The Effects of Eccentric Training on Biceps Femoris Architecture and Strength: A Systematic Review With Meta-Analysis

Abstract

Objective: To determine the effects of an eccentric hamstrings strength-training program, performed for at least 4 weeks by healthy adults, on muscle architecture and eccentric strength.

Data sources: A systematic search was performed up to October 2018 in the following electronic databases: PubMed, PEDro, CINAHL and SPORTDiscus. Combinations of the following search terms were used: eccentric strength training, eccentric loading, nordic hamstring, hamstring strength, fascicle length, pennation angle, muscle thickness, muscle architecture, biceps femoris long head, biceps femoris, and hamstring muscles.

Study selection: Included articles were randomized controlled trials that allowed comparisons between isolated eccentric strength training of the biceps femoris muscle and other programs.

Data extraction: Data from the included studies were extracted by 2 independent reviewers. These data included the study design, participant characteristics, inclusion and exclusion criteria of clinical studies, exercise and intervention characteristics, outcome measures, and the main results of the study. When meta-analysis was possible, we performed quantitative analysis. Ten randomized controlled trials were included.

Data synthesis: Limited to moderate evidence indicated that eccentric strength training was associated with an increase in fascicle length (mean difference [MD] = 1.97; 95% confidence interval [CI] = 1.48, 2.46), an increase in muscle thickness (MD = 0.10; 95% CI = 0.06, 0.13), and a decrease in pennation angle (MD = 2.36; 95% CI = 1.61, 3.11). Conflicted to moderate evidence indicated that eccentric hamstrings strength was increased after eccentric strength training compared with concentric strength training (standardized mean difference [SMD] = 1.06; 95% CI = 0.26, 1.86), usual level of activity (SMD = 2.72; 95% CI = 1.68, 3.77), and static stretching (SMD = 0.39; 95% CI = -0.97, 1.75).

Conclusions: In healthy adults, an eccentric strength-training program produced architectural adaptations on the long head of the biceps femoris muscle and increased eccentric hamstrings strength.

Keywords: Nordic hamstrings; eccentric hamstrings strength; eccentric strength training; fascicle length; muscle architecture.

Figure 1

Flow chart of the study-selection process.

Figure 2

Authors' judgments about each risk-of-bias item presented as percentages across all included studies.

Figure 3

Forest plot of the difference in fascicle length between eccentric strength-training and control groups. Abbreviations: CI, confidence interval; Con, concentric; Ecc, eccentric; HEE, hip-extension exercise; MVIC, maximal voluntary isometric contraction; NA, no activity; NHE, Nordic hamstrings exercise; SS, static stretching; ULA, usual level of activity.

Figure 4

Forest plot of the difference in pennation angle between eccentric strength-training and control groups. Abbreviations: CI, confidence interval; Con, concentric; Ecc, eccentric; MVIC, maximal voluntary isometric contraction; NA, no activity; SS, static stretching.

Figure 5

Forest plot of the difference in muscle thickness between eccentric strength-training and control groups. Abbreviations: CI, confidence interval; Con, concentric; Ecc, eccentric; MVIC, maximal voluntary isometric contraction; NA, no activity.

Figure 6

Forest plot of the difference in eccentric hamstrings strength between eccentric strength-training and concentric strength-training (control) groups. Abbreviations: CI, confidence interval; Ecc, eccentric; Ham, hamstrings; PT, peak torque; RM, repetition maximum.

Figure 7

Forest plot of the difference in eccentric hamstrings strength between eccentric strength-training and usual-level-of-activity (control) groups. Abbreviations: CI, confidence interval; DOM, dominant; Ecc, eccentric; H : Q, eccentric hamstrings peak torque to concentric quadriceps peak torque; Ham, hamstrings; HEE, hip-extension exercise; Max, maximal; NDOM, nondominant; NHE, Nordic hamstrings exercise; PT, peak torque; RM, repetition maximum.

Figure 8

Forest plot of the difference in eccentric hamstrings strength between eccentric strength-training and static-stretching training (control) groups. Abbreviations: CI, confidence interval; Ecc, eccentric; H : Q, eccentric hamstrings peak torque to concentric quadriceps peak torque; Ham, hamstrings; PT, peak torque.