You're a bodybuilder, but you can only train with minimal weights because of an injury, and you're worried about your muscle mass. Is that your problem? Then sports scientists at the University of Copenhagen have good news for you. Even if you can only train with minimal weights that'll help you to retain some of your muscle mass, the Danes write in an article that will soon be published in Clinical Nutrition. At least, it will if you consume enough protein.
In 2008 the Danes made a discovery that strength athletes would probably react to by saying 'but we already knew that'. [J Appl Physiol. 2008 Nov; 105(5): 1454-61.] The researchers got their subjects to train their quads on a leg-extension machine for 12 weeks. The men trained their one leg with sets using 70 percent of their 1RM [Heavy] and the other with 16 percent of that weight [Light].
We copied the figure below from their study. It shows the circumference of the subjects' quads before and after the 12 weeks. The heavy training had more effect than the light training.
The heavy training resulted in a 7.5 percent increase in muscle circumference; the light a 2.5 percent increase. The latter figure intrigued the researchers. Apparently training with very light weights also helps muscles to grow. And that's of interest to people who want to retain muscle mass, but for one reason or another can’t train with heavy weights.
The researchers will soon publish the results of a study in which they examined the relationship between protein supplementation and light strength training. In this study the Danes used 10 males in their twenties as subjects. They got the men to train one leg on a leg-extension machine, using weights at 16 percent of their 1RM, early in the morning. For each exercise they did they did 10 sets of 36 reps. Between sets the men paused for 30 seconds. The other leg did nothing.
For ten hours after this lopsided workout the Danes monitored the production of muscle tissue in the men’s quadriceps. They were also given a small protein shake, at first every half hour and later once an hour. In total the subjects consumed about a dozen shakes, and a total of about 65 g protein.
The figure below shows that in the non-active the anabolic effect of the protein supplement disappeared after eight hours, but in the leg that was trained it was still present ten hours after the workout.
"It should be acknowledged that heavy load exercise is the most potent exercise-stimulus to increase muscle protein turnover and muscle accretion", the researchers write. "The phenomenon that resistance exercise-type light-load contractions is sufficient to improve the muscle sensitivity to protein feeding, may lend support for a muscle mass preserving effect. The results could be relevant for hospitalized or partly immobilized patients, who could be hypothesised to attenuate muscle atrophy by completing brief light-load contractile activity combined with protein-supplemented diets."
Changes in muscle size and MHC composition in response to resistance exercise with heavy and light loading intensity.
Holm L, Reitelseder S, Pedersen TG, Doessing S, Petersen SG, Flyvbjerg A, Andersen JL, Aagaard P, Kjaer M.
Institute of Sports Medicine, Bispebjerg Hospital, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark. firstname.lastname@example.org
Muscle mass accretion is accomplished by heavy-load resistance training. The effect of light-load resistance exercise has been far more sparsely investigated with regard to potential effect on muscle size and contractile strength. We applied a resistance exercise protocol in which the same individual trained one leg at 70% of one-repetition maximum (1RM) (heavy load, HL) while training the other leg at 15.5% 1RM (light load, LL). Eleven sedentary men (age 25 +/- 1 yr) trained for 12 wk at three times/week. Before and after the intervention muscle hypertrophy was determined by magnetic resonance imaging, muscle biopsies were obtained bilaterally from vastus lateralis for determination of myosin heavy chain (MHC) composition, and maximal muscle strength was assessed by 1RM testing and in an isokinetic dynamometer at 60 degrees /s. Quadriceps muscle cross-sectional area increased (P < 0.05) 8 +/- 1% and 3 +/- 1% in HL and LL legs, respectively, with a greater gain in HL than LL (P < 0.05). Likewise, 1RM strength increased (P < 0.001) in both legs (HL: 36 +/- 5%, LL: 19 +/- 2%), albeit more so with HL (P < 0.01). Isokinetic 60 degrees /s muscle strength improved by 13 +/- 5% (P < 0.05) in HL but remained unchanged in LL (4 +/- 5%, not significant). Finally, MHC IIX protein expression was decreased with HL but not LL, despite identical total workload in HL and LL. Our main finding was that LL resistance training was sufficient to induce a small but significant muscle hypertrophy in healthy young men. However, LL resistance training was inferior to HL training in evoking adaptive changes in muscle size and contractile strength and was insufficient to induce changes in MHC composition.
PMID: 18787090 [PubMed - indexed for MEDLINE]
The anabolic potential of dietary protein intake on skeletal muscle is prolonged by prior light-load exercise.
Bechshoeft R, Dideriksen KJ, Reitelseder S, Scheike T, Kjaer M, Holm L.
Institute of Sports Medicine, Dept. of Orthopedic Surgery M81, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
BACKGROUND & AIMS:
Hyperaminoacidemia stimulates myofibrillar fractional synthesis rate (myoFSR) transiently in resting skeletal muscle. We investigated whether light-load resistance exercise can extent this responsiveness.
Ten healthy males exercised one leg with a light-load resistance-like exercise at 16% of 1 repetition maximum and received oral protein boluses every hour for a 10-h period. Their myoFSR was determined by [1-(13)C]-leucine incorporation. Muscle biopsies were obtained from the resting (REST) and exercised (EXC) muscles every 2.5-h in the protein-fed period.
Protein feeding significantly elevated plasma leucine and essential amino acids by an average of 39 ± 9% (mean ± SEM) and 20 ± 4%, respectively, compared to the basal concentrations: 197 ± 12 μmol L(-1) and 854 ± 35 μmol L(-1), respectively. The myoFSR was similar in EXC and REST muscles in the first 8 h (all time intervals p > 0.05). After 8 h the myoFSR dropped in the REST muscle to 0.041 ± 0.005%·h(-1), which was 65 ± 5% of the rate in EXC leg at the same time point (0.062 ± 0.004%·h(-1)) and 80 ± 14% of the level in REST leg from 0.5 to 8 h (0.056 ± 0.005%·h(-1)) (interaction p < 0.05). CONCLUSIONS: Compared to rest, light-load exercise prolonged the stimulatory effect of dietary protein on muscle biosynthesis providing perspectives for a muscle restorative effect in clinical settings where strenuous activity is intolerable. Copyright © 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. PMID: 22867749 [PubMed - as supplied by publisher] Source: http://www.ncbi.nlm.nih.gov/pubmed/22867749