PubMed Health⌕ Search

Biomedical subjects

Monica Zehnder

Publications and source records attributed to Monica Zehnder.

5 recordsLinked to original sources
PubMed2006

Intramyocellular lipid stores increase markedly in athletes after 1.5 days lipid supplementation and are utilized during exercise in proportion to their content.

Intramyocellular lipids (IMCL) and muscle glycogen provide local energy during exercise (EX). The objective of this study was to clarify the role of high versus low IMCL levels at equal initial muscle glycogen on fuel selection during EX. After 3 h of depleting exercise, 11 endurance-trained males consumed in a crossover design a high-carbohydrate (7 g kg(-1) day(-1)) low-fat (0.5 g kg(-1) day(-1)) diet (HC) for 2.5 days or the same diet with 3 g kg(-1) day(-1) more fat provided during the last 1.5 days of diet (four meals; HCF). Respiratory exchange, thigh muscle substrate breakdown by magnetic resonance spectroscopy, and plasma FFA oxidation ([1-(13)C]palmitate) were measured during EX (3 h, 50% W (max)). Pre-EX IMCL concentrations were 55% higher after HCF. IMCL utilization during EX in HCF was threefold greater compared with HC (P < 0.001) and was correlated with aerobic power and highly correlated (P < 0.001) with initial content. Glycogen values and decrements during EX were similar. Whole-body fat oxidation (Fat(ox)) was similar overall and plasma FFA oxidation smaller (P < 0.05) during the first EX hour after HCF. Myocellular fuels contributed 8% more to whole-body energy demands after HCF (P < 0.05) due to IMCL breakdown (27% Fat(ox)). After EX, when both IMCL and glycogen concentrations were again similar across trials, a simulated 20-km time-trial showed no difference in performance between diets. In conclusion, IMCL concentrations can be increased during a glycogen loading diet by consuming additional fat for the last 1.5 days. During subsequent exercise, IMCL decrease in proportion to their initial content, partly in exchange for peripheral fatty acids.

Adult↗
PubMed2006

The effect of increased lipid intake on hormonal responses during aerobic exercise in endurance-trained men.

In view of the growing health problem associated with obesity, clarification of the regulation of energy homeostasis is important. Peripheral signals, such as ghrelin and leptin, have been shown to influence energy homeostasis. Nutrients and physical exercise, in turn, influence hormone levels. Data on the hormonal response to physical exercise (standardized negative energy balance) after high-fat (HF) or low-fat (LF) diet with identical carbohydrate intake are currently not available. The aim of the study was to investigate whether a short-term dietary intervention with HF and LF affects ghrelin and leptin levels and their modulators, GH, insulin and cortisol, before and during aerobic exercise. Eleven healthy, endurance-trained male athletes (W(max) 365 +/- 29 W) were investigated twice in a randomized crossover design following two types of diet: 1. LF - 0.5 g fat/kg body weight (BW) per day for 2.5 days; 2. HF - 0.5 g fat/kg BW per day for 1 day followed by 3.5 g fat/kg BW per day for 1.5 days. After a standardized carbohydrate snack in the morning, metabolites and hormones (GH, ghrelin, leptin, insulin and cortisol) were measured before and at regular intervals throughout a 3-h aerobic exercise test on a cycloergometer at 50% of W(max). Diet did not significantly affect GH and cortisol concentrations during exercise but resulted in a significant increase in ghrelin and decrease in leptin concentrations after LF compared with HF diet (area under the curve (AUC) ghrelin LF vs HF: P < 0.03; AUC leptin LF vs HF: P < 0.02, Wilcoxon rank test). These data suggest that acute negative energy balance induced by exercise elicits a hormonal response with opposite changes of ghrelin and leptin. In addition, the hormonal response is modulated by the preceding intake of fat.

Adult↗
PubMed2005

Gender-specific usage of intramyocellular lipids and glycogen during exercise.

PURPOSE: Gender-specific differences in substrate utilization during exercise have been reported, typically such that women rely more on fat than men. This study investigated whether gender differences exist in the utilization of intramyocellular lipids (IMCL) and glycogen. METHODS: IMCL and glycogen, as well as total fat and carbohydrate (CHO) oxidation were measured in nine males and nine females before, during, and after an endurance exercise. The trained subjects exercised on a bicycle ergometer at 50% maximal workload for 3 h. IMCL and glycogen were determined in the thigh by magnetic resonance spectroscopy. Oxygen uptake (VO(2)) and carbon dioxide production were determined by open circuit spirometry to calculate total fat and CHO oxidation. Relative power output, percent of maximum heart rate, VO(2peak), and respiratory exchange ratio were the same. RESULTS: Average fat oxidation was the same, whereas CHO oxidation was significantly higher in males compared with females. The relative contribution of these fuels to total energy used were similar in males and females. Males and females depleted IMCL and glycogen significantly (P < 0.001) during the 3-h exercise. IMCL levels at rest (P < 0.05) and its depletion during exercise (P < 0.001) were significantly higher in males compared with females, whereas glycogen was stored and used in the same range by both genders. CONCLUSION: During this 3-h exercise, energy supplies from fat and CHO were similar in both genders, and males as well as females reduced their IMCL stores significantly. The larger contribution of IMCL during exercise in males compared with females could either be a result of gender-specific substrate selection, or different long-term training habit.

Adult↗
PubMed2004

Further glycogen decrease during early recovery after eccentric exercise despite a high carbohydrate intake.

BACKGROUND: Delayed onset muscle soreness (DOMS) is a well-known phenomenon of athletes. It has been reported from muscle biopsies that the rate of muscle glycogen resynthesis is reduced after eccentric compared to concentric exercise. AIM OF THE STUDY: Try to compensate by a carbohydrate (CHO)-rich diet the decelerated glycogen resynthesis after eccentric exercise, measured by magnetic resonance spectroscopy. METHODS: Glycogen, phosphocreatine, ATP, and Pi were measured in the human calf muscle. Twenty athletes divided into two groups (DOMS and CONTROL), reduced glycogen in M. gastrocnemius during two different running protocols. Additionally, 12 DOMS subjects performed an eccentric exercise while the CONTROL group rested. Subsequently, subjects consumed a CHO-rich diet (> 10 g/kg body mass/24 h). RESULTS: In both groups, glycogen has been reduced by about 50%. The first 2 h after exercise, glycogen dropped further (-15.6 +/- 15.7 mmol/ kg ww) in the DOMS but rose by +18.4 +/- 20.8 mmol/kg ww in the CONTROL group (P < 0.001). CONTROL subjects reached resting glycogen within 24 h (137 +/- 47 mmol/kg ww), while DOMS subjects needed more than one day (91 +/- 23 mmol/kg ww; P < 0.001). Pi and Pi/PCr, indicators of muscle injury, rose significantly in the DOMS but not in the CONTROL group. CONCLUSION: The diet rich in CHO's was not able to refill glycogen stores after eccentric exercise. Glycogen decreased even further during the beginning of recovery. This loss, which to our knowledge has not been measured before is probably the consequence of muscle cell damage and their reparation.

Adult↗