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Andersen L.L.,Helmholtz Center Munich | Andersen J.L.,Institute of Sports Medicine Copenhagen | Zebis M.K.,Helmholtz Center Munich | Aagaard P.,University of Southern Denmark
Scandinavian Journal of Medicine and Science in Sports | Year: 2010

The objective of this study is to investigate the potentially opposing influence of qualitative and quantitative muscular adaptations in response to high-intensity resistance training on contractile rate of force development (RFD) in the early (<100 ms) and later phases (>200 ms) of rising muscle force. Fifteen healthy young males participated in a 14-week resistance training intervention for the lower body and 10 matched subjects participated as controls. Maximal muscle strength (MVC) and RFD were measured during maximal voluntary isometric contraction of the quadriceps femoris muscle. Muscle biopsies were obtained from the vastus lateralis. The main findings were that RFD in the late phase of rising muscle force increased in response to resistance training whereas early RFD remained unchanged and early relative RFD (i.e., RFD/MVC) decreased. Quantitatively, muscle fiber cross-sectional area and MVC increased whereas, qualitatively, the relative proportion of type IIX muscle fibers decreased. Multiple regression analysis showed that while increased MVC positively influenced both early and late RFD, decreased-type IIX negatively influenced early RFD only. In conclusion, early and late RFD responded differently to high-intensity resistance training due to differential influences of qualitative and quantitative muscular adaptations on early and later phases of rising muscle force. © 2009 John Wiley & Sons A/S. Source

Lauersen J.B.,Institute of Sports Medicine Copenhagen | Andersen L.B.,University of Southern Denmark | Andersen L.B.,Norwegian School of Sport Sciences
British Journal of Sports Medicine | Year: 2014

Background Physical activity is important in both prevention and treatment of many common diseases, but sports injuries can pose serious problems. Objective To determine whether physical activity exercises can reduce sports injuries and perform stratified analyses of strength training, stretching, proprioception and combinations of these, and provide separate acute and overuse injury estimates. Material and methods PubMed, EMBASE, Web of Science and SPORTDiscus were searched and yielded 3462 results. Two independent authors selected relevant randomised, controlled trials and quality assessments were conducted by all authors of this paper using the Cochrane collaboration domain-based quality assessment tool. Twelve studies that neglected to account for clustering effects were adjusted. Quantitative analyses were performed in STATAV.12 and sensitivity analysed by intention-to-treat. Heterogeneity (I2) and publication bias (Harbord's small-study effects) were formally tested. Results 25 trials, including 26 610 participants with 3464 injuries, were analysed. The overall effect estimate on injury prevention was heterogeneous. Stratified exposure analyses proved no beneficial effect for stretching (RR 0.963 (0.846-1.095)), whereas studies with multiple exposures (RR 0.655 (0.520-0.826)), proprioception training (RR 0.550 (0.347-0.869)), and strength training (RR 0.315 (0.207-0.480)) showed a tendency towards increasing effect. Both acute injuries (RR 0.647 (0.502-0.836)) and overuse injuries (RR 0.527 (0.373-0.746)) could be reduced by physical activity programmes. Intention-to-treat sensitivity analyses consistently revealed even more robust effect estimates. Conclusions Despite a few outlying studies, consistently favourable estimates were obtained for all injury prevention measures except for stretching. Strength training reduced sports injuries to less than 1/3 and overuse injuries could be almost halved. Source

Bendiksen M.,Copenhagen University | Bischoff R.,Copenhagen University | Randers M.B.,Copenhagen University | Mohr M.,Copenhagen University | And 7 more authors.
Medicine and Science in Sports and Exercise | Year: 2012

Introduction: The aims of the study were 1) to evaluate whether a multifaceted simulated soccer game protocol, entitled the Copenhagen Soccer Test (CST), elicited a similar physiological loading as a competitive game (CG) and 2) to determine muscle metabolites, blood variables, and sprint performance in various phases of CST. Methods: Twelve Danish Second-and Third-Division soccer players participated in the study. On separate days, HR measurements, frequent blood sampling, and physical/technical tests were performed during 60-and 90-min versions of the CST during which repeated musculus vastus lateralis biopsies were collected. A CG was also played, where HR was recorded and pre-and post-game muscle biopsies and blood samples were collected. Results: No differences were observed between CST and CG in average HR (85% ± 1% and 86% ± 1% HRmax, P > 0.05) or recovery plasma creatine kinase (24 h: 312 ± 57 and 324 ± 76 U•L, P > 0.05). Muscle glycogen decreased (P < 0.05) from 459 ± 15 to 232 ± 30 mmol•kg dry weight (d.w.) during CST, which was not different from CG (P > 0.05). The rate of glycogen utilization was 4 ± 1 mmol•kg d.w.•min during the warm-up and the first 15 min of CST and 1 ± 1 mmol•kg d.w.•min (P < 0.05) from 60 to 90 min of CST. After 15 min of CST, muscle lactate was elevated (P < 0.05) approximately fivefold (24 ± 3 mmol•kg d.w.), and creatine phosphate was lowered (P < 0.05) by ∼60% (28 ± 4 mmol•kg d.w.). Sprint velocity (2 × 20 m) decreased (P < 0.05) by 7% during CST (5.2 ± 0.6 to 4.9 ± 0.7 m•s-1). Conclusions: The physiological response to the CST was reproducible and comparable to that of high-level CG. The CST allowed for rapid muscle sampling and revealed high creatine phosphate degradation throughout the test and a lowered glycogen utilization toward the end of the simulated game. © 2012 by the American College of Sports Medicine. Source

Kraunsoe R.,Copenhagen University | Boushel R.,Copenhagen University | Hansen C.N.,Copenhagen University | Schjerling P.,Institute of Sports Medicine Copenhagen | And 4 more authors.
Journal of Physiology | Year: 2010

Adipose tissue exerts important endocrine and metabolic functions in health and disease. Yet the bioenergetics of this tissue is not characterized in humans and possible regional differences are not elucidated. Using high resolution respirometry, mitochondrial respiration was quantified in human abdominal subcutaneous and intra-abdominal visceral (omentum majus) adipose tissue from biopsies obtained in 20 obese patients undergoing bariatric surgery. Mitochondrial DNA (mtDNA) and genomic DNA (gDNA) were determined by the PCR technique for estimation of mitochondrial density. Adipose tissue samples were permeabilized and respirometric measurements were performed in duplicate at 37°C. Substrates (glutamate (G) + malate (M) + octanoyl carnitine (O) + succinate (S)) were added sequentially to provide electrons to complex I + II. ADP (D) for state 3 respiration was added after GM. Uncoupled respiration was measured after addition of FCCP. Visceral fat contained more mitochondria per milligram of tissue than subcutaneous fat, but the cells were smaller. Robust, stable oxygen fluxes were found in both tissues, and coupled state 3 (GMOSD) and uncoupled respiration were significantly (P < 0.05) higher in visceral (0.95 ± 0.05 and 1.15 ± 0.06 pmol O2 s-1 mg-1, respectively) compared with subcutaneous (0.76 ± 0.04 and 0.98 ± 0.05 pmol O2 s-1 mg-1, respectively) adipose tissue. Expressed per mtDNA, visceral adipose tissue had significantly (P < 0.05) lower mitochondrial respiration. Substrate control ratios were higher and uncoupling control ratio lower (P < 0.05) in visceral compared with subcutaneous adipose tissue. We conclude that visceral fat is bioenergetically more active and more sensitive to mitochondrial substrate supply than subcutaneous fat. Oxidative phosphorylation has a higher relative activity in visceral compared with subcutaneous adipose tissue. © 2010 The Authors. Journal compilation © 2010 The Physiological Society. Source

Nedergaard A.,Nordic Bioscience Biomarkers and Research | Nedergaard A.,Institute of Sports Medicine Copenhagen | Henriksen K.,Nordic Bioscience Biomarkers and Research | Karsdal M.A.,Nordic Bioscience Biomarkers and Research | Christiansen C.,Nordic Bioscience Biomarkers and Research
Best Practice and Research: Clinical Obstetrics and Gynaecology | Year: 2013

Loss of musculoskeletal mass and function is a natural ageing trait, reinforced by an unhealthy life style. Loss of bone (osteoporosis) and muscle (sarcopaenia) are conditions whose prevalence are increasing because of the change in population distribution in the western world towards an older mean age. Improvements in lifestyle factors, such as diet, smoking and exercise, are the most powerful tools to combat this decline efficiently; however, public health interventions aimed at tackling these problems have shown abysmal success at the population level, mostly due to failure in compliance. With these issues in mind, we believe that the primary prevention modality in coming decades will be pharmacological. We review the basic biology of musculoskeletal ageing and what measures can be taken to prevent ageing-associated loss of musculoskeletal mass and function, with particular emphasis on pharmacological means. © 2013 Elsevier Ltd. All rights reserved. Source

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