Overview of muscle fatigue differences between maximal eccentric and concentric resistance exercise.

Since the 1970s, researchers have studied a potential difference in muscle fatigue (acute strength loss) between maximal eccentric (ECC max ) and concentric (CON max ) resistance exercise. However, a clear answer to whether such a difference exists has not been established. Therefore, the aim of our paper was to overview methods and results of studies that compared acute changes in muscle strength after bouts of ECC max and CON max resistance exercise. We identified 30 relevant studies. Participants were typically healthy men aged 20-40 years. Exercise usually consisted of 40-100 isokinetic ECC max and CON max repetitions of the knee extensors or elbow flexors. Both ECC max and CON max exercise caused significant strength loss, which plateaued and rarely exceeded 60% of baseline, suggesting strength preservation. In upper-body muscles, strength loss at the end of ECC max (31.4 ± 20.4%) and CON max (33.6 ± 17.5%) exercise was similar, whereas in lower-body muscles, strength loss was less after ECC max (13.3 ± 12.2%) than CON max (39.7 ± 13.3%) exercise. Muscle architecture and daily use of lower-body muscles likely protects lower-body muscles from strength loss during ECC max exercise. We also reviewed seven studies on muscle fatigue during coupled ECC max -CON max exercise and found similar strength loss in the ECC and CON phases. We also found evidence from three studies that more ECC than CON repetitions can be completed at equal relative loads. These results indicate that muscle fatigue may manifest differently between ECC max and CON max resistance exercise. An implication of the results is that prescriptions of ECC resistance exercise for lower-body muscles should account for greater fatigue resilience of these muscles compared to upper-body muscles.