Muscle fibre types of the lumbrical, interossei, flexor, and extensor muscles moving the index finger

Abstract

The aim of this study was to determine the fibre types of the muscles moving the index fingers in humans. Fifteen forearms of eight adult cadavers were used. The sampled muscles were the first lumbrical (LM), first volar interosseous (VI), first dorsal interosseus (DI), second flexor digitorum profundus (FDP), second flexor digitorum superficialis (FDS), and extensor digitorum (ED). Six micrometer thick sections were stained for fast muscle fibres. The procedure was performed by applying mouse monoclonal anti-skeletal myosin antibody (fast) and avidin-biotin peroxidase complex staining. Rectangular areas (0.38 mm × 0.38 mm) were photographed and the boundaries of the muscle areas were marked on the translucent film. The numbers and sizes of the muscle fibres in each part were evaluated by the image analyser program and calculated per unit area (1 mm(2)). The proportion of the fast fibres was significantly (p = 0.012) greater in the intrinsic muscles (55.7 ± 17.1%) than in the extrinsic muscles (45.9 ± 17.1%). Among the six muscles, the VI had a significantly higher portion (59.3%) of fast fibres than the FDS (40.6%) (p = 0.005) or the FDP (45.1%) (p = 0.023). The density of the non-fast fibres was significantly (p = 0.015) greater in the extrinsic muscles (539.2 ± 336.8/mm(2)) than in the intrinsic muscles (383.4 ± 230.4/mm2). Since the non-fast fibres represent less fatigable fibres, it is thought that the extrinsic muscles have higher durability against fatigue, and the intrinsic muscles, including the LM, should move faster than the FDS or FDP because the MP joint should be flexed before the IP joint to grip an object.

Influence of blood flow occlusion on muscular recruitment and fatigue during maximal‐effort small muscle‐mass exercise

“…2005; Hwang et al . 2013) may result in differences in EMG‐sampled fibre‐type and explain discrepancies between the muscle activation patterns of the thigh (Burnley, 2009) and the forearm (this study). Lastly, although this study did not characterize fibre type, variability among subjects in recruitment patterns and the significant association between changes in RMS and TF pot (Fig.…”

Altered phalanx force direction during power grip following stroke

“…In addition, the distal intrinsic muscles may require more corticospinal drive than more proximal muscles (Palmer and Ashby 1992; Turton and Lemon 1999), leaving them more vulnerable to reduced neural activation post-stroke. Furthermore, intrinsic muscles may suffer from disproportionately greater underactivation due to changes occurring within the muscles: intrinsic muscles are composed predominantly of Type II muscle fibers (Hwang et al 2013), which have been shown to be particularly prone to atrophy post stroke (Dattola et al 1993; Hu et al 2007). …”

The effects of hypoxia on muscle deoxygenation and recruitment in the flexor digitorum superficialis during submaximal intermittent handgrip exercise

“…Performances of high intensity exercise can activate anaerobic glycolytic pathways for up to three minutes [47], a length of time similar to task duration in this study. This dependence on anaerbiosis may have been facilitated by the relatively high proportion of type II fibres in the FDS (41%) [48], which is much higher that the 20% reported in the adductor pollicis [49]. The exercise protocols in previous reports likely had greater involvement of aerobic pathways based on the fiber type proportion of the adductor pollicis [49], work to rest ratios (5 s on, 5 s off), and longer task durations [8,9,18].…”