained, isometric forearm flexion tasks anchored to a rating of perceived exertion (RPE) of 8 (RPE = 8) and anchored to the initial torque that corresponded to RPE = 8 (TRQ). Methods: Ten women (age: 21.0 ± 2.8 yrs; height: 168.5 ± 7.2 cm; body mass: 68.0 ± 7.2 kg) performed 2, 3 s MVICs at joint angles (JA) of 75°, 100°, and 125° (randomized order) before and after sustained, isometric forearm flexion tasks to failure at fatiguing joint angles (FJA) of 75° and 125° (dominant arm), anchored to RPE = 8 and TRQ, while electromyographic (EMG) signals were recorded from the biceps brachii (BB). Results: The pre-test MVIC values at JA100 were significantly greater than both JA75 (p = 0.001) and JA125 (p = 0.002). There was no significant (p = 0.369) mean difference in time to task failure (TTF) for FJA75 versus FJA125 when anchored to TRQ, but when anchored to RPE = 8, FJA75 was significantly greater (p = 0.009) than FJA125. For performance fatigability (percent decline in MVIC), JA125 was significantly greater (p < 0.001) than JA75, but not JA100 (p = 0.038). During the fatiguing tasks at FJA75, EMG amplitude (AMP) decreased for JA100 and JA125, and JA100 had a significantly greater (p = 0.004) percent change than JA75. For EMG mean power frequency (MPF), there were decreases for both anchor schemes, but TRQ had a significantly greater (p = 0.003) percent change than RPE = 8. Conclusion: Following the fatiguing tasks at FJA75 (RPE = 8 and TRQ), the decreases in EMG AMP and MVIC at MVIC JA100 and MVIC JA125 suggested that both central and peripheral fatigue contributed to performance fatigability, but for MVIC JA75, the MVIC decrease and increase in EMG AMP were due to peripheral fatigue.
Arnett, Jocelyn E.; Smith, Robert W.; Neltner, Tyler J.; Anders, John Paul V.; Ortega, Dolores G.; Housh, Terry J.; Schmidt, Richard J.; and Johnson, Glen O.
"The Effects of Joint Angle and Anchoring Scheme on Performance Fatigability and Neuromuscular Responses Following Isometric Forearm Flexion Tasks to Failure,"
NeuroSports: Vol. 1:
2, Article 7.
Available at: https://nsuworks.nova.edu/neurosports/vol1/iss2/7