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The Effects of Aerobic Exercise on Human Skeletal Muscle Adaptations to Resistance Exercise
Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Aerobic exercise (AE) may interfere with muscle adaptations induced by resistance exercise (RE). Three experimental campaigns were conducted to explore the influence of AE on molecular, functional and muscular adaptations to acute and chronic RE. Twenty-nine men performed unilateral knee extensor RE preceded by AE (AE+RE). The contralateral leg did RE only. First, the influence of acute AE on muscle molecular responses to RE performed 6 h later was studied. Subsequently, this exercise regimen was implemented over 5 weeks training. The relationships between acute and chronic outcomes were examined and molecular responses to acute exercise were assessed in untrained and trained muscle. Finally, acute and chronic responses to AE+RE, interspersed by only 15 min recovery, were investigated.Phosphorylation of mTOR and p70S6K was greater after AE+RE than after RE. In parallel, myostatin was suppressed for a longer time after AE+RE. These results suggest that AE+RE enhance skeletal muscle anabolic environment more than RE alone (Paper I). After 5 weeks training, improvements in muscle strength and power were similar across legs. However, AE+RE prompted a greater increase in muscle size than RE, suggesting that AE potentiates the hypertrophic stimulus to RE training without altering muscle function progress (Paper II). Consistent with changes in whole-muscle size, AE+RE showed greater anabolic molecular responses than RE. As chronic training blunted this effect, it appears that AE offers a synergistic hypertrophic stimulus to RE only during short-term training (Paper III). Although putative regulators of hypertrophy such as p70S6K, myostatin and PGC-1a4 were examined, no molecular marker correlated with changes in muscle size, strength or power induced by training. Hence, this study challenges the concept that single molecular markers are viable predictors of training-induced muscle adaptations (Paper III–IV). When recovery time between exercise bouts was reduced to 15 min, AE+RE still produced a more substantial increase in muscle size than RE. However, progression of concentric strength was blunted. Thus, while restored muscle function between exercise bouts is a prerequisite for achieving maximal gains in strength and power, incomplete recovery appears not to compromise muscle hypertrophy (Paper V).Collectively, the results suggest that outcomes of AE+RE are impacted by chronic training and time allowed for recovery between exercise modes. Yet, the current study offers no support to the view that AE interferes with muscle hypertrophy induced by RE.

Place, publisher, year, edition, pages
Östersund: Mittuniversitetet , 2014. , 73 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 181
Keyword [en]
concurrent training, endurance, gene expression, hypertrophy, muscle strength and power, protein phosphorylation
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:miun:diva-21917ISBN: 978-91-87557-41-5 (print)OAI: oai:DiVA.org:miun-21917DiVA: diva2:716115
Public defence
2014-05-15, F229, Östersund, 13:00 (English)
Opponent
Supervisors
Available from: 2014-05-08 Created: 2014-05-08 Last updated: 2014-05-09Bibliographically approved
List of papers
1. Aerobic Exercise Alters Skeletal Muscle Molecular Responses to Resistance Exercise
Open this publication in new window or tab >>Aerobic Exercise Alters Skeletal Muscle Molecular Responses to Resistance Exercise
2012 (English)In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 44, no 9, 1680-1688 p.Article in journal (Refereed) Published
Abstract [en]

LUNDBERG, T. R., R. FERNANDEZ-GONZALO, T. GUSTAFSSON, and P. A. TESCH. Aerobic Exercise Alters Skeletal Muscle Molecular Responses to Resistance Exercise. Med. Sci. Sports Exerc., Vol. 44, No. 9, pp. 1680-1688, 2012. Purpose: This study assessed the influence of an acute aerobic exercise bout on molecular responses to subsequent resistance exercise (RE). Methods: Nine physically active men performed a 45-min one-legged cycle ergometry exercise and 4 x 7 maximal concentric eccentric knee extensions for each leg 6 h later. Thus, one limb was subjected to aerobic and resistance exercise (AE+RE), and the contralateral limb to resistance exercise (RE) only. Knee extensor peak power was determined. Biopsies were obtained from the m vastus lateralis before (PRE) and 15 mm (POST1) and 3 h after RE. Analysis determined glycogen content, mRNA levels (vascular endothelial growth factor, peroxisome proliferator activated receptor-gamma coactivator-1, muscle RING-finger protein-1, atrogin-1, myostatin), and phosphorylated proteins (mammalian target of rapamycin, p70S6 kinase, ribosomal protein S6, eukaryotic elongation factor 2). Results: Peak power was similar in AE + RE and RE. After RE, the time course of glycogen utilization and protein signaling was similar across legs. However, phosphorylation of mammalian target of rapamycin and p70S6 kinase was elevated in AE + RE versus RE (main effect, P < 0.05). Vascular endothelial growth factor and peroxisome proliferator activated receptor-gamma coactivator-1 were higher in AE + RE than in RE at PRE and POST1 (P < 0.05). Myostatin was lower in AE + RE versus RE at PRE and POST1 (P < 0.05) and downregulated after resistance exercise only. Atrogin-1 was higher in AE + RE than in RE at PRE and POST1 (P < 0.05) and decreased after RE in AE + RE. Muscle RING-finger protein-1 was similar across legs. No difference for any marker was evident 3 h after RE. Conclusions: These results suggest that acute aerobic exercise alters molecular events regulating muscle protein turnover during the early recovery period from subsequent RE.

Keyword
ENDURANCE, HUMAN SKELETAL MUSCLE, mTOR, MUSCLE POWER, PGC-1 alpha, P70S6K
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-17251 (URN)10.1249/MSS.0b013e318256fbe8 (DOI)000307624600008 ()2-s2.0-84865529379 (Scopus ID)
Available from: 2012-10-29 Created: 2012-10-27 Last updated: 2017-12-07Bibliographically approved
2. Aerobic exercise does not compromise muscle hypertrophy response to short-term resistance training
Open this publication in new window or tab >>Aerobic exercise does not compromise muscle hypertrophy response to short-term resistance training
2013 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 114, no 1, 81-89 p.Article in journal (Refereed) Published
Abstract [en]

This study tested the hypothesis that chronic aerobic and resistance exercise (AE+RE) would elicit greater muscle hypertrophy than resistance exercise only (RE). Ten men (25±4 yrs) performed 5 wks unilateral knee extensor AE+RE. The opposing limb was subjected to RE. AE completed 6 hrs prior to RE, consisted of ~45 min one-legged cycle ergometry. RE comprised 4 x 7 maximal concentric-eccentric knee extensions. Various indices of in vivo knee extensor function were measured before and after training. Magnetic resonance imaging (MRI) assessed m. quadricep femoris (QF) cross-sectional area (CSA), volume, and signal intensity (SI). Biopsies obtained from m. vastus lateralis determined fiber CSA, enzyme levels and gene expression of myostatin, atrogin-1, MuRF-1, PGC-1α and VEGF. Increases (P < 0.05) in isometric strength and peak power, respectively were comparable in AE+RE (9 and 29%) and RE (11 and 24%). AE+RE showed greater increase (14%; P < 0.05) in QF volume than RE (8%). Muscle fiber CSA increased 17% after AE+RE (P < 0.05) and 9% after RE (P > 0.05). QF SI increased (12%; P < 0.05) after AE+RE, but not RE. Neither AE+RE nor RE showed altered mRNA-levels. Citrate Synthase activity increased (P < 0.05) after AE+RE. The results suggest that the increased aerobic capacity shown with AE+RE, was accompanied by a more robust increase in muscle size compared with RE. While this response was not carried over to greater improvement in muscle function, it remains that intense AE can be executed prior to RE without compromising performance outcome.

Keyword
Endurance; Gene expression; Muscle cross-sectional area; Muscle power and strength
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-17710 (URN)10.1152/japplphysiol.01013.2012 (DOI)000313051000011 ()2-s2.0-84871782994 (Scopus ID)
Available from: 2012-12-13 Created: 2012-12-13 Last updated: 2017-06-28Bibliographically approved
3. Acute molecular responses in untrained and trained muscle subjected to aerobic and resistance exercise training versus resistance training alone
Open this publication in new window or tab >>Acute molecular responses in untrained and trained muscle subjected to aerobic and resistance exercise training versus resistance training alone
2013 (English)In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 209, no 4, 283-294 p.Article in journal (Refereed) Published
Abstract [en]

AimThis study assessed and compared acute muscle molecular responses before and after 5-week training, employing either aerobic (AE) and resistance exercise (RE) or RE only. MethodsTen men performed one-legged RE, while the contralateral limb performed AE followed by RE 6h later (AE+RE). Before (untrained) and after (trained) the intervention, acute bouts of RE were performed with or without preceding AE. Biopsies were obtained from m. vastus lateralis of each leg pre- and 3h post-RE to determine mRNA levels of VEGF, PGC-1, MuRF-1, atrogin-1, myostatin and phosphorylation of mTOR, p70S6K, rpS6 and eEF2. ResultsPGC-1 and VEGF expression increased (P<0.05) after acute RE in the untrained, but not the trained state. These markers showed greater response after AE+RE than RE in either condition. Myostatin was lower after AE+RE than RE, both before and after training. AE+RE showed higher MuRF-1 and atrogin-1 expression than RE in the untrained, not the trained state. Exercise increased (P<0.05) p70S6K phosphorylation both before and after training, yet this increase tended to be more prominent for AE+RE than RE before training. Phosphorylation of p70S6K was greater in trained muscle. Changes in these markers did not correlate with exercise-induced alterations in strength or muscle size. ConclusionConcurrent exercise in untrained skeletal muscle prompts global molecular responses consistent with resulting whole muscle adaptations. Yet, training blunts the more robust anabolic response shown after AE+RE compared with RE. This study challenges the concept that single molecular markers could predict training-induced changes in muscle size or strength.

Keyword
concurrent exercise, gene expression, human skeletal muscle, mammalian target of rapamycin, p70S6 kinase
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-20644 (URN)10.1111/apha.12174 (DOI)000326924300007 ()2-s2.0-84887535632 (Scopus ID)
Available from: 2013-12-11 Created: 2013-12-11 Last updated: 2017-12-06Bibliographically approved
4. Exercise-induced AMPK activation does not interfere with muscle hypertrophy in response to resistance training in men
Open this publication in new window or tab >>Exercise-induced AMPK activation does not interfere with muscle hypertrophy in response to resistance training in men
2014 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 116, no 6, 611-620 p.Article in journal (Refereed) Published
Abstract [en]

As aerobic exercise (AE) may interfere with adaptations to resistance exercise (RE), this study explored acute and chronic responses to consecutive AE (similar to 45 min cycling) and RE (4 X 7 maximal knee extensions) vs. RE only. Ten men performed acute unilateral AE + RE interspersed by 15 min recovery. The contralateral leg was subjected to RE. This exercise paradigm was then implemented in a 5-wk training program. Protein phosphorylation, gene expression, and glycogen content were assessed in biopsies obtained from the vastus lateralis muscle of both legs immediately before and 3 h after acute RE. Quadriceps muscle size and in vivo torque were measured, and muscle samples were analyzed for citrate synthase activity and glycogen concentration, before and after training. Acute AE reduced glycogen content (32%; P < 0.05) and increased (P < 0.05) phosphorylation of AMPK (1.5-fold) and rpS6 (1.3-fold). Phosphorylation of p70S6K and 4E-BP1 remained unchanged. Myostatin gene expression was downregulated after acute AE + RE but not RE. Muscle size showed greater (P < 0.05) increase after AE + RE (6%) than RE (3%) training. Citrate synthase activity (18%) and endurance performance (22%) increased (P < 0.05) after AE + RE but not RE. While training increased (P < 0.05) in vivo muscle strength in both legs, normalized and concentric torque increased after RE only. Thus AE activates AMPK, reduces glycogen stores, and impairs the progression of concentric force, yet muscle hypertrophic responses to chronic RE training appear not to be compromised.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:miun:diva-21915 (URN)10.1152/japplphysiol.01082.2013 (DOI)000333183500004 ()2-s2.0-84901058223 (Scopus ID)
Available from: 2014-05-08 Created: 2014-05-08 Last updated: 2017-08-29Bibliographically approved

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