The Effects of Load and Training Pattern on Acute Neuromuscular Responses in the Upper Body

Abstract

The purpose of this study was to examine the effects of repetition maximum (RM) loads and training patterns on acute neuromuscular responses in the upper body. Markers of fatigue were monitored under a descending pattern (DP), in which repetitions decreased in subsequent sets, and an ascending pattern (AP), in which repetitions increased in subsequent sets. Both training patterns were performed using 5- and 10-RM loads. Fatigue was assessed by monitoring changes in force output, motor unit activation and muscle twitch characteristics (peak twitch [PT], time to PT [TPT], and ½ relaxation time [RT]). All 4 protocols (5-RM DP, 5-RM AP, 10-RM DP, and 10-RM AP) produced significant decreases pre to postprotocol in force output, TPT, and ½RT. With the exception of 5-RM DP, all protocols produced significant decreases in motor unit activation. Pre to postprotocol, PT forces were potentiated under 5-RM loads, whereas they were depressed under 10-RM loads. Hence, a main effect for training protocols showed that changes in PT force were significantly different under 5-RM, as compared to 10-RM loads. The results indicate that central fatigue may be independent of load and pattern, whereas peripheral fatigue would appear to be dependent on load but not pattern.

Do the Acute Biochemical and Neuromuscular Responses Justify the Classification of Strength- and Hypertrophy-Type Resistance Exercise?

“…Correction for PV changes revealed significant reductions in plasma Na (from pre20 to post 0) may suggest that there was a gradual reuptake and redistribution of circulating K + during the rest intervals followed by a slight undershoot. Whilst such a notion is consistent with some previous studies (34,36), it is equally viable that the plasma K + concentrations also reflect blood that has perfused inactive muscle, the modifying effects of other ions (e.g., Ca Although the low sample size of the present study should be considered when interpreting the findings, it seems possible that peripheral factors relating to BL and H + accumulation contributed to the fatigue experienced following the present HYP workout, this conclusion is consistent with previous research that has attributed peripheral factors to reductions in performance following HYP workouts (17,19,24). Although greater BL and pH changes were observed following the HYP workout, peripheral fatigue factors cannot be excluded as a reason for the force reductions following the STR workout.…”

“…Even though all these conflicting findings prevent accurate conclusions regarding the neural responses to HYP-type RE, the present EMG data is not at odds with the theory that fatigue following HYP workouts is mainly peripheral in origin (19).…”

“…However, our findings are partly in agreement with a number of studies based on more clinical methods (e.g. Interpolated Twitch Technique) which do not support the popular perception that high loads result in greater neural fatigue (18,19). These findings have been taken to suggest that chronic adaptations resulting from HYP-type RE may result from stress being placed on both the central and peripheral components of the neuromuscular system (19).…”

“…Interpolated Twitch Technique) which do not support the popular perception that high loads result in greater neural fatigue (18,19). These findings have been taken to suggest that chronic adaptations resulting from HYP-type RE may result from stress being placed on both the central and peripheral components of the neuromuscular system (19). Whilst the limitations of surface EMG prevent an accurate interpretation of the present findings, the current combination of intensity, volume and rest intervals should also be considered.…”

“…Significant reductions in muscle activity have been reported following high-intensity/low-volume workouts alongside reductions in force production (15)(16)(17). Although these observations have often been used to support the notion that STR-type RE provides a greater stimulus to the nervous system (1), a number of studies have not observed differences between high and low intensity workouts with respect to their effects on the nervous system (18)(19). The lack of clarity most likely results from the utilisation of distinctly different performance measures (e.g.…”