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Biomedical subjects

B Knechtle

Publications and source records attributed to B Knechtle.

At least 19 recordsLinked to original sources
PubMed2006

[Does running increase the risk of osteoarthritis?].

There is no doubt that the mean body weight of our population is continuously rising. In this context it is interesting to know that running--compared to cycling--results in a higher decrease of subcutaneous adipose tissue and has therefore a favourable influence on body weight. But public opinion still assumes that running provokes arthritis. This is used as a pretext against regular running training. In this overview we would like to show that running does not increase the risk of arthritis contrary to physical inactivity and overweight. Runners do not show a higher risk of developing joint arthritis on their lower extremities. However, frequency of arthritis is significantly higher in inactive and obese persons.

Adolescent↗
PubMed2005

[Changes in body composition during an extreme endurance run].

We measured before, during and after a six-day-run in one athlete body weight, skinfold thickness, circumference of extremities, energy expenditure and nutritional intake. Despite an increased fat and protein intake during the race we found a significantly decrease in adipose subcutaneous tissue of the whole body and muscle mass in the active limbs whereas body weight remained stable. We presume that during running as eccentric exercise subcutaneous adipose tissue and muscle mass will be oxidised.

Adult↗
PubMed2005

Influence of chronic supplementation of arginine aspartate in endurance athletes on performance and substrate metabolism - a randomized, double-blind, placebo-controlled study.

The intake of arginine aspartate has been shown to increase anabolic hormones like human growth hormone (hGH) and glucagon. The aim of our study was to investigate whether daily intake of two different dosages of arginine asparate during four weeks affects selected parameters of overtraining syndrome like performance, metabolic and endocrine parameters. Thirty male endurance-trained athletes were included in a randomized, double-blind, placebo-controlled study and divided into three groups. During four weeks, they ingested either arginine aspartate with a high concentration (H) of 5.7 g arginine and 8.7 g aspartate, with a low concentration (L) of 2.8 g arginine and 2.2 g aspartate or placebo (P).VO(2)peak and time to exhaustion were determined on a cycling ergometer in an incremental exercise test before and after supplementation. Before and after each incremental exercise test, concentrations of hGH, glucagon, testosterone, cortisol, ferritine, lactate, and urea were measured. Compared to placebo, no significant differences on endurance performance (VO(2)peak, time to exhaustion), endocrine (concentration of hGH, glucagon, cortisol, and testosterone) and metabolic parameters (concentration of lactate, ferritine, and urea) were found after chronic arginine aspartate supplementation. The chronic intake of arginine asparate during four weeks by male endurance athletes showed independent of dosage no influence on performance, selected metabolic or endocrine parameters. Consequently, there seems to be no apparent reason why the supplementation of arginine aspartate should be an effective ergogenic aid. The practice of using arginine aspartate as potential ergogenics should be critically reevaluated. Further investigations with higher dosage and extended supplementation periods should be performed.

Adult↗
PubMed2005

Is the intensity of the highest fat oxidation at the lactate concentration of 2 mmol L(-1)? A comparison of two different exercise protocols.

BACKGROUND: The exercise intensity eliciting highest fat oxidation is important for a variety of populations and its precise determination requires an adequate exercise protocol. The aim of this study was to compare fat oxidation, concentration of lactate and lactate threshold during an established exercise protocol using fixed workloads with a protocol based upon the subject's individual heart rate response to exercise. MATERIALS AND METHODS: Highest fat oxidation, concentration of lactate and lactate threshold were compared between two different exercise protocols in moderately trained men (n = 48) and women (n = 30). In randomized order subjects completed a standardized (STAND) and an individual (IND) submaximal exercise test. The increments during IND were adapted by the subjects' individual heart rate response to exercise compared to STAND with defined steps. RESULTS: In men, fat oxidation was significantly higher at the intensity eliciting highest fat oxidation in STAND than in IND (P = 0.019), but not in women. In both genders lactate concentration (P < 0.001) and heart rate (HR) (P < 0.001) were significantly higher in IND compared to STAND at this intensity. A significant correlation between O2 at lactate threshold and the intensity eliciting the highest fat oxidation was found in both genders in IND (women r = 0.73; men r = 0.43) and in STAND (women r = 0.57; men r = 0.56). CONCLUSION: Different exercise increments and stage durations have an influence on lactate concentration and HR at the intensity eliciting the highest fat oxidation. The shorter test duration of STAND favours this protocol to determine maximal fat oxidation. For the untrained, start of exercise should be at very low intensity.

Adult↗
PubMed2004

[Influence of physical activity on mental well-being and psychiatric disorders].

It has been shown that endurance as well as resistance training improves mental well-being in the athlete. In patients with psychiatric disorders, physical exercise diminishes clinical symptoms. Especially in patients with depression, endurance exercise improves mood. Physical training has to be integrated in a concept due to the fact the physical exercise can not replace medicinal therapy. It has to be postulated that improved mood is a result of increased endogenous opioids.

Adolescent↗
PubMed2004

[Energy turnover in endurance exercise].

During endurance exercise energy derives mainly from oxidation of carbohydrates and fat. Carbohydrates are stored in muscle and liver glycogen, fat is stored in adipose subcutaneous tissue and in intramuscular triglycerides. The intramuscular stores are the preliminary sources of fuel during muscular exercise. The principles of fatloading and carboloading are useful in increasing the intramuscular stores before exercise. The increased muscular reserves enable the athlete to maintain a higher intensity for longer time. During exercise depletion of glycogen may be delayed by ingestion of carbohydrates. Due to the limited resorption and oxidation of carbohydrates, efficacy of ingested carbohydrates is clearly limited. Due to the limitation in energy stores in the muscles and the limitation of energy ingestion during exercise, a considerable energy deficiency in long lasting events over days has to be considered.

Energy Metabolism↗
PubMed2004

Fat oxidation at different intensities in wheelchair racing.

STUDY DESIGN: Determination of fat oxidation at three different intensities in trained wheelchair athletes on the treadmill. OBJECTIVE: The aim of the study was to assess the level and highest rate of fat oxidation in endurance-trained wheelchair athletes for recommendation on endurance training. SETTING: Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland. METHODS: Nine (seven men and two women) endurance-trained wheelchair athletes (VO(2peak) 40.2+/-6.7 ml/kg/min) were studied over 20 min at 55, 65 and 75% VO(2peak) on a treadmill in their own racing wheelchairs in order to find the exercise intensity with the highest absolute fat oxidation. RESULTS: As presumed, total energy expenditure for wheelchair racing was highest at 75% VO(2peak), while absolute fat oxidation was statistically not significantly different at the three tested intensities. Percentage of energy expenditure from fat oxidation decreased with increasing intensity from 31.4% at 55% VO(2peak) to 20.9% at 75% VO(2peak), while percentage from carbohydrate oxidation increased from 68.6% at 55% VO(2peak) to 79.1% at 75% VO(2peak). CONCLUSION: For wheelchair athletes, we recommend training of fat metabolism for endurance exercise at an intensity of 55% VO(2peak), because absolute fat metabolism is not higher at higher intensities but less carbohydrates are used at lower intensity levels. At lower intensities, exercise can be performed over a longer time before the emptied glycogen stores will limit exercise duration. This may apply especially to paraplegic subjects whose active muscle mass is limited in contrast to able-bodied athletes.

Adult↗
PubMed2004

Optimal exercise intensities for fat metabolism in handbike cycling and cycling.

STUDY DESIGN: Energy expenditure (EE) and fat oxidation in handbike cycling compared to cycling in order to determine the intensity that elicits maximal fat oxidation in handbike cycling. OBJECTIVE: To establish the exercise intensity with the highest fat oxidation rate in handbike cycling compared with cycling (control group) in order to give training recommendations for spinal cord-injured (SCI) athletes performing handbike cycling. SETTING: Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland. METHODS: Eight endurance-trained handbike cyclists (VO2 peak(handbike cycling) 37.5+/-7.8 ml/kg/min) and eight endurance trained cyclists (VO2 peak(cycling) 62.5+/-4.5 ml/kg/min) performed three 20-min exercise blocks at 55, 65 and 75% VO2 peak in handbike cycling on a treadmill or in cycling on a cycling ergometer, respectively, in order to find the intensity with the absolutely highest fat oxidation. RESULTS: The contribution of fat to total EE was highest (39.1+/-16.3% EE) at 55% VO2 peak in handbike cycling compared to cycling, where highest contribution of fat to EE (50.8+/-13.8%) was found at 75% VO2 peak. In handbike cycling, the highest absolute fat oxidation (0.28+/-0.10 g/min) was found at 55% VO2 peak compared to cycling, where highest fat oxidation (0.67+/-0.20 g/min) was found at 75% VO2 peak. CONCLUSION: Well-trained handbike cyclists have their highest fat oxidation at 55% VO2 peak(handbike cycling) compared to well-trained cyclists at 75% VO2 peak(cycling). Handbike cyclists should perform endurance exercise training at 55% VO2 peak(handbike cycling), whereas well-trained cyclists should be able to exercise at 75% VO2 peak(cycling). For training recommendations, the heart rate at 55% VO2 peak(handbike cycling) lies at 135+/-6 bpm in handbike cycling in SCI compared to 147+/-14 bpm at 75% VO2 peak(cycling) in well-trained cyclists. We presume that the reduced muscle mass involved in exercise during handbike cycling is the most important factor for impaired fat oxidation compared to cycling. But also other factors as fitness level and haemodynamic differences should be considered. Our results are only applicable to well-trained handbike cyclists with SCI and not for the general SCI population.

Adult↗
PubMed2004

Fat oxidation in men and women endurance athletes in running and cycling.

Recent studies showed that the maximal fat oxidation seems to be different in men and women and that it can be influenced by type and intensity of exercise. Nineteen endurance trained male (V.O (2)peak 61.3 +/- 4.4 ml x kg (-1) x min (-1)) and 17 female (V.O (2)peak 52.8 +/- 4.5 ml x kg (-1) x min (-1)) athletes were studied over 30 min at 55, 65 and 75 % V.O (2)peak on a treadmill and a cycling ergometer in order to find the intensity and kind of exercise with the highest absolute fat oxidation. For women, normalised (per body weight) fat oxidation was higher at 75 % V.O (2)peak than at 55 % V.O (2)peak for both running (p = 0.02) and cycling (p = 0.01). Women also oxidised a significantly higher percentage of fat with regard to total energy expenditure than men in running (p = 0.02) and cycling (p = 0.004). Normalised carbohydrate oxidation was significantly higher for men at each tested intensity (p < 0.05) and compared to kind of exercise in men (p = 0.006) and women (p = 0.002) in cycling than in running. Men and women showed a significantly higher normalised fat oxidation for running compared to cycling (p = 0.01). Cycling produced in men (p = 0.06) and women (p = 0.001) significantly more lactate than running. In summary, we found at 75 % V.O (2)peak a higher fat oxidation rate than at 65 % V.O (2)peak and 55 % V.O (2)peak for men and women in cycling and running. This is coincident with lactate threshold in men and women in cycling but not in running, where lactate threshold is higher than 75 % V.O (2)peak.

Adult↗
PubMed2003

[Energy metabolism in long-term endurance sports: a case study].

During the Swiss Citypower Gigathlon 2002, we determined energy turnover in one athlete. The average intake of calories was at 6500 calories per day and a deficit of 3500 calories per day resulted. This was due to the energy expenditure of about 10,000 calories per day. We concluded that it is extremely difficult or rather impossible to cover the total energy expenditure by nutrition during extreme events.

Adult↗
PubMed2003

Evaluation of sprint exercise testing protocols in wheelchair athletes.

STUDY DESIGN: Comparison of five different exercise testing protocols with different speeds on a treadmill with seven wheelchair athletes. OBJECTIVE: To determine which speed and duration in an exercise protocol is best to test wheelchair athletes performing sprint races on a track. SETTING: Swiss Paraplegic Centre, Nottwil, Switzerland. METHODS: Three elite and four junior wheelchair athletes (18.7+/-6.8 years, 52.1+/-9.7 kg and 165.3+/-19.3 cm) performed five different exercise testing protocols at different speeds on a treadmill until exhaustion. Maximal effort treadmill (0.7% incline) testing protocols were performed using three timeframes. The first was focussing on short duration tests (S1 and S2) where incremental increases in velocity (0.42 and 0.1 m.s(-1)) were required from a stationary start. The second were medium duration tests (M1 and M2) where the athlete started at their 200 m and 800 m personal best time (mean velocities) and then had the velocity increased 1 km.h(-1) by every 10 and 60 s respectively. The long duration test (L) started at 14 km.h(-1) and velocity was increased by 2 km.h(-1) every 120 s. Maximal heart rate, maximal concentration of lactate, maximal speed, and maximal duration of the test were measured. RESULTS: The highest concentration of lactate and the highest heart rates were measured in the longest tests. CONCLUSION: During maximal effort testing wheelchair athletes are able to produce higher lactate concentrations when tested for longer duration. Post test lactate assessments provide little information in short duration testing protocols. Sequential lactate assessments post-test may provide additional information on the rate of recovery for middle distance wheelchair athletes and warrants further investigation.

Adolescent↗
PubMed2003

Effects of different sodium concentrations in replacement fluids during prolonged exercise in women.

OBJECTIVE: To investigate the effect of different sodium concentrations in replacement fluids on haematological variables and endurance performance during prolonged exercise. METHODS: Thirteen female endurance athletes completed three four hour runs on a 400 m track. Environmental conditions differed between the three trials: 5.3 degrees C and snow (trial 1), 19.0 degrees C and sunny weather (trial 2), 13.9 degrees C and precipitation (trial 3). They consumed 1 litre of fluid an hour during the trials with randomised intake of fluids: one trial (H) with high sodium concentration (680 mg/l), one trial (L) with low sodium concentration (410 mg/l), and one trial with only water (W). Before and after the trials, subjects were weighed and blood samples were taken for analysis of [Na(+)](plasma), packed cell volume, and mean corpuscular volume. RESULTS: The mean (SD) decrease in [Na(+)](plasma) over the whole trial was significantly (p<0.001) less in trial H (2.5 (2.5) mmol/l) than in trial W (6.2 (2.1) mmol/l). Mild hyponatraemia ([Na(+)](plasma) = 130-135 mmol/l) was observed in only six women (46%) in trial H compared with nine (69%) in trial L, and 12 (92%) in trial W. Two subjects (17%) in trial W developed severe hyponatraemia ([Na(+)](plasma)<130 mmol/l). No significant differences were found in performance or haematological variables with the three different fluids. There was no significant correlation between[Na(+)](plasma) after the run and performance. There was a significant correlation between changes in [Na(+)](plasma) and changes in body weight. CONCLUSIONS: Exercise induced hyponatraemia in women is likely to develop from fluid overload during prolonged exercise. This can be minimised by the use of replacement fluids of high sodium concentration. Sodium replacement of at least 680 mg/h is recommended for women in a state of fluid overload during endurance exercise of four hours. However, higher [Na(+)](plasma) after the run and smaller decreases in [Na(+)](plasma) during the trials were no indication of better performance over four hours.

Adult↗
PubMed2002

[Exercise intensity and fat burning--theoretical principles and practical considerations].

There are several methods to eliminate unnecessary subcutaneous adipose tissue. Aerobic exercise seems to be the cheapest and most efficient method compared to diets, pills or even surgery. Subcutaneous adipose tissue can only be reduced by lipolysis and oxidation in the working muscles. The intensity of exercise is the most relevant factor in fat oxidation. Even though fat oxidation is highest at low to moderate intensities, well trained athletes have their highest fat oxidation at the ventilatory threshold. Therefore, different intensities for trained compared to untrained persons have to be recommended in order to burn fat. The determination of concentrations of lactate seems to be of important practical use.

Adipose Tissue↗
PubMed2001

Treadmill exercise testing with increasing inclination as exercise protocol for wheelchair athletes.

STUDY DESIGN: Treadmill testing on a progressive incline of 11 wheelchair athletes. OBJECTIVE: To determine if a novel treadmill exercise protocol which uses increments in inclination, rather than the standard increments in velocity, can be used to effectively determine maximum oxygen uptake VO2max for elite wheelchair athletes. SETTING: Nottwil, Switzerland. METHODS: Eleven elite wheelchair basketball players (29.3+/-6.3 years, 72.7+/-16.9 kg and 177+/-9.6 cm) performed an exercise protocol with increasing inclination on the treadmill. Eight players had a spinal cord injury (SCI), two had no lesion of the central nervous system and one had poliomyelitis. VO2max and heart rate were measured continuously, while serum lactate was determined immediately after the exercise protocol. RESULTS: Athletes reached a maximal heart rate of 185+/-11.4 bpm and maximal lactate of 10.2+/-2.1 mmol/l. VO2max was 35.1+/-4.9 ml/min/kg. The correlation between heart rate and VO(2) at different inclinations was statistically significant and comparable to able-bodied subjects. CONCLUSIONS: An exercise protocol with increasing inclination is a valid alternative to an exercise protocol with increasing velocity.

Adult↗
PubMed2000

[Nutrition in long physical endurance events].

In recent years, there was a trend towards longlasting endurance events. The longer the competitions last, the more important nutrition and fluid replacement will be before, during, and after a race, because an inadequate supply reduces performance. Therefore, we summarize in this review the importance of carbohydrate and fat as well as the substitution of water and electrolytes concerning races of more than 4 hours duration.

Adult↗
PubMed1998

[Status febrilis and jaundice].

A 49 year old patient was admitted with fever and jaundice. Laboratory evaluation showed leukocytosis, elevated values for C-reactive protein, transaminases, bilirubin and alkaline phosphatase. Ultrasound and subsequent CT-scan revealed multiple liver lesions and a liquid mass in the bursa omentalis. A CT-guided catheter-drainage was performed and streptococcus milleri isolated from the abscess and one blood culture. After empiric broad spectrum treatment with Piperacillin/Tazobactam (Tazobac) and Netilmicin (Netromycin), Ceftriaxon (Rocephin) was given for a total treatment time of 10 days. Further evaluation revealed a perforated peptic ulcer as possible etiology for the described localized infectious complication.

Abdominal Abscess↗