Peter Magnusson

Changes in satellite cells in human skeletal muscle after a single bout of high intensity exercise

No studies to date have reported activation of satellite cells in vivo in human muscle after a single bout of high intensity exercise. In this investigation, eight individuals performed a single bout of high intensity exercise with one leg, the contralateral leg being the control. A significant increase in mononuclear cells staining for the neural cell adhesion molecule (N‐CAM) and fetal antigen 1 (FA1) were observed within the exercised human vastus lateralis muscle on days 4 and 8 post exercise. In addition, a significant increase in the concentration of the FA1 protein was determined in intramuscular dialysate samples taken from the vastus lateralis muscle of the exercising leg (day 0: 1.89 ± 0.82 ng ml−1; day 2: 1.68 ± 0.37 ng ml−1; day 4: 3.26 ± 1.29 ng ml−1, P < 0.05 versus basal; day 8: 4.68 ± 2.06 ng ml−1, P < 0.05 versus basal and control). No change was noted in the control leg. Despite this increase in N‐CAM‐ and FA1‐positive mononuclear cells, an increased expression of myogenin and the neonatal isoform of the myosin heavy chain (MHCn) was not observed. Interestingly, myofibre lesions resulting from extensive damage to the proteins within the myofibre, particularly desmin or dystrophin, were not observed, and hence did not appear to induce the expression of either N‐CAM or FA1. We therefore propose that satellite cells can be induced to re‐enter the cell growth cycle after a single bout of unaccustomed high intensity exercise. However, a single bout of exercise is not sufficient for the satellite cell to undergo terminal differentiation.

Extracellular matrix adaptation of tendon and skeletal muscle to exercise.

The extracellular matrix (ECM) of connective tissues enables linking to other tissues, and plays a key role in force transmission and tissue structure maintenance in tendons, ligaments, bone and muscle. ECM turnover is influenced by physical activity, and both collagen synthesis and metalloprotease activity increase with mechanical loading. This can be shown by determining propeptide and proteinase activity by microdialysis, as well as by verifying the incorporation of infused stable isotope amino acids in biopsies. Local tissue expression and release of growth factors for ECM such as IGF‐1, TGF‐beta and IL‐6 is enhanced following exercise. For tendons, metabolic activity (e.g. detected by positron emission tomography scanning), circulatory responses (e.g. as measured by near‐infrared spectroscopy and dye dilution) and collagen turnover are markedly increased after exercise. Tendon blood flow is regulated by cyclooxygenase‐2 (COX‐2)‐mediated pathways, and glucose uptake is regulated by specific pathways in tendons that differ from those in skeletal muscle. Chronic loading in the form of physical training leads both to increased collagen turnover as well as to some degree of net collagen synthesis. These changes modify the mechanical properties and the viscoelastic characteristics of the tissue, decrease its stress‐susceptibility and probably make it more load‐resistant. The mechanical properties of tendon fascicles vary within a given human tendon, and even show gender differences. The latter is supported by findings of gender‐related differences in the activation of collagen synthesis with exercise. These findings may provide the basis for understanding tissue overloading and injury in both tendons and skeletal muscle.

Increased inversion angle replication error in functional ankle instability.

Abstract The inversion-angle replication error of the ankle joint was measured in subjects with a functionally stable or unstable ankle. Testing was performed as a passive set–active replication design. The absolute replication error on the unstable side of 23 unilaterally, functionally, and mechanically unstable subjects was found to be significantly greater (2.5°) than the error on the healthy contralateral side (2.0°; P < 0.05) and the error in a group of 40 ankle healthy controls (1.7°; P < 0.01). In 10 ankle-healthy high-level cross-country runners the replication error was reduced by 38% after warming up (P = 0.04).

Hip Adduction and Abduction Strength Profiles in Elite Soccer Players: Implications for Clinical Evaluation of Hip Adductor Muscle Recovery After Injury

Background: An ipsilateral hip adduction/abduction strength ratio of more than 90%, and hip adduction strength equal to that of the contralateral side have been suggested to clinically represent adequate strength recovery of hip adduction strength in athletes after groin injury. However, to what extent side-to-side symmetry in isometric hip adduction and abduction strength can be assumed in soccer players remains uncertain. Purpose: To compare isometric hip adduction and abduction strength on the dominant and nondominant side in injury-free soccer players. Study Design: Cross-sectional study; Level of evidence, 3. Methods: One hundred elite soccer players were included. Maximal unilateral isometric hip adduction and abduction strength on the dominant and nondominant side were measured with a handheld dynamometer, using a reliable test procedure. Results: The dominant side was stronger than the nondominant side for both isometric hip adduction (2.45 ± 0.54 vs 2.37 ± 0.48 Nm/kg, P = .02) and hip abduction (2.35 ± 0.33 vs 2.25 ± 0.31 Nm/kg, P < .001), corresponding to a 3% and 4% difference, respectively. Isometric hip adduction was greater than isometric hip abduction for both the dominant (2.44 ± 0.53 vs 2.35 ± 0.33 Nm/kg, P = .04) and nondominant (2.37 ± 0.48 vs 2.26 ± 0.33 Nm/kg, P = .03) side. Isometric hip adduction/abduction ratio was not different between the dominant (1.04 ± 0.18) and nondominant (1.06 ± 0.17, P = .40) side. A post hoc analysis showed that isometric hip adduction/abduction ratio was significantly lower in players with groin pain during hip adduction testing compared with players with a pain-free test (0.80 ± 0.14, P < .001) Conclusion: The marginal difference between the dominant and the nondominant side is within the measurement variation of the test procedure, and contralateral isometric hip adduction strength can therefore be used as a simple clinical reference point of full recovery of hip adduction muscle strength in soccer players. Furthermore, it is suggested that the ipsilateral hip adduction/abduction strength ratio is used as a guideline for evaluating hip adduction strength recovery in soccer players with bilateral groin problems.

Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: A Randomized Controlled Trial.

Background: Previous studies have shown that eccentric training has a positive effect on Achilles tendinopathy, but few randomized controlled trials have compared it with other loading-based treatment regimens. Purpose: To evaluate the effectiveness of eccentric training (ECC) and heavy slow resistance training (HSR) among patients with midportion Achilles tendinopathy. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 58 patients with chronic (>3 months) midportion Achilles tendinopathy were randomized to ECC or HSR for 12 weeks. Function and symptoms (Victorian Institute of Sports Assessment–Achilles), tendon pain during activity (visual analog scale), tendon swelling, tendon neovascularization, and treatment satisfaction were assessed at 0 and 12 weeks and at the 52-week follow-up. Analyses were performed on an intention-to-treat basis. Results: Both groups showed significant (P < .0001) improvements in Victorian Institute of Sports Assessment–Achilles and visual analog scale from 0 to 12 weeks, and these improvements were maintained at the 52-week follow-up. Concomitant with the clinical improvement, there was a significant reduction in tendon thickness and neovascularization. None of these robust clinical and structural improvements differed between the ECC and HSR groups. However, patient satisfaction tended to be greater after 12 weeks with HSR (100%) than with ECC (80%; P = .052) but not after 52 weeks (HSR, 96%; ECC, 76%; P = .10), and the mean training session compliance rate was 78% in the ECC group and 92% in the HSR group, with a significant difference between groups (P < .005). Conclusion: The results of this study show that both traditional ECC and HSR yield positive, equally good, lasting clinical results in patients with Achilles tendinopathy and that the latter tends to be associated with greater patient satisfaction after 12 weeks but not after 52 weeks.

Glutaraldehyde Cross-Linking of Tendon—Mechanical Effects at the Level of the Tendon Fascicle and Fibril

Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from ∼8 MPa to ∼39 MPa. The mechanical effects of glutaraldehyde at the tendon fibril level were examined by atomic force microscopy. Peak forces increased from ∼1379 to ∼2622 pN while an extended Hertz fit of force-indentation data showed a ∼24 fold increase in Youngs modulus on indentation. The effect of glutaraldehyde cross-linking on the tensile properties of a single collagen fibril was investigated by a novel methodology based on atomic force spectroscopy. The Youngs modulus of a secluded fibril increased from ∼407 MPa to ∼1.1 GPa with glutaraldehyde treatment. Collectively, the findings indicate that cross-linking at the level of the collagen fibril is of key importance for the mechanical strength of tendon tissue. However, when comparing the effects at the level of the tendon fascicle and fibril, respectively, further questions are prompted regarding the pathways of force through the tendon microstructure as fibril strength seems to surpass that of the tendon fascicle.

Variability and reproducibility of hepatic FDG uptake measured as SUV as well as tissue-to-blood background ratio using positron emission tomography in healthy humans

Introduction:  To investigate variability and reproducibility of hepatic [18F]‐2‐fluoro‐2‐deoxy‐d‐glucose (FDG) uptake in healthy individuals.

Meniscus transplantation – consensus declaration

On September 5 , 1998 a number of orthopaedic surgeons from Denmark and Sweden met at Bispebjerg Hospital in Copenhagen, Denmark to have a consensus discussion about meniscal transplantion, based on the information and views presented at a symposium held the previous two days. The consensus discussion was divided into two sections: first a general consensus was achieved, followed by a discussion and agreement about whether meniscal transplantation should be offered as a treatment option in Denmark. The consensus group could consult a board of experts: Clinical professor Marlowe Goble, M.D.E. (Salt Lake City, Utah, USA), Professor Dieter Kohn, M.D., dr. med. (HomburglSaar, Germany), Professor Rend Verdonk, M.D., Ph.D. (Gent, Belgium), Assistant professor Karola Messner, M.D., Ph.D. (Linkoping, Sweden), Henrik Aagaard, M.D., Ph.D. (Copenhagen, Denmark), and Benn Duus, M.D. (Copenhagen, Denmark). The views and opinions presented in the consensus are not necessarily shared by all members of this advisory board.

Hyperpolarized (13)C MR Angiography.

Magnetic resonance angiography (MRA) is a non-invasive technology that can be used for diagnosis and monitoring of cardiovascular disease; the number one cause of mortality worldwide. Hyperpolarized imaging agents provide signal enhancement of more than 10, 000 times, which implies large reduction in acquisition time and improved spatial resolution. We review the role of hyperpolarized 13C agents for MR angiography and present the literature in the field. Furthermore, we present a study of the benefit of intra-arterial injection over intravenous injection of hyperpolarized agent for cerebral angiography in the rat, and compare the performance of two standard angiographic pulse sequences, the gradient echo (GRE) sequence and the balanced steady-state free precession (bSSFP). 2D coronal cerebral angiographies using intra-arterial injections were acquired with a GRE sequence with in-plane resolution of 0.27 mm and matrix size 256x128, and 2D coronal cerebral angiographies were acquired with a bSSFP sequence with in-plane resolution of 0.55 mm and matrix size 128x64. The bSSFP sequence provides higher SNR in phantoms than the GRE sequence. Similarly, intravenous injections are imaged with higher SNR with the bSSFP sequence, where the signal destruction of the GRE sequence is avoided. However, for intra-arterial injections, the bSSFP sequence results in strong artefacts, and the GRE sequence is preferred. Hyperpolarized MRA presents many challenges and cannot currently compete with conventional contrast enhanced MRA. Further research may change this since hyperpolarization is still an immature methodology.

The dilemma of sports medicine

As a medical doctor or a therapist working in the field of sports medicine, we are constantly subjected to major challenges and dilemmas. On the one hand, we try to use evidence‐based treatments to cure injuries or medical problems in our sports medicine patients to have them recover and return to sports. On the other hand, we are getting pressure from the athletes, coaches, and club‐officials/ sponsors to get the athlete ready for competition as quickly as possible, even when there is no documented cure or when the known regeneration time is far longer that the athlete and (very often) the people around them can accept. Often, placebo (or superficial undocumented activities used as “treatment”) is used by doctors to help the athletes. The insightful doctor knows when to use harmless “treatments” and when to abstain from the use of undocumented procedures (e.g., injections, infusions, some surgery) that can potentially cause side effects. It should be a goal for sports medicine doctors to encourage research towards any treatment procedure where no evidence exists so far. Clearly, the practice of sports medicine takes place in the real world, and there is a constant pressure on the sports physician—not the least due to economic interests in top sports. Doctors are often put under pressure or may even be overruled regarding how quickly and how much an athlete recovering from an injury can be active in competitive sports. It can be tempting as a therapist to quietly accept this and go into “treatment” action before scientific proof is established. Nevertheless, it is important to “fight back” and insist on the scientific basis of all treatments including in sports medicine. Many sports injuries have well‐documented treatments today, but we are still not in a perfect shape. Even the best‐documented treatments reveal a success rate of 70%‐ 80%, leaving a substantial number of athletes “un‐healed,” and several treatments show a large variation in the treatment response of the individual athlete. Whereas this can seem frustrating and often will challenge the treatment alliance between doctor and athletes, it should be considered a stimulus to investigate combinations of treatments as well as trying to identify specific markers for the individual that can differentiate the treatment in the individual athlete. The better the theoretical basis for tissue recovery and the clinical rehabilitation in relation to sports injury can interact with each other, the more academic credibility the sports medicine area will get, and in the long run, this will lead to treatments that help the athletes the most.