Klavs Madsen

Maximal voluntary contraction force, SR function and glycogen resynthesis during the first 72 h after a high-level competitive soccer game

The aim of this study was to examine maximal voluntary knee-extensor contraction force (MVC force), sarcoplasmic reticulum (SR) function and muscle glycogen levels in the days after a high-level soccer game when players ingested an optimised diet. Seven high-level male soccer players had a vastus lateralis muscle biopsy and a blood sample collected in a control situation and at 0, 24, 48 and 72xa0h after a competitive soccer game. MVC force, SR function, muscle glycogen, muscle soreness and plasma myoglobin were measured. MVC force sustained over 1xa0s was 11 and 10% lower (Pxa0<xa00.05) after 0 and 24xa0h, respectively, compared with control. The rate of SR Ca2+ uptake at 800xa0nM [Ca2+]free was lower (Pxa0<xa00.05) after 0xa0h (2.5xa0μmol Ca2+xa0gxa0prot−1xa0min−1) than for all other time points (24xa0h: 5.1xa0μmol Ca2+xa0g prot−1xa0min−1). However, SR Ca2+ release rate was not affected. Plasma myoglobin was sixfold higher (Pxa0<xa00.05) immediately after the game, but normalised 24xa0h after the game. Quadriceps muscle soreness (0–10 VAS-scale) was higher (Pxa0<xa00.05) after 0xa0h (3.6), 24xa0h (1.8), 48xa0h (1.1) and 72xa0h (1.4) compared with control (0.1). Muscle glycogen was 57 and 27% lower (Pxa0<xa00.001) 0 and 24xa0h after the game compared with control (193 and 328 vs. 449xa0mmolxa0kgxa0dxa0w−1). In conclusion, maximal voluntary contraction force and SR Ca2+ uptake were impaired and muscle soreness was elevated after a high-level soccer game, with faster recovery of SR function in comparison with MVC force, soreness and muscle glycogen.

Carbohydrate supercompensation and muscle glycogen utilization during exhaustive running in highly trained athletes

SummaryThree female and three male highly trained endurance runners with mean maximal oxygen uptake (VO2max) values of 60.5 and 71.5 ml·kg−1·min−1, respectively, ran to exhaustion at 75%–80% of VO2max on two occasions after an overnight fast. One experiment was performed after a normal diet and training regimen (Norm), the other after a diet and training programme intended to increase muscle glycogen levels (Carb). Muscle glycogen concentration in the gastrocnemius muscle increased by 25% (P<0.05) from 581 mmol·kg−1 dry weight, SEM 50 to 722 mmol·kg−1 dry weight, SEM 34 after Carb. Running time to exhaustion, however, was not significantly different in Carb and Norm, 77 min, SEM 13 vs 70 min, SEM 8, respectively. The average glycogen concentration following exhaustive running was 553 mmol· kg−1 dry weight, SEM 70 in Carb and 434 mmol·kg−1 dry weight, SEM 57 in Norm, indicating that in both tests muscle glycogen stores were decreased by about 25%. Periodic acid-Schiff staining for semi-quantitative glycogen determination in individual fibres confirmed that none of the fibres appeared to be glycogen-empty after exhaustive running. The steady-state respiratory exchange ratio was higher in Carb than in Norm (0.92, SEM 0.01 vs 0.89, SEM 0.01; P<0.05). Since muscle glycogen utilization was identical in the two tests, the indication of higher utilization of total carbohydrate appears to be related to a higher utilization of liver glycogen. We have concluded that glycogen depletion of the gastrocnemius muscle is unlikely to be the cause of fatigue during exhaustive running at 75%–80% of VO2max in highly trained endurance runners. Furthermore, diet- and training-induced carbohydrate supercompensation does not appear to improve endurance capacity in such individuals.

Field measurements of oxygen uptake in elite orienteers during cross-country running using telemetry

Oxygen uptake (Vo2) was measured and economy calculated during running on a treadmill and during cross‐country running in 14 male and 9 female orienteers using a telemetric system (K‐2, Cosmed, Italy). The cross‐country route comprised 3 parts: horizontal path running, horizontal running in light terrain and running in heavy terrain with obstacles and steep hills. Each subject accomplished the whole test route at a speed corresponding to 96±5% of maximal speed and at maximal speed. The running time at maximal speed was 19±3 min. The running economy was similar in treadmill and path running (211 ± 10 vs 210± 14 ml · kg−1· km−1), but Vo2 per km increased in light and heavy terrain to 290 ± 16 and 362±18 ml · kg−1· km−1, respectively. There was no difference in running economy between men and women. The elite group (5 men and 3 women) demonstrated 5% better running economy than the sub‐elite (9 men and 6 women) during running in light and heavy terrain, whereas no difference was seen during treadmill and path running. In conclusion, elite orienteers have better running economy in light and heavy terrain than sub‐elite orienteers.

Obesity augments the age-induced increase in mitochondrial capacity for H2O2 release in Zucker fatty rats

Aim:u2002 Mitochondrial dysfunction has been suggested to play a significant role in obesity and insulin resistance. The aim of the present study was to investigate if changes in obesity and insulin resistance were related to similar changes in mitochondrial capacity for hydrogenperoxide release in Zucker diabetic fatty rats and their lean littermates.

Mechanical Muscle Function and Lean Body Mass During Supervised Strength Training and Testosterone Therapy in Aging Men with Low-Normal Testosterone Levels

To examine the effect of strength training and testosterone therapy on mechanical muscle function and lean body mass (LBM) in aging men with low‐normal testosterone levels in a randomized, double‐blind, placebo‐controlled 24‐week study.

Effect of whey protein- and carbohydrate-enriched diet on glycogen resynthesis during the first 48 h after a soccer game

The effect of a whey protein‐ and carbohydrate (CHO)‐enriched diet on the rate of muscle glycogen resynthesis after a soccer match was examined. Sixteen elite soccer players were randomly assigned to a group ingesting a diet rich in carbohydrates and whey protein [CHO, protein, and fat content was 71, 21, and 8E%, respectively; high content of carbohydrates and whey protein (HCP), nu2009=u20099] or a group ingesting a normal diet (55, 18, and 26E%; control [CON], nu2009=u20097) during a 48‐h recovery period after a soccer match. CON and three additional players carried out a 90‐ and 60‐min simulated match without body contacts (SIM90 and SIM60). Muscle glycogen was lowered (Pu2009<u20090.05) by 54, 48, 53, and 38% after the matches in CON, HCP, SIM90, and SIM60, respectively. Glycogen resynthesis during the first 48u2009h after the match was not different between CON and HCP, whereas glycogen resynthesis was slower (Pu2009<u20090.05) during the first 24u2009h after SIM60 than SIM90 (2.88u2009±u20090.84 vs 4.32u2009±u20090.54u2009mmol/kgu2009dw/h). In HCP, glycogen content in type II muscle fibers was still lowered 48u2009h after the match. In conclusion, glycogen resynthesis 48u2009h after a soccer match is not elevated by ingestion of a HCP diet. Furthermore, glycogen resynthesis does not appear to be impaired by body contacts during a match.

Effect of Whey Protein Hydrolysate on Performance and Recovery of Top-Class Orienteering Runners

This trial aimed to examine the effect of whey protein hydrolysate intake before and after exercise sessions on endurance performance and recovery in elite orienteers during a training camp. Eighteen elite orienteers participated in a randomized controlled intervention trial during a 1-week training camp (13 exercise sessions). Half of the runners (PRO-CHO) ingested a protein drink before (0.3 g kg(-1)) and a protein-carbohydrate drink after (0.3 g protein kg(-1) and 1 g carbohydrate kg(-1)) each exercise session. The others ingested energy and time-matched carbohydrate drinks (CHO). A 4-km run-test with 20 control points was performed before and on the last day of the intervention. Blood and saliva were obtained in the mornings, before and after run-tests, and after the last training session. During the intervention, questionnaires were fulfilled regarding psychological sense of performance capacity and motivation. PRO-CHO and not CHO improved performance in the 4-km run-test (interaction p < .05). An increase in serum creatine kinase was observed during the week, which was greater in CHO than PRO-CHO (interaction p < .01). Lactate dehydrogenase (p < .001) and cortisol (p = .057) increased during the week, but the change did not differ between groups. Reduction in sense of performance capacity during the intervention was greater in CHO (p < .05) than PRO-CHO. In conclusion, ingestion of whey protein hydrolysate before and after each exercise session improves performance and reduces markers of muscle damage during a strenuous 1-week training camp. The results indicate that protein supplementation in conjunction with each exercise session facilitates the recovery from strenuous training in elite orienteers.

Effects of carbohydrate supplementation on competitive runners undergoing overload training followed by a session of intermittent exercise.

This study evaluated the effects of a micro cycle of overload training (1st–8th day) on metabolic and hormonal responses in male runners with or without carbohydrate supplementation and investigated the cumulative effects of this period on a session of intermittent high-intensity running and maximum-performance-test (9th day). The participants were 24 male runners divided into two groups, receiving 61% of their energy intake as CHO (carbohydrate-group) and 54% in the control-group (CON). The testosterone was higher for the CHO than the CON group after the overload training (694.0xa0±xa054.6 vs. CON 610.8xa0±xa047.9xa0pmol/l). On the ninth day participants performed 10xa0×xa0800xa0m at mean 3xa0km velocity. An all-out 1000xa0m running was performed before and after the 10xa0×xa0800xa0m. Before, during, and after this protocol, the runners received solution containing CHO or the CON equivalent. The performance on 800xa0m series did not differ in either group between the first and last series of 800xa0m, but for the all-out 1000xa0m test the performance decrement was lower for CHO group (5.3xa0±xa01.0 vs. 10.6xa0±xa01.3%). The cortisol concentrations were lower in the CHO group in relation to CON group (22.4xa0±xa00.9 vs. 27.6xa0±xa01.4xa0pmol/l) and the IGF1/IGFBP3 ratio increased 12.7% in the CHO group. During recovery, blood glucose concentrations remained higher in the CHO group in comparison with the CON group. It was concluded that CHO supplementation possibly attenuated the suppression of the hypothalamic-pituitary-gonadal axis and resulted in less catabolic stress, and thus improved running performance.

Contraction‐induced changes in skeletal muscle Na+,K+ pump mRNA expression – importance of exercise intensity and Ca2+‐mediated signalling

Aim:u2002 To investigate if exercise intensity and Ca2+ signalling regulate Na+,K+ pump mRNA expression in skeletal muscle.

Skeletal muscle glycogen content and particle size of distinct subcellular localizations in the recovery period after a high-level soccer match

Whole muscle glycogen levels remain low for a prolonged period following a soccer match. The present study was conducted to investigate how this relates to glycogen content and particle size in distinct subcellular localizations. Seven high-level male soccer players had a vastus lateralis muscle biopsy collected immediately after and 24, 48, 72 and 120xa0h after a competitive soccer match. Transmission electron microscopy was used to estimate the subcellular distribution of glycogen and individual particle size. During the first day of recovery, glycogen content increased by ~60% in all subcellular localizations, but during the subsequent second day of recovery glycogen content located within the myofibrils (Intramyofibrillar glycogen, a minor deposition constituting 10–15% of total glycogen) did not increase further compared with an increase in subsarcolemmal glycogen (−7 vs. +25%, respectively, Pxa0=xa00.047). Conversely, from the second to the fifth day of recovery, glycogen content increased (53%) within the myofibrils compared to no change in subsarcolemmal or intermyofibrillar glycogen (Pxa0<xa00.005). Independent of location, increment in particle size preceded increment in number of particles. Intriguingly, average particle size decreased; however, in the period from 3 to 5xa0days after the match. These findings suggest that glycogen storage in skeletal muscle is influenced by subcellular localization-specific mechanisms, which account for an increase in number of glycogen particles located within the myofibrils in the period from 2 to 5xa0days after the soccer match.