Muscle conduction velocity, strength, neural activity, and morphological changes after eccentric and concentric training

Abstract

This study compared the effects of concentric and eccentric training on neuromuscular adaptations in young subjects. Twenty-two men and women were assigned to one of two groups: concentric (CON, n = 11) and eccentric (ECC, n = 11) training. Training consisted of 6 weeks of isokinetic exercise, performed twice weekly, starting with two sets of eight repetitions, and progressing to five sets of 10 repetitions. Subjects were tested in strength variables [concentric, eccentric, and isometric peak torque (PT), and rate of force development (RFD)], muscle conduction velocity (CV), neuromuscular activity, vastus lateralis (VL) muscle thickness, and echo intensity as determined by ultrasonography. There were similar increases in the concentric and eccentric PTs in both the CON and ECC groups (P < 0.01), but only the ECC group showed an increase in isometric PT (P < 0.001). Similarly, both groups exhibited increased VL muscle thickness, CV, and RFD, and reduced VL echo intensity (P < 0.05). Significant correlations were observed among the relative changes in the neuromuscular outcomes and training variables (e.g., total work, average PT) (r = 0.68-0.75, P < 0.05). The results showed that both training types similarly improved dynamic PT, CV, RFD, and muscle thickness and quality during the early weeks of training.

Stretch imposed on active muscle elicits positive adaptations in strain risk factors and exercise‐induced muscle damage

“…Statistical significance for all tests was accepted at P < 0.05. 23,31,32 To ensure adequate statistical power for all analyses, power analysis was conducted for tendon stiffness (ie, the variable with the smallest effect size) using the following parameters (variable = tendon stiffness, power = 0.80, alpha = 0.05, effect size = 1.1, attrition = 20%). The analysis revealed that the total sample size required for statistical power was 22, thus 28 subjects were initially recruited to account for possible attrition.…”

“…Effect sizes (Cohen's D ) were calculated from mean changes in variables (strength [ES = 1.65], hypertrophy [ES = 1.58], creatine kinase [ES = 3.95], ROM [ES = 1.78], tendon stiffness [ES = 1.10], elastic energy storage [ES = 1.88], and peak passive moment [ES = 2.11]) from previous studies employing similar interventions . To ensure adequate statistical power for all analyses, power analysis was conducted for tendon stiffness (ie, the variable with the smallest effect size) using the following parameters (variable = tendon stiffness, power = 0.80, alpha = 0.05, effect size = 1.1, attrition = 20%).…”

Reliability of Panoramic Ultrasound Imaging in Simultaneously Examining Muscle Size and Quality of the Hamstring Muscles in Young, Healthy Males and Females

“…Measurements of muscle quality, such as echo intensity (EI), are indicative of a muscle's fat and fibrous tissue content (Pillen et al 2009) and may also be potentially useful for assessing traininginduced increases in strength-related performances (Cadore et al 2014;Fukumoto et al 2013;Radaelli et al 2014). For example, Cadore et al (2014) recently reported that increases in maximal torque production after 6 wk of isokinetic training were significantly related to improvements in EI, which suggests that training-induced increases in muscle quality are linked to improvements in maximal strength. In light of these findings and given the potential contribution of CSA, MT and EI to measures of maximal and explosive strength and other functionally important parameters, recent research studies have heavily focused on identifying highly sensitive and reliable non-invasive imaging techniques for assessing muscle size and quality measurements (Caresio et al 2014;Melvin et al 2014;Rosenberg et al 2014;Strandberg et al 2010).…”

“…As a result, it has been suggested that muscle size measurements, such as cross-sectional area (CSA) and muscle thickness (MT), may be used as an indirect method to predict changes in maximal and/or explosive strength (Cormie et al 2010). Measurements of muscle quality, such as echo intensity (EI), are indicative of a muscle's fat and fibrous tissue content (Pillen et al 2009) and may also be potentially useful for assessing traininginduced increases in strength-related performances (Cadore et al 2014;Fukumoto et al 2013;Radaelli et al 2014). For example, Cadore et al (2014) recently reported that increases in maximal torque production after 6 wk of isokinetic training were significantly related to improvements in EI, which suggests that training-induced increases in muscle quality are linked to improvements in maximal strength.…”

Effect of two types of muscle contraction training on muscle thickness, strength, and delayed onset of muscle soreness in persons with chronic stroke

“…This result is different from those of previous studies. Cadore et al [36] reported a similar increase after 6 weeks of ECT and CCT in the VL MT of twenty-two healthy adults. In the study by Norrbrand et al [37], 15 healthy adults performed ECT and CCT for 5 weeks and MT increases of the quadriceps in the ECT group was reported, though the increase was not significant.…”