Resistance-training-induced adaptations in skeletal muscle protein turnover in the fed state

Resistance training changes the balance of muscle protein turnover, leading to gains in muscle mass. A longitudinal design was employed to assess the effect that resistance training had on muscle protein turnover in the fed state. A secondary goal was investigation of the potential interactive effects of creatine (Cr) monohydrate supple mentation on resistance-training-induced adaptations. Young (N = 19, 23.7 ± 3.2 year), untrained (UT), healthy male subjects completed an 8-week resistance-training program (6 d/week). Supplementation with Cr had no impact on any of the variables studied; hence, all subsequent data were pooled. In the UT and trained (T) state, subjects performed an acute bout of resistance exercise with a single leg (exercised, EX), while their contralateral leg acted as a nonexercised (NE) control. Following exercise, subjects were fed while receiving a primed constant infusion of [d5]- and [15N]-phenylalanine to determine the fractional synthetic and breakdown rates (FSR and FBR), respectively, of skeletal muscle proteins. Acute exercise increased FSR (UT-NE, 0.065 ± 0.025 %/h; UT-EX, 0.088 ± 0.032 %/h; P < 0.01) and FBR (UT-NE, 0.047 ± 0.023 %/h; UT-EX, 0.058 ± 0.026 %/h; P < 0.05). Net balance (BAL = FSR FBR) was positive in both legs (P < 0.05) but was significantly greater (+65%) in the EX versus the NE leg (P < 0.05). Muscle protein FSR and FBR were greater at rest following T (FSR for T-NE vs. UT-NE, +46%, P < 0.01; FBR for T-NE vs. UT-NE, +81%, P < 0.05). Resistance training attenuated the acute exercise-induced rise in FSR (T-NE vs. T-EX, +20%, P = 0.65). The present results demonstrate that resistance training resulted in an elevated resting muscle protein turnover but an attenuation of the acute response of muscle protein turnover to a single bout of resistance exercise.Key words: myofibrillar protein, hypertrophy, protein synthesis, protein breakdown.

Download Full-text

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2000.278.3.r705 ◽

2000 ◽

Vol 278 (3) ◽

pp. R705-R711 ◽

Cited By ~ 8

Author(s):

T. A. McAllister ◽

J. R. Thompson ◽

S. E. Samuels

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Cardiac Muscle ◽

Cold Acclimation ◽

Protein Turnover ◽

Muscle Protein ◽

Muscle Protein Turnover ◽

Protein Mass ◽

The Absolute

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C (cold) or 25°C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was ∼28% lower in skeletal muscle (gastrocnemius and soleus) and ∼24% higher in heart in cold compared with control rats ( P < 0.05). In skeletal muscle, the fractional rates of protein synthesis ( k syn) and degradation ( k deg) were not significantly different between cold and control rats, although k syn was lower (approximately −26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately −21%; P < 0.05) and degradation (approximately −13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k syn(approximately +12%; P < 0.1) and k deg(approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats ( P < 0.05). Plasma triiodothyronine concentration was higher ( P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

Download Full-text

Resistance training reduces the acute exercise-induced increase in muscle protein turnover

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1999.276.1.e118 ◽

1999 ◽

Vol 276 (1) ◽

pp. E118-E124 ◽

Cited By ~ 67

Author(s):

S. M. Phillips ◽

K. D. Tipton ◽

A. A. Ferrando ◽

R. R. Wolfe

Keyword(s):

Resistance Training ◽

Resistance Exercise ◽

Acute Exercise ◽

Muscle Protein ◽

Exercise Bout ◽

Muscle Contractions ◽

Breakdown Rates ◽

Single Bout ◽

Fractional Synthesis ◽

Exercise Induced

We examined the effect of resistance training on the response of mixed muscle protein fractional synthesis (FSR) and breakdown rates (FBR) by use of primed constant infusions of [2H5]phenylalanine and [15N]phenylalanine, respectively, to an isolated bout of pleiometric resistance exercise. Trained subjects, who were performing regular resistance exercise (trained, T; n = 6), were compared with sedentary, untrained controls (untrained, UT; n = 6). The exercise test consisted of 10 sets (8 repetitions per set) of single-leg knee flexion (i.e., pleiometric muscle contraction during lowering) at 120% of the subjects’ predetermined single-leg 1 repetition maximum. Subjects exercised one leg while their contralateral leg acted as a nonexercised (resting) control. Exercise resulted in an increase, above resting, in mixed muscle FSR in both groups (UT: rest, 0.036 ± 0.002; exercise, 0.0802 ± 0.01; T: rest, 0.045 ± 0.004; exercise, 0.067 ± 0.01; all values in %/h; P< 0.01). In addition, exercise resulted in an increase in mixed muscle FBR of 37 ± 5% (rest, 0.076 ± 0.005; exercise, 0.105 ± 0.01; all values in %/h; P < 0.01) in the UT group but did not significantly affect FBR in the T group. The resulting muscle net balance (FSR − FBR) was negative throughout the protocol ( P < 0.05) but was increased in the exercised leg in both groups ( P < 0.05). We conclude that pleiometric muscle contractions induce an increase in mixed muscle protein synthetic rate within 4 h of completion of an exercise bout but that resistance training attenuates this increase. A single bout of pleiometric muscle contractions also increased the FBR of mixed muscle protein in UT but not in T subjects.

Download Full-text

Human muscle protein synthesis and breakdown during and after exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.91481.2008 ◽

2009 ◽

Vol 106 (6) ◽

pp. 2026-2039 ◽

Cited By ~ 148

Author(s):

Vinod Kumar ◽

Philip Atherton ◽

Kenneth Smith ◽

Michael J. Rennie

Keyword(s):

Protein Synthesis ◽

Amino Acid ◽

Protein Turnover ◽

Acute Exercise ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Mitochondrial Protein ◽

Human Muscle ◽

Muscle Protein Turnover ◽

Amino Acid Availability

Skeletal muscle demonstrates extraordinary mutability in its responses to exercise of different modes, intensity, and duration, which must involve alterations of muscle protein turnover, both acutely and chronically. Here, we bring together information on the alterations in the rates of synthesis and degradation of human muscle protein by different types of exercise and the influences of nutrition, age, and sexual dimorphism. Where possible, we summarize the likely changes in activity of signaling proteins associated with control of protein turnover. Exercise of both the resistance and nonresistance types appears to depress muscle protein synthesis (MPS), whereas muscle protein breakdown (MPB) probably remains unchanged during exercise. However, both MPS and MPB are elevated after exercise in the fasted state, when net muscle protein balance remains negative. Positive net balance is achieved only when amino acid availability is increased, thereby raising MPS markedly. However, postexercise-increased amino acid availability is less important for inhibiting MPB than insulin, the secretion of which is stimulated most by glucose availability, without itself stimulating MPS. Exercise training appears to increase basal muscle protein turnover, with differential responses of the myofibrillar and mitochondrial protein fractions to acute exercise in the trained state. Aging reduces the responses of myofibrillar protein and anabolic signaling to resistance exercise. There appear to be few, if any, differences in the response of young women and young men to acute exercise, although there are indications that, in older women, the responses may be blunted more than in older men.

Download Full-text