Skeletal muscle and cerebral oxygenation levels during and after submaximal concentric and eccentric isokinetic exercise.

The aim was to investigate the potential differences in muscle (vastus lateralis) and cerebral (prefrontal cortex) oxygenation levels as well as in the number of repetitions and total work output between isokinetic eccentric and concentric exercise at a moderate relative intensity until exhaustion. Ten recreationally active young men underwent two isokinetic exercise sessions either concentric or eccentric, one on each randomly selected leg. The protocols were performed at 60°/s and an intensity corresponding to 60% of the maximal voluntary contraction (MVC) of each contraction type. Concentric torque was significantly lower compared to eccentric torque in both peak values and at values corresponding to 60% of MVC [230 ± 18 Nm vs. 276 ± 19 Nm (P = .014) and 137 ± 12 Nm vs. 168 ± 11 Nm, respectively (P = .010)]. The participants performed 40% more contractions during eccentric compared to concentric exercise [122 ± 15 vs. 78 ± 7, respectively]. No differences were found in the levels of oxyhaemoglobin, deoxyhemoglobin, total haemoglobin and tissue saturation index when eccentric and eccentric exercise regimes were compared (all P > .05). Our results demonstrate that eccentric exercise of moderate intensity leads to greater resistance to fatigue and more work output compared to concentric exercise, despite the comparable muscle and cerebral oxygenation levels.

Dietary Cysteine Intake is Associated with Blood Glutathione Levels and Isometric Strength.

Glutathione is the most abundant cellular antioxidant and regulates redox homeostasis. Healthy individuals with certain antioxidant inadequacies/deficiencies exhibit impairments in physiological functions. The aim was to investigate whether low levels of dietary cysteine intake are associated with a) lower erythrocyte glutathione, b) increased plasma F2-isoprostanes, and c) impaired muscle function. Towards this aim, we recorded the dietary intake of the three amino acids that synthesize glutathione (i. e., glutamic acid, cysteine, and glycine) in forty-one healthy individuals, and subsequently measured erythrocyte glutathione levels. Maximal isometric strength and fatigue index were also assessed using an electronic handgrip dynamometer. Our findings indicate that dietary cysteine intake was positively correlated with glutathione levels (r=0.765, p<0.001). In addition, glutathione levels were negatively correlated with F2-isoprostanes (r=- 0.311, p=0.048). An interesting finding was that glutathione levels and cysteine intake were positively correlated with maximal handgrip strength (r=0.416, p=0.007 and r=0.343, p=0.028, respectively). In conclusion, glutathione concentration is associated with cysteine intake, while adequate cysteine levels were important for optimal redox status and muscle function. This highlights the importance of proper nutritional intake and biochemical screening with the goal of personalized nutrition.

Priming exercise increases Wingate cycling peak power output.

PURPOSE: The aim of the present study was to investigate the effect of priming exercise on Wingate performance and fatigue. METHODS: Twelve recreationally active young male volunteers participated in the study (age: 25 ± 5 years; weight: 75.0 ± 7.5 kg; height: 177 ± 6 cm; BMI: 24.0 ± 1.7). During a first visit, participants performed a typical V˙O2max test and a supramaximal assessment of V˙O2max on a cycle ergometer, while during the next three visits, the participants performed in a random order a Wingate test (i) with no priming exercise, (ii) after priming exercise followed by a 15-min recovery (Priming15) and (iii) after priming exercise followed by a 30-min recovery (Priming30). Priming exercise lasted 6 min, at work rate corresponding to the gas exchange threshold (GET) plus 70% of the difference between the GET and V˙O2max. RESULTS: The Priming 30 condition exhibited greater peak power output (595 ± 84 W) compared to the control (567 ± 85 W) and the Priming15 condition (569 ± 95 W) (P < .05). Regarding fatigue index, a tendency towards increased resistance to fatigue was observed in the Priming30 condition compared to the control and the Priming15 conditions (P = .072). Pre-Wingate lactate levels were found to be significantly different between the Priming15 (7.18 ± 3.09 mmol/L) and the Priming30 (4.87 ± 2.11 mmol/L) conditions (P < .05). CONCLUSIONS: Priming exercise of high intensity followed by a prolonged recovery leads to increased peak power in a subsequent Wingate test. Moreover, our data are consistent with the idea that a priming exercise-induced modest increase in blood lactate concentration at the onset of the following criterion bout is a key factor of performance.