Site‐specific features of active muscle stiffness and proximal aponeurosis strain in biceps femoris long head

Abstract

Limited information is available on site‐specific features of muscle stiffness and aponeurosis strain of the biceps femoris long head (BFlh) during contractions. Therefore, understanding of the mechanics and etiology of hamstring strain injuries remains difficult. As a first step to gain further insight into them, the present study aimed to identify whether active muscle stiffness and proximal aponeurosis strain during contractions are varied along the long axis of the BFlh. The BFlh muscle shear wave speed (proxy for stiffness) was measured in the proximal, central, and distal sites during 20%, 50%, and 80% of maximal voluntary isometric contraction (MVC) of knee flexion exerted with the hip and knee joints flexed at 40° and 30°, respectively, using ultrasound shear wave elastography. Further, a segmental strain of the BFlh proximal aponeurosis was assessed in the proximal, central, and distal sites during isometric knee flexion, using B‐mode ultrasonography. The shear wave speed was significantly higher in the distal site than the proximal and central sites at 20% MVC (p ≤ .002, with a large effect size), whereas no significant difference was found between the three sites at 50% and 80% MVC. The BFlh proximal aponeurosis strain showed no significant difference between the proximal, central, and distal sites at any contraction intensity. These findings indicate that site‐specific differences in muscle stiffness and proximal aponeurosis strain are substantially small and that muscle stiffness and proximal aponeurosis strain of the BFlh at moderate‐to‐high contraction intensity is not exceptional in the site where a sprinting‐type hamstring strain typically occurs.

The structure, function, and adaptation of lower-limb aponeuroses: implications for myo-aponeurotic injury.

“…This is the case for the posterior aponeurosis of the soleus in which a 2.2% increase in length was recorded in the thinner mid region compared to a 2.5% decrease at the thicker distal region[148] during submaximal isometric conditions. Similar regional differences were also reported for the medial gastrocnemius, and BFlh during submaximal isometric contractions (10-40% MVIC) [141,157] as well as during passive lengthening in cadaveric specimens of the triceps surae [99]. Contrastingly, the BFlh proximal aponeurosis strain pattern was reversed as contraction intensity increased (40-70% MVIC) in which both the thicker proximal and distal regions appeared to strain more than the middle region.…”

“…At 90%-100% MVIC, longitudinal strain of the anterior aponeurosis of the medial gastrocnemius typically ranged from 4-7% [140,142,146], compared to 1-4% at 10%-30% MVIC [130,146]. This pattern of increasing longitudinal strain with increasing contraction intensities is also re ected in the central aponeurosis of tibialis anterior [133,136,150,153], deep aponeurosis of vastus lateralis [127] and the proximal aponeurosis of BFlh [157] (Table 3). The longitudinal strain of the proximal aponeurosis of semitendinosus also increases with the contraction intensity while that of the distal aponeurosis decreases with increasing contraction intensity[156] (Table 3).…”

Hamstrings on Morphological Structure Characteristics, Stress Features, and Risk of Injuries: A Narrative Review

“…Sci. 2022, 12, 12713 2 of 13 these injuries appear in the biceps femoris long head (BFLH) [12][13][14][15][16]. For example, in 17 subjects with single injuries or isolated re-injuries, 12 of these were injured on the proximal part [17].…”

“…It has been reported that 57-72% of all hamstring injuries occur during sprinting. Nearly 94% of these injuries appear in the biceps femoris long head (BFLH) [12][13][14][15][16]. For example, in 17 subjects with single injuries or isolated re-injuries, 12 of these were injured on the proximal part [17].…”

Hamstring Activity Before and After Break-Point Angle Calculated By Smartphone Application During the Nordic Hamstring Exercise

“…[6][7][8] Notably, the reduction in BF EMG activity is particularly prominent at knee flexion angles of 15-35° (0° indicates a fully extended knee), [6][7][8] which align with the angles at which hamstring injuries commonly occur. 9,10 It has also been reported that isokinetic knee flexion training incorporating eccentric loading up to 20° knee flexion can effectively prevent recurrent hamstring injuries. 11 Therefore, the implementation of knee flexion exercises that enhance BF EMG activity at angles of 15-35° might play a crucial role in preventing the recurrence of hamstring injuries.…”