Downhill treadmill running trains the rat spinotrapezius muscle

Abstract

There are currently no models of exercise that recruit and train muscles, such as the rat spinotrapezius, that are suitable for transmission intravital microscopic investigation of the microcirculation. Recent experimental evidence supports the concept that running downhill on a motorized treadmill recruits the spinotrapezius muscle of the rat. Based on these results, we tested the hypothesis that 6 wk of downhill running (-14 degrees grade) for 1 h/day, 5 days/wk, at a speed of up to 35 m/min, would 1) increase whole body peak oxygen uptake (Vo(2 peak)), 2) increase spinotrapezius citrate synthase activity, and 3) reduce the fatigability of the spinotrapezius during electrically induced 1-Hz submaximal tetanic contractions. Trained rats (n = 6) elicited a 24% higher Vo(2 peak) (in ml.min(-1).kg(-1): sedentary 58.5 +/- 2.0, trained 72.7 +/- 2.0; P < 0.001) and a 41% greater spinotrapezius citrate synthase activity (in mumol.min(-1).g(-1): sedentary 14.1 +/- 0.7, trained 19.9 +/- 0.9; P < 0.001) compared with sedentary controls (n = 6). In addition, at the end of 15 min of electrical stimulation, trained rats sustained a greater percentage of the initial tension than their sedentary counterparts (control 34.3 +/- 3.1%, trained 59.0 +/- 7.2%; P < 0.05). These results demonstrate that downhill running is successful in promoting training adaptations in the spinotrapezius muscle, including increased oxidative capacity and resistance to fatigue. Since the spinotrapezius muscle is commonly used in studies using intravital microscopy to examine microcirculatory function at rest and during contractions, our results suggest that downhill running is an effective training paradigm that can be used to investigate the mechanisms for improved microcirculatory function following exercise training in health and disease.

Α‐adrenoceptor‐mediated Vasoconstriction Is Not Involved in Impaired Functional Vasodilation in the Obese Zucker Rat

“…Indeed, there is considerable vascular heterogeneity between muscles of the arms and legs in humans 35 . The spinotrapezius m. is a mixed‐fibre (41% type I, 7% type IIa and 17% type IIB) skeletal muscle involved in stabilizing the scapula and is recruited during downhill running 36 . Although we cannot exclude the possibility that adrenergic activity to other skeletal muscle beds differs from that of the spinotrapezius muscle, the spinotrapezius is a flat muscle of mixed fibre composition involved in both postural control and locomotion.…”

Exercise‐Induced Muscle Damage and Running Economy in Humans

“…Some studies have shown that downhill running can lead to muscle damage of the same magnitude as plyometric or maximal eccentric exercises [92, 98]. Considering that downhill running induces muscle damage, a series of studies have investigated its influence on neuromuscular and metabolic markers in animals [99] and humans [11, 93, 94, 98]. In animals, downhill running has been utilised to induce overtraining [100] as well as a training method to increase the number of sarcomeres [101].…”

Efeitos da caminhada em declive na aptidão aeróbia e neuromuscular em adultos jovens

“…Based on evidences obtained in animal models 18,19 , we hypothesized that DW could represent an additional stress in relation to walking level, considering the oxidative adaptations provided by downhill walking and running 18,19 , to improve aerobic power. Hahn and colleagues 18 identified an increase in the total content of citrate synthase enzyme, a key regulatory enzyme in assessing oxidative capacity, after 6 weeks of downhill running training in mice. There is also evidence pointing to acutely increased vascularization and oxygenation of the muscle tissue of mice after a single bout of DW 19 .…”

“…Similarly, Gault & Willems 16 showed that IPT and torque steadiness were also improved after 12 weeks of DW training in older individuals. Interestingly, Hahn et al 18 found significant increases in the total content of citrate synthase enzyme after 6 weeks of downhill running training in mice, while Ahmadi et al 19 reported acute increases in vascularization and muscle oxygenation after a DW session in mice. These data, associated with the classical finding of Saltinet al 20 and Wagner 21 , which showed that peripheral adaptations play an important role in increasing aerobic power, indicate that DW training could improve aerobic fitness.…”