Effects Of Thermotherapy And Cryotherapy On Muscle Hypertrophy And Muscle Contraction Force Following Resistance Exercise

This study compared the effects of the most frequently employed protocols of flywheel (FW) versus weight-stack (WS) resistance exercise (RE) on regional and muscle-specific adaptations of the knee extensors. Sixteen men (n = 8) and women (n = 8) performed 8 weeks (2–3 days/week) of knee extension RE employing FW technology on 1 leg (4 × 7 repetitions), while the contralateral leg performed regular WS training (4 × 8–12 repetitions). Maximal strength (1-repetition maximum (1RM) in WS) and peak FW power were determined before and after training for both legs. Partial muscle volume of vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), and rectus femoris (RF) were measured using magnetic resonance imaging. Additionally, quadriceps cross-sectional area was assessed at a proximal and a distal site. There were no differences (P > 0.05) between FW versus WS in muscle hypertrophy of the quadriceps femoris (8% vs. 9%), VL (10% vs. 11%), VM (6% vs. 8%), VI (5% vs. 5%), or RF (17% vs. 17%). Muscle hypertrophy tended (P = 0.09) to be greater at the distal compared with the proximal site, but there was no interaction with exercise method. Increases in 1RM and FW peak power were similar across legs, yet the increase in 1RM was greater in men (31%) than in women (20%). These findings suggest that FW and WS training induces comparable muscle-specific hypertrophy of the knee extensors. Given that these robust muscular adaptations were brought about with markedly fewer repetitions in the FW compared with WS, it seems FW training can be recommended as a particularly time-efficient exercise paradigm.

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Exercise May Promote Skeletal Muscle Hypertrophy via Enhancing Leucine-Sensing: Preliminary Evidence

Frontiers in Physiology ◽

10.3389/fphys.2021.741038 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yan Zhao ◽

Jason Cholewa ◽

Huayu Shang ◽

Yueqin Yang ◽

Xiaomin Ding ◽

...

Keyword(s):

Protein Synthesis ◽

Resistance Exercise ◽

Aerobic Exercise ◽

Protein Concentration ◽

Muscle Hypertrophy ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Muscle Fibers ◽

Mtor Signaling ◽

Treadmill Running

Several studies have indicated a positive effect of exercise (especially resistance exercise) on the mTOR signaling that control muscle protein synthesis and muscle remodeling. However, the relationship between exercise, mTOR activation and leucine-sensing requires further clarification. Two month old Sprague-Dawley rats were subjected to aerobic exercise (treadmill running at 20 m/min, 6° incline for 60 min) and resistance exercise (incremental ladder climbing) for 4 weeks. The gastrocnemius muscles were removed for determination of muscle fibers diameter, cross-sectional area (CSA), protein concentration and proteins involved in muscle leucine-sensing and protein synthesis. The results show that 4 weeks of resistance exercise increased the diameter and CSA of gastrocnemius muscle fibers, protein concentration, the phosphorylation of mTOR (Ser2448), 4E-BP1(Thr37/46), p70S6K (Thr389), and the expression of LeuRS, while aerobic exercise just led to a significant increase in protein concentration and the phosphorylation of 4E-BP1(Thr37/46). Moreover, no difference was found for Sestrin2 expression between groups. The current study shows resistance exercise, but not aerobic exercise, may increase muscle protein synthesis and protein deposition, and induces muscle hypertrophy through LeuRS/mTOR signaling pathway. However, further studies are still warranted to clarify the exact effects of vary intensities and durations of aerobic exercise training.

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Tubular Repair of the Median Nerve in the Human Forearm

Journal of Hand Surgery (European Volume) ◽

10.1016/0266-7681(94)90068-x ◽

1994 ◽

Vol 19 (3) ◽

pp. 273-276 ◽

Cited By ~ 91

Author(s):

G. LUNDBORG ◽

B. ROSÉN ◽

S. O. ABRAHAMSON ◽

L. DAHLIN ◽

N. DANIELSEN

Keyword(s):

Muscle Contraction ◽

Median Nerve ◽

Hand Function ◽

Nerve Trunk ◽

Contraction Force ◽

Silicone Tube ◽

Human Forearm ◽

Normal Hand ◽

Male Patients ◽

Chamber Technique

Transected median nerves in the forearm of two male patients, 12 and 21 years of age, were treated with a chamber technique leaving a 3 to 5 mm gap between the nerve ends. The nerve ends were enclosed in a silicone tube of such a dimension that would not cause compression of the nerve. Post-operative examination including sensory evaluation and assessment of muscle contraction force was carried out after 3 years. In both cases there was excellent motor recovery of the thenar muscles. Outgrowth of sensory fibres was remarkably fast, resulting ultimately in functional sensibility allowing almost normal hand function. 2PD was ⩽ 6 mm (12year-old patient) and 8 to 10 mm (21-year-old patient) respectively. In one case the silicone tube was re-explored because of minor local discomfort 2 years after the repair. The former gap was bridged by a smooth continuous nerve-like structure of the same diameter as the adjacent nerve trunk and with no signs of nenroma formation or compression of the nerve.

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Stimuli and sensors that initiate skeletal muscle hypertrophy following resistance exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00685.2018 ◽

2019 ◽

Vol 126 (1) ◽

pp. 30-43 ◽

Cited By ~ 45

Author(s):

Henning Wackerhage ◽

Brad J. Schoenfeld ◽

D. Lee Hamilton ◽

Maarit Lehti ◽

Juha J. Hulmi

Keyword(s):

Skeletal Muscle ◽

Resistance Exercise ◽

Muscle Damage ◽

Muscle Hypertrophy ◽

Muscle Protein ◽

Large Body ◽

Focal Adhesions ◽

Indirect Evidence ◽

Skeletal Muscle Hypertrophy ◽

Exercise Induced

One of the most striking adaptations to exercise is the skeletal muscle hypertrophy that occurs in response to resistance exercise. A large body of work shows that a mammalian target of rapamycin complex 1 (mTORC1)-mediated increase of muscle protein synthesis is the key, but not sole, mechanism by which resistance exercise causes muscle hypertrophy. While much of the hypertrophy signaling cascade has been identified, the initiating, resistance exercise-induced and hypertrophy-stimulating stimuli have remained elusive. For the purpose of this review, we define an initiating, resistance exercise-induced and hypertrophy-stimulating signal as “hypertrophy stimulus,” and the sensor of such a signal as “hypertrophy sensor.” In this review we discuss our current knowledge of specific mechanical stimuli, damage/injury-associated and metabolic stress-associated triggers, as potential hypertrophy stimuli. Mechanical signals are the prime hypertrophy stimuli candidates, and a filamin-C-BAG3-dependent regulation of mTORC1, Hippo, and autophagy signaling is a plausible albeit still incompletely characterized hypertrophy sensor. Other candidate mechanosensing mechanisms are nuclear deformation-initiated signaling or several mechanisms related to costameres, which are the functional equivalents of focal adhesions in other cells. While exercise-induced muscle damage is probably not essential for hypertrophy, it is still unclear whether and how such muscle damage could augment a hypertrophic response. Interventions that combine blood flow restriction and especially low load resistance exercise suggest that resistance exercise-regulated metabolites could be hypertrophy stimuli, but this is based on indirect evidence and metabolite candidates are poorly characterized.

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