Neuromuscular Fatigue Responses of Endurance- and Strength-Trained Athletes during Incremental Cycling Exercise

Abstract

This study explored the development of neuromuscular fatigue responses during progressive cycling exercise. The sample comprised 32 participants aged 22.0 ± 0.54 years who were assigned into three groups: endurance-trained group (END, triathletes, n = 10), strength-trained group (STR, bodybuilders, n = 10) and control group (CG, recreationally active students, n = 12). The incremental cycling exercise was performed using a progressive protocol starting with a 3 min resting measurement and then 50 W workload with subsequent constant increments of 50 W every 3 min until 200 W. Surface electromyography (SEMG) of rectus femoris muscles was recorded during the final 30 s of each of the four workloads. During the final 15 s of each workload, participants rated their overall perception of effort using the 20-point rating of the perceived exertion (RPE) scale. Post hoc Tukey’s HSD testing showed significant differences between the END and STR groups in median frequency and mean power frequency across all workloads (p < 0.001 and p < 0.01, respectively). Athletes from the END group had significantly lower electromyogram amplitude responses than those from the STR (p = 0.0093) and CG groups (p = 0.0006). Increasing RPE points from 50 to 200 W were significantly higher in the STR than in the END group (p < 0.001). In conclusion, there is a significant variation in the neuromuscular fatigue profiles between athletes with different training backgrounds when a cycling exercise is applied. The approximately linear trends of the SEMG and RPE values of both groups of athletes with increasing workload support the increased skeletal muscle recruitment with perceived exertion or fatiguing effect.

Functional Near-Infrared Spectroscopy-Based Evidence of the Cerebral Oxygenation and Network Characteristics of Upper Limb Fatigue

“…Lower muscle vascular conductance and maximal cardiac output in the upper limb muscles may have contributed to this effect [32]. Consistent with prior fatigue research where the most intense fatigue was observed at the end of exercise [33,34], our participants self-reported an RPE of "very hard" or "exhausted" after upper limb cycling, affirming the successful fatigue induction in this study.…”

It Is Possible to Measure the Internal Training Load Of Resistance Athlete Using the Etrimp Method

“…One of the formulas for obtaining an internal load value using the TRIMP method requires the time in each heart rate zone during a given exercise. Edward proposed eTRIMP method which the ITL result is determines by measuring a product of the accumulated training duration in minutes of 5 HR zones by a coefficient related to each zone (50 to 60% of HRmax x 1; 60 to 70% of HRmax x 2; 70 to 80% of HRmax x 3; 80 to 90% of HRmax x 4; and 90-100% of HRmax x 5), a model which has a relationship moderate to large between measures of training load [2]. Including, since eTRIMP does not require an exercise test, it is more easily implementable in large studies [3].…”