Hamstring Architectural and Functional Adaptations Following Long vs. Short Muscle Length Eccentric Training

Abstract

Most common preventive eccentric-based exercises, such as Nordic hamstring do not include any hip flexion. So, the elongation stress reached is lower than during the late swing phase of sprinting. The aim of this study was to assess the evolution of hamstring architectural (fascicle length and pennation angle) and functional (concentric and eccentric optimum angles and concentric and eccentric peak torques) parameters following a 3-week eccentric resistance program performed at long (LML) vs. short muscle length (SML). Both groups performed eight sessions of 3–5 × 8 slow maximal eccentric knee extensions on an isokinetic dynamometer: the SML group at 0° and the LML group at 80° of hip flexion. Architectural parameters were measured using ultrasound imaging and functional parameters using the isokinetic dynamometer. The fascicle length increased by 4.9% (p < 0.01, medium effect size) in the SML and by 9.3% (p < 0.001, large effect size) in the LML group. The pennation angle did not change (p = 0.83) in the SML and tended to decrease by 0.7° (p = 0.09, small effect size) in the LML group. The concentric optimum angle tended to decrease by 8.8° (p = 0.09, medium effect size) in the SML and by 17.3° (p < 0.01, large effect size) in the LML group. The eccentric optimum angle did not change (p = 0.19, small effect size) in the SML and tended to decrease by 10.7° (p = 0.06, medium effect size) in the LML group. The concentric peak torque did not change in the SML (p = 0.37) and the LML (p = 0.23) groups, whereas eccentric peak torque increased by 12.9% (p < 0.01, small effect size) and 17.9% (p < 0.001, small effect size) in the SML and the LML group, respectively. No group-by-time interaction was found for any parameters. A correlation was found between the training-induced change in fascicle length and the change in concentric optimum angle (r = −0.57, p < 0.01). These results suggest that performing eccentric exercises lead to several architectural and functional adaptations. However, further investigations are required to confirm the hypothesis that performing eccentric exercises at LML may lead to greater adaptations than a similar training performed at SML.

The effect of Nordic hamstring strength training on muscle architecture, stiffness, and strength

“…Thus, the joint positions during the NH curl training may have contributed to the lack of fascicle length change (and the lack of shift in maximal eccentric torque towards longer lengths) seen after the intervention. Additionally, when fascicle increases have been shown to occur, they increase fairly quickly; 3-5 weeks into eccentric training (Blazevich et al 2007;Baroni et al 2013;Guex et al 2016;Bourne et al 2016). The current NH intervention length of 6 weeks was similar to previous studies (Iga et al 2012;Delahunt et al 2016).…”

“…Sharifnezhad et al (2014) confirmed that fascicle length increases are dependent on the range of lengths used during the intervention; showing the vastus lateralis fascicle lengths increased in the leg that exercised at a longer muscle length (25-100° knee flexion), with no change in fascicle length for the leg exercised at a shorter muscle length (25-65° knee flexion) after training. Further, Guex et al (2016) confirmed that hamstring fascicle length increases after a dynamometer-based eccentric strength intervention are dependent on the muscle length during training; BFLH fascicle lengths increased more when trained at a longer muscle length (80° hip flexion), compared to shorter muscle length (0° hip flexion). Thus, the joint positions during the NH curl training may have contributed to the lack of fascicle length change (and the lack of shift in maximal eccentric torque towards longer lengths) seen after the intervention.…”

Skeletal Muscle Remodeling in Response to Eccentric vs. Concentric Loading: Morphological, Molecular, and Metabolic Adaptations

“…This hypothesis seems supported by other studies (McMahon et al, 2014; Guex et al, 2016), which found a greater increase in fascicle length of VL when training at greater ROM of the knee joint. Nonetheless, Noorkõiv et al (2014) showed that isometric training at longer muscle lengths (i.e., thus almost re-producing an ECC contraction scenario) can induce a substantial increase in Lf.…”

Isometric training and long‐term adaptations: Effects of muscle length, intensity, and intent: A systematic review

“…All three studies found that isometric training at long muscle lengths (LMLs) was superior to equal volumes of training at short muscle lengths (SMLs) for increasing muscle size . These findings are not surprising as a large portion of the existing literature has demonstrated that dynamic training through a large range of motion is beneficial when hypertrophy is desired . Additionally, contractions at LML tend to produce higher quantities of muscle damage, likely by altering the joint moment arm and increasing mechanical tension when compared to a SML .…”