The study was designed to determine metabolic and hormonal responses to acute modification of body carbohydrate stores by exercise and subsequent meals and to find out whether the responses depend on the training status of subjects. Nine sedentary students and 10 endurance athletes took part in four experimental sessions. During control session, after overnight fast oxygen uptake and CO2 production were measured and blood glucose, free fatty acids (FFA), insulin (I), leptin (L), growth hormone (GH), testosterone (T), catecholamines, ACTH and cortisol were determined. The remaining sessions were preceded by 1.5 h exercise at 70% HRmax in the evening followed by 12-16 hrs fast till morning when subjects ate either high-carbohydrate (H-CHO) or low-carbohydrate (L-CHO) meal or fasted. Respiratory gases and blood samples were collected before and 2 hours after meal. In glycogen depleted subjects respiratory quotient (RQ), I, norepinephrine (NE) and L decreased, whilst other variables were unaltered. Changes in I and NE were greater in athletes than in sedentary subjects. After H-CHO RQ, blood glucose, I and NE increased and FFA, GH and T decreased. The latter effect was greater in athletes than in untrained subjects. After L-CHO, RQ was at the fasting level and FFA increased only in sedentary group. In both groups I increased and GH and T decreased. Neither meal affected L concentration. In conclusion, hormonal and metabolic changes observed after depleting carbohydrate stores resemble those occurring during starvation. Composition of the ingested meal affects postprandial metabolism, which additionally depends on the subjects’ training status.
Aim of this study was to elucidate the influence of carbohydrate store modification on exercise capacity and catecholamine thresholds. Nine sedentary students and 10 endurance athletes volunteered for the study consisting of four sessions in one-week intervals. During control session (C) subjects performed graded exercise till exhaustion with workload increasing by 50 Watts every 3 min after an overnight fast. Blood lactate and catecholamines were determined at rest, after each workload and at exhaustion. In the evening preceding each of the remaining three sessions subjects performed glycogen reducing exercise lasting 1.5 hrs at 70% HRmax. Till next morning they did not eat any meal but drank water. Two hours before exercise subjects were given either a high-carbohydrate (H-CHO) or a low-carbohydrate (L-CHO) meal of approx. 1000 kcal or remained fasted (F). Depletion of carbohydrate stores enhanced contribution of fat-derived energy substrates at submaximal workloads, but did not influence either maximal oxygen consumption, workload and lactate concentration or lactate threshold. Low carbohydrate availability resulted in elevated concentration of catecholamines only in untrained subjects. Ingestion of a meal either high or low in carbohydrates diminished those changes. Catecholamine thresholds were similar in all sessions and higher in athletes’ group.
The influence of the addition of Potassium Ekosorb to black soil and sandy soil on water content in soils, gas exchange in leaves and yielding of strawberry plants cultivar Senga Sengana, Dukat, Kent and Elsanta was estimated in a field experiment. The obtained results show that the addition of hydrogel increased content of water in both types of soil; however, the effect was on average twice higher in black soil than in sandy soil. The highest stomatal conductance of leaves, photosynthesis and transpiration were observed in plants cultivated in both black and sandy soil with the addition of 3 g dm⁻³ of hydrogel. The addition of higher dose influenced in an ambiguous way on the values of analyzed features of leaves. Yet, regardless of the applied dose of Ekosorb, the stomatal conductance, transpiration and photosynthesis of plants cultivated in black soil were 1.8–2.9 times higher than in sandy soil. The highest yields of fruit on both types of soil were obtained from plants which took advantage of presence of 3 g dm⁻³ of hydrogel. The application of 6 g dm⁻³ influenced on decreasing of plant yields. The weakest reaction on both types of soil occurred in strawberry cultivar Elsanta.
Twelve male, sedentary volunteers (22.0 ± 0.7 yrs) were submitted to three weeks of a bicycle ergometer training, consisting of 45 min exercise (at 70% VO2max), 4 times in the first week and 3 times in the next 2 weeks. They performed four incremental exercise tests with the power output increased by 50 W every 3 min until volitional exhaustion: two before training (C1 and C2), and after one (T1) and three (T3) weeks of training. Before and after each load the plasma noradrenaline (NA), adrenaline (A) and blood lactate (LA) concentrations were determined in venous blood samples as well as plasma growth hormone (HGH) and cortisol concentrations before and at the end of exercise. A decrease in NA concentration was found already after 1 week of training at power output of 100 W (p<0.01) and 200 W (p<0.05). Similar decline was maintained after 3 weeks of training. No significant training-induced differences in plasma A concentration were found, however, the thresholds for both catecholamines were significantly shifted towards higher values after 3 weeks of training. One week of training caused a decrease in the pre-exercise (p<0.01), as well as post-exercise (p<0.05) plasma cortisol and HGH concentrations. It was concluded that endurance training induced a decrease in HGH, cortisol and NA concentration already after one week of training. A decline of pre-exercise plasma HGH and cortisol levels with time of experiment may, in part, indicate familiarization to exercise protocol.