Increased oxidative capacity does not protect skeletal muscle fibers from eccentric contraction-induced injury

Abstract

Isometric electrical stimulation was delivered to rabbit dorsiflexor muscles at 10 Hz for 1 s on and 1 s off over 30 min, 5 days/wk for 3 wk to induce an increase in muscle oxidative capacity. Stimulation-trained muscles as well as untrained muscles were then subjected to a 30-min eccentric exercise bout to test whether increased oxidative capacity provided a protective effect against muscle injury. Electrical stimulation resulted in significant training of both the extensor digitorum longus (EDL) and tibialis anterior (TA) muscles, with EDL citrate synthase (CS) activity increasing an average of 67% ( P < 0.0001) and TA CS activity increasing by 27% ( P < 0.05). For all parameters measured, the magnitude of change was much greater for EDL than for TA muscle. Dorsiflexor fatigability decreased significantly during the 3-wk training period ( P < 0.0001), whereas the EDL and TA individually showed strong decreasing trends in fatigability after training. TA and EDL capillary density measured histomorphometrically increased from 839 ± 56 to 1,026 ± 71 mm−2( P = 0.07) and from 589 ± 37 to 792 ± 66 mm−2( P < 0.05), respectively. TA and EDL capillary-to-fiber ratio increased from 1.32 ± 0.10 to 1.55 ± 0.16 ( P > 0.2) and 1.08 ± 0.07 to 1.36 ± 0.14 ( P > 0.1), respectively. Type 2A fiber type percentage increased after stimulation training by 68% ( P < 0.0001) for the EDL and by 32% ( P > 0.1) for the TA at the expense of type 2D fibers. Despite the large training effect for the EDL and the modest training effect for the TA, no differences were observed between stimulation-trained and untrained groups for maximum dorsiflexion torque ( P > 0.3) or maximum tetanic tension ( P > 0.3) after eccentric contraction-induced injury. Additionally, no significant correlation was observed between CS activity and maximum tetanic tension after eccentric contraction-induced injury for either muscle ( P > 0.2). Thus we conclude that increasing muscle oxidative capacity by isometric electrical stimulation training did not protect muscle against eccentric contraction-induced injury.

Low-frequency fatigue is fibre type related and most pronounced after eccentric activity in rat medial gastrocnemius muscle

“…Evans et al [12] showed that endurance training of human muscle led to less damage following eccentric contractions while data from Patel et al [28] showed that, in rat muscles, increased oxidative capacity by electrical stimulation training did not result in less injury after eccentric exercise. Furthermore, Skurvydas et al [33] stated that endurance training and slow muscle fibre type prevalence does not result in less LFF, and neither does it accelerate the recovery of muscle contraction force following maximal, intermittent stretchshortening cycle exercise.…”

Dynamic force responses of skeletal muscle during stretch–shortening cycles

“…Studies using humans have demonstrated that repeated, intense, unaccustomed eccentric contractions result in myofibrillar ultrastructural disturbances immediately after the activity (Friden et al 1983;Newham et al 1983), delayed onset muscle soreness (Friden et al 1981;Newham et al 1987), and long-lasting muscle fatigue (Clarkson and Newham 1995). Animal studies utilizing dynamometry techniques have been used to investigate the effect of exposure to unaccustomed eccentric contractions on mice (Faulkner et al 1981;McCully and Faulkner 1986;Warren et al 1993Warren et al , 1996, rabbits (Lieber et al 1991(Lieber et al , 1996Koh and Herzog 1998;Patel et al 1998), and rats (Hesselink et al 1996;Komulainen et al 1998;Stauber 2000a, 2001). Studies using animals have shown that there is immediate post-exposure ultrastructural disorganization (Lieber et al 1991), myofiber necrosis 1-3 days after exposure (McCully and Faulkner 1986;Lowe et al 1995;Lieber et al 1996;Hesselink et al 1996;Komulainen et al 1998), and a long-lasting force decrement (Ingalls et al 1998).…”

Modulation of trophism and fiber type gene expression in denervated muscle activated by different patterns of electrical stimulation. Role of muscle fiber regeneration revisited in 2017

“…[93,94]. In denervated muscles the results mimic the well-known efficacy of high frequency electrical stimulation to induce skeletal muscle hypertrophy [95], and of low frequency electrical stimulation protocol to induce endurancelike adaptations when applied 5 days/week for 3 weeks [81,96,97]. Recent evidence shows that trophism and fiber type are regulated independently through different transduction signaling pathways [98][99][100][101].…”