Institute of Sports Medicine Copenhagen

science, Denmark

Institute of Sports Medicine Copenhagen

science, Denmark
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PubMed | University Institute of Health Sciences, Bispebjerg Hospital, Copenhagen University and Institute of Sports Medicine Copenhagen
Type: | Journal: Journal of applied physiology (Bethesda, Md. : 1985) | Year: 2016

Non-steroidal anti-inflammatory drugs (NSAID) are used as pain killers during periods of unloading caused by traumatic occurrences or diseases. However, it is unknown how the tendon protein turnover and mechanical properties responds to unloading and subsequent loading in elderly humans, and especially whether NSAIDs affect tendon adaptation during such periods. Thus, we studied the influence of NSAID upon the human patellar tendon protein synthesis and mechanical properties during immobilization and subsequent rehabilitating resistance training.19 men (60-80 yrs, range) were randomly assigned to NSAID (Ibuprofen 1200 mg/d, Ibu) or placebo (Plc). One lower limb was immobilized in a cast for two weeks and retrained for six weeks. Tendon collagen protein synthesis, expression of gene related to collagen turnover and remodeling, size, signal intensity (from magnetic resonance imaging), and mechanical properties were investigated.Tendon collagen synthesis decreased (p<0.001), whereas tendon size and mechanical properties were generally unchanged with immobilization, and NSAID treatment did not influence this. Matrix metalloproteinase-2 mRNA tended to increase (p<0.1) after immobilization in both groups, whereas scleraxis mRNA decreased with inactivity in the Plc group only (p<0.05).In elderly human tendons, collagen protein synthesis decreased after two weeks of immobilization, whereas tendon stiffness and modulus were only marginally reduced, and NSAID had no influence upon this. This indicates an importance of mechanical loading for maintenance of tendon collagen turnover. However, reduced collagen production induced by short-term unloading may only marginally affect tendon mechanical properties in elderly individuals.

PubMed | Arla Foods, Bispebjerg Hospital, University of Utah, Copenhagen University and Institute of Sports Medicine Copenhagen
Type: | Journal: American journal of physiology. Endocrinology and metabolism | Year: 2016

The present study investigated whether well-tolerated light-load resistance exercise (LL-RE) affects skeletal muscle fractional synthetic rate (FSR) and anabolic intracellular signaling as a way to counteract age-related loss of muscle mass.Untrained healthy men (age: +65 yrs) were subjected to 13 hours supine rest. After 21/2 hours of rest, unilateral LL-RE was conducted consisting of leg extensions (10 sets, 36 repetitions) at 16% 1RM. Subsequently, the subjects were randomized to oral intake of PULSE (4g whey protein/hour; N=10), BOLUS (28g whey protein at 0 hours and 12g whey protein at 7 hours post-exercise; N=10) or placebo (4g maltodextrin/hour; N=10). Quadriceps muscle biopsies were taken at 0, 3, 7 and 10 hours post-exercise from both the resting and exercised leg. Myofibrillar-FSR and activity of select targets from the mTORC1-signalling cascade were analyzed from the biopsies.LL-RE increased myofibrillar-FSR compared to the resting leg throughout the 10h post-exercise period. The p-AKT (T308) expression increased in the exercise leg immediately after exercise. This increase persisted in the placebo group only. Levels of p-4E-BP1 (T37/46) increased throughout the post-exercise period in the exercised leg in the placebo and BOLUS group and peaked at 7h. In all three groups, p-eEF2 (T56) decreased in response to LL-RE.We conclude that resistance exercise at only 16% 1RM increased myofibrillar-FSR, irrespective of nutrient type and feeding pattern, which indicates an anabolic effect of LL-RE in elderly individuals. This finding was supported by increased signaling for translation initiation and translation elongation in response to LL-RE.

Petersen S.G.,Institute of Sports Medicine Copenhagen | Saxne T.,Lund University | Heinegard D.,Lund University | Hansen M.,Institute of Sports Medicine Copenhagen | And 6 more authors.
Osteoarthritis and Cartilage | Year: 2010

Objective: To investigate changes in levels of serum cartilage oligomeric matrix protein (COMP) and urine c-telopeptide of type-2 collagen (CTX-II) as markers for cartilage turnover in patients with osteoarthritis (OA) of the knee, in response to muscle strength training in combination with treatment with glucosamine, ibuprofen or placebo. Design: A 12-week double blind, placebo controlled, randomized study. Method: Thirty-six elderly patients with bilateral tibiofemoral knee OA determined by radiography were randomly assigned to treatment with glucosamine (n = 12), ibuprofen (n = 12) or placebo (n = 12) during 12 weeks of strength training of both legs with focus on the quadriceps muscle. Strength tests (5 repetition maximum), blood and urine sampling were performed before and after the training period. Serum COMP and urinary CTX-II were measured by enzyme-linked immunosorbent assay (ELISA). Results: All three groups increased their muscle strength following 12 weeks of strength training (P < 0.001). Serum COMP levels were reduced in the glucosamine-treated group after the training period (P = 0.012), whereas they did not change in the two other groups. Glucosamine reduced COMP statistically significant compared to both placebo and ibuprofen; the mean reduction with glucosamine was 13% vs placebo (P = 0.0378) and 17% vs ibuprofen (P = 0.0122). Urinary CTX-II levels did not change significantly in any of the three experimental groups. Conclusion: Serum COMP decreased significantly over the 12-week training period when treatment with glucosamine was added to the training regimen. This suggests an effect by glucosamine on the response of the OA cartilage to a period of joint loading in humans with knee OA. © 2009 Osteoarthritis Research Society International.

PubMed | Institute of Sports Medicine Copenhagen
Type: Journal Article | Journal: The American journal of sports medicine | Year: 2013

The Achilles tendon is one of the strongest tendons in the human body, and yet it frequently ruptures, which is a substantial clinical problem. However, the cause of ruptures remains elusive.Ruptured human Achilles tendon displays inferior biomechanical properties and altered collagen composition compared with noninjured tendon.Controlled laboratory study.Biopsy specimens were obtained at the rupture site and the noninjured part of the tendon (internal controls) in 17 patients with acute Achilles tendon rupture. Age- and weight-matched human cadaveric Achilles tendons (external controls) were also obtained. Tendon samples were tested micromechanically and biochemically.The mean Young modulus was lower (P < .01) in ruptured (256.7 100.8 MPa) and internal control tendon (262.4 111.5 MPa) compared with external control tendon (512.9 209.6 MPa; P < .01), whereas failure strength did not display similar differences (P = .06-.16). Collagen content, lysyl pyridinoline (LP), hydroxylysyl pyridinoline (HP), and pentosidine (PENT) did not display regional differences between ruptured and noninjured tendon. However, collagen content was less in ruptured (0.457 0.093 mg/mg) and noninjured tendon (0.476 0.072 mg/mg) compared with external control tendon (0.585 0.044 mg/mg, P < .001). Pentosidine was similar in all tendon samples and was positively related to age in all samples (r2 = 0.44-0.72, P < .05). Collagen content was positively related to failure stress but only in ruptured samples (r2 = 0.36; P < .05). HP, LP, and PENT content were unrelated to failure stress and Young modulus in ruptured, noninjured, and cadaveric tendon.These data imply that there may be a mechanical weakening of the tendon and that a reduced collagen content may be related to the pathophysiological characteristics of Achilles tendon rupture.Earlier studies have demonstrated that specific training regimens to treat tendon injury can improve tendon composition and mechanical properties. This study supports the notion that treatment measures should aim to increase tendon collagen content and improve micromechanical quality of the tendon matrix.

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