Rune Dueholm Bech

Proliferation of myogenic stem cells in human skeletal muscle in response to low-load resistance training with blood flow restriction

In the last decade muscle training performed using a combination of low external loads and partial restriction of blood flow to the exercising limb has gained increasing interest, since it leads to significant gains in muscle strength and muscle mass. The cellular mechanisms responsible for the muscular adaptations induced by this training paradigm are not fully understood. This study shows that 3 weeks of high‐frequency, low‐intensity muscle exercise with partial blood flow restriction induces increases in maximal muscle strength accompanied by highly marked gains in muscle fibre size. Furthermore, the results indicate that these muscular adaptations rely on a considerable upregulation in myogenic satellite cells number, resulting in nuclear addition to the exercised myofibres. The results contribute to a better understanding of the physiological mechanisms underlying the gain in muscle strength and muscle mass observed with blood flow restricted low‐intensity resistance exercise.

Carbohydrate restricted recovery from long term endurance exercise does not affect gene responses involved in mitochondrial biogenesis in highly trained athletes

The aim was to determine if the metabolic adaptations, particularly PGC‐1α and downstream metabolic genes were affected by restricting CHO following an endurance exercise bout in trained endurance athletes. A second aim was to compare baseline expression level of these genes to untrained. Elite endurance athletes (VO2max 66 ± 2 mL·kg−1·min−1, n = 15) completed 4 h cycling at ~56% VO2max. During the first 4 h recovery subjects were provided with either CHO or only H2O and thereafter both groups received CHO. Muscle biopsies were collected before, after, and 4 and 24 h after exercise. Also, resting biopsies were collected from untrained subjects (n = 8). Exercise decreased glycogen by 67.7 ± 4.0% (from 699 ± 26.1 to 239 ± 29.5 mmol·kg−1·dw−1) with no difference between groups. Whereas 4 h of recovery with CHO partly replenished glycogen, the H2O group remained at post exercise level; nevertheless, the gene expression was not different between groups. Glycogen and most gene expression levels returned to baseline by 24 h in both CHO and H2O. Baseline mRNA expression of NRF‐1, COX‐IV, GLUT4 and PPAR‐α gene targets were higher in trained compared to untrained. Additionally, the proportion of type I muscle fibers positively correlated with baseline mRNA for PGC‐1α, TFAM, NRF‐1, COX‐IV, PPAR‐α, and GLUT4 for both trained and untrained. CHO restriction during recovery from glycogen depleting exercise does not improve the mRNA response of markers of mitochondrial biogenesis. Further, baseline gene expression of key metabolic pathways is higher in trained than untrained.

Skeletal Muscle Remodelling as a Function of Disease Progression in Amyotrophic Lateral Sclerosis

Muscle weakness is considered the pivotal sign of amyotrophic lateral sclerosis (ALS). Knowledge about the skeletal muscle degeneration/regeneration process and the myogenic potential is limited in ALS patients. Therefore, we investigate these processes in a time course perspective by analysing skeletal muscle biopsies from ALS patients collected before and after a 12-week period of normal daily activities and compare these with healthy age-matched control tissue. We do this by evaluating mRNA and protein (immunohistochemical) markers of regeneration, neurodegeneration, myogenesis, cell cycle regulation, and inflammation. Our results show morphological changes indicative of active denervation and reinnervation and an increase in small atrophic fibres. We demonstrate differences between ALS and controls in pathways controlling skeletal muscle homeostasis, cytoskeletal and regenerative markers, neurodegenerative factors, myogenic factors, cell cycle determinants, and inflammatory markers. Our results on Pax7 and MyoD protein expression suggest that proliferation and differentiation of skeletal muscle stem cells are affected in ALS patients, and the myogenic processes cannot overcome the denervation-induced wasting.

Transient impairments in single muscle fibre contractile function after prolonged cycling in elite endurance athletes

Prolonged muscle activity impairs whole‐muscle performance and function. However, little is known about the effects of prolonged muscle activity on the contractile function of human single muscle fibres. The purpose of this study was to investigate the effects of prolonged exercise and subsequent recovery on the contractile function of single muscle fibres obtained from elite athletes.

Local anesthetic wound infiltration for pain management after periacetabular osteotomy A randomized, placebo-controlled, double-blind clinical trial with 53 patients

Background and purpose — To our knowledge, there is no evidence to support the use of local infiltration analgesia (LIA) for postoperative pain relief after periacetabular osteotomy (PAO). We investigated the effect of wound infiltration with a long-acting local anesthetic (ropivacaine) for postoperative analgesia after PAO. Patients and methods — We performed a randomized, double-blind, placebo-controlled trial (ClinicalTrials.gov: NCT00815503) in 53 patients undergoing PAO to evaluate the effect of local anesthetic infiltration on postoperative pain and on postoperative opioid consumption. All subjects received intraoperative infiltration followed by 5 postoperative injections in 10-hour intervals through a multi-holed catheter placed at the surgical site. 26 patients received ropivacaine and 27 received saline. The intervention period was 2 days and the observational period was 4 days. All subjects received patient-controlled opioid analgesia without any restrictions on the total daily dose. Pain was assessed at specific postoperative time points and the daily opioid usage was registered. Results — Infiltration with 75 mL (150 mg) of ropivacaine did not reduce postoperative pain or opioid requirements during the first 4 days. Interpretation — The clinical importance of ropivacaine as single component in postoperative treatment of pain is questionable, and we are planning further studies to explore the potential of LIA in larger volume—and also a multimodal regimen—to treat pain in this category of patients.

The Verbal Rating Scale Is Reliable for Assessment of Postoperative Pain in Hip Fracture Patients.

Background. Hip fracture patients represent a challenge to pain rating due to the high prevalence of cognitive impairment. Methods. Patients prospectively rated pain on the VRS. Furthermore, patients described the changes in pain after raising their leg, with one of five descriptors. Agreement between paired measures on the VRS at rest and by passive straight leg raise with a one-minute interval between ratings at rest and three-minute interval for straight leg raise was expressed by kappa coefficients. Reliability of this assessment of pain using the VRS was compared to the validity of assessing possible change in pain from the selected descriptors. Cognitive status was quantified by the short Orientation-Memory-Concentration Test. Results. 110 patients were included. Paired scores with maximum disagreement of one scale point reached 97% at rest and 95% at straight leg raise. Linear weighted kappa coefficients ranged from 0.68 (95% CI = 0.59–0.77) at leg raise to 0.75 (95% CI = 0.65–0.85) at rest. Unweighted kappa coefficients of agreement in recalled pain compared to agreement of paired VRS scores ranged from 0.57 (95% CI = 0.49–0.65) to 0.36 (95% CI = 0.31–0.41). Interpretation. The VRS is reliable for assessment of pain after hip fracture. The validity of intermittent questioning about possible change in pain intensity is poor.

Delayed Effect of Blood-Flow-Restricted Resistance Training on Rapid Force Capacity

Purpose The aim of the present study was to investigate the effect and time course of high-frequent low-load blood flow–restricted (BFR) resistance training on rapid force capacity (i.e., rate of torque development [RTD]). Materials and Methods Ten male subjects (22.8 ± 2.3 yr) performed four sets of knee extensor exercise (20% one-repetition maximum) to concentric failure during concurrent BFR of the thigh (100 mm Hg), and eight work-matched controls (21.9 ± 3.0 yr) trained without BFR (CON). Twenty-three training sessions were performed within 19 d. Maximal slow and fast knee joint velocity muscle strength and rapid force capacity (e.g., RTD) and evoked twitch contractile parameters were assessed before (Pre) and 5 and 12 d after (Post5 and Post12) training. Muscle biopsies were obtained Pre, after 8 d (Mid8), and 3 and 10 d after (Post3 and Post10) training to examine changes in myofiber area and expression of myocellular proteins known to be modified by cellular stress (CaMKII, annexin A6, SNO-CYS). Results RTD remained unchanged after BFR training at Post5, while increasing 15%–20% Post12 (P < 0.01). Evoked muscle twitch parameters showed a general decline Post5 (P < 0.01) while returning to baseline levels at Post12. All contractile parameters essentially remained unchanged in CON. Elevated CaMKII was observed with BFR training at Post3 (57%) and Post10 (71%) (P < 0.05), whereas SNO-CYS increased in CON at Mid8 (P < 0.05). Conclusion This study is the first to show that low-load resistance exercise performed with BFR leads to marked increases in rapid force capacity (RTD). However, a general delayed adaptive response was observed for voluntary contractile parameters (including RTD) in parallel with a decline and subsequent recovery in evoked contractile properties, suggesting the delayed gain in rapid force capacity mainly have a peripheral origin.

Influence of Resistance Training on Neuromuscular Function and Physical Capacity in ALS Patients

Objectives The present study aimed to explore the effect of resistance training in patients with amyotrophic lateral sclerosis (ALS), a disease characterized by progressive motor neuron loss and muscle weakness. Materials and Methods Following a 12-week “lead-in” control period, a population of ALS patients from Funen, Denmark, completed a 12-week resistance training program consisting of 2-3 sessions/week. Neuromuscular function (strength and power) and voluntary muscle activation (superimposed twitch technique) were evaluated before and after both control and training periods. Physical capacity tests (chair rise and timed up and go), the revised ALS functional rating scale (ALSFRS-R) scores, and muscle cross sectional area (histology) were also assessed. Results Of twelve ALS patients assessed for eligibility, six were included and five completed the study. Training did not significantly affect the ALSFRS-R score, and loss of neuromuscular function (strength and power) increased following the training period. However, an improved functionality (chair rise) and an increase in greatly hypertrophied type II fibres combined with an increase in atrophied fibres following the training period compared to the control period were observed. Conclusion In this small study, the present form of resistance training was unable to attenuate progressive loss of neuromuscular function in ALS, despite some changes in physical capacity and morphology.

High Reliability of a Scoring System for Implant Position in Undisplaced Femoral Neck Fractures

Objectives: The aim of this study was to evaluate the intrarater and interrater reliability of a scoring system for internal fixation (SIFA) in undisplaced femoral neck fractures (FNF). Design: A reproducibility study with a historical consecutive cohort. Setting: The patients were all treated at a level one trauma hospital. Patients/Participants: A cohort of patients with FNF, treated with 2 parallel implants, was retrieved using a local county register, and the cohort was assessed for undisplaced FNF until the desired sample size was reached. One hundred two patients had their x-ray images reviewed 2 times with a minimum 14 days interval, by 3 raters, all blinded for each others results, and an independent person analyzed the data with unweighted kappa statistics. Main Outcome Measurements: Implant positions on the first postoperative anterior-posterior and axial radiographs were first visually assessed, then objectively measured according to SIFA, which consists of 5 individual measurements; screw tip distance, screw femoral shaft angle, inferior screw calcar distance, and screw position in the femoral head in the anterior-posterior and axial radiographs. Results: Visually assessed implant position gave intrarater kappa results for the individual components of SIFA at 0.40–0.75 (rater 1), 0.75–0.98 (rater 2), and 0.69–0.83 (rater 3), with interrater kappa results at 0.18–0.80 (combined range). Objectively measured implant position for the individual components of SIFA gave intrarater kappa results at 0.56–1.0 (rater 1), 0.74–0.89 (rater 2), and 0.81–0.94 (rater 3), with interrater kappa results at 0.56–0.85 (combined range). The overall SIFA score has similar higher intrarater and interrater results for the measured (0.51–0.78) compared with the visual assessment (0.13–0.78). The assessment in the axial view of the screw position in femoral head had the largest difference of acceptable positioning, when comparing visual assessment with the measured. Conclusions: The SIFA demonstrates substantial intrarater and interrater reliability (kappa 0.51–0.78), when raters make measurements of radiographs, but lower reliability (kappa 0.13–0.78) when raters visually assess the radiographs without measuring. The SIFA should be assessed on a large cohort, for correlation with clinical evaluation.