Regular consumption of fruits and vegetables (FV) is widely regarded as an important contributor to a healthy diet. Inadequate consumption of plant foods is associated with an inadequate supply of important micronutrients like vitamins, phytochemicals and minerals. In athletes a deficit of these micronutrients can lead to excessive production of reactive oxygen and nitrogen species that induce tissue damage, a higher frequency of inflammatory processes, decreased immunity, increased susceptibility to injury, and prolonged recovery. But many athletes rarely achieve the recommended intake of FV due to difficult coordination of training activities and food intake, or due to problems with digestion of FV. Therefore, in recent years more and more sports people have adopted supplemental FV concentrates to work around timing problems with uptake and the detrimental digestive effects during training of high FV intake. It is thought that supplementation of an athlete’s basic diet with mixed FV concentrates can promote stable health and immunity, in order to provide a basis for optimal adaptation and performance. The intention of this article is to build a bridge between the science behind FV supplementation in exercise on the one hand and the practical relevance of its application on the other. For that purpose this paper addresses three questions: Is supplementation with a mixed FV concentrate to the athlete’s diet appropriate to ensure stable health and immunity? Can supplementation with a mixed FV concentrate improve performance? Counseling guidance: how can sport nutrition advisors decide whether or not to supplement with mixed FV concentrates?
Dienstag, 2. Juli 2013
Science: Direct and indirect lactate oxidation in trained and untrained men
Lactate has been shown to be an important oxidative fuel. We aimed to quantify total lactate oxidation rate (Rox) and its direct versus indirect (glucose that is gluconeogenically derived from lactate and subsequently oxidized) components (mg·kg(-1)·min(-1)) during rest and exercise in humans. We also investigated the effects of endurance training, exercise intensity, and blood lactate concentration ([lactate]b) on direct and indirect lactate oxidation. Six untrained (UT) and six trained (T) men completed 60 min of constant load exercise at power outputs (PO) corresponding to their lactate threshold (LT). Trained subjects completed two additional 60-min sessions of constant load exercise at 10% below the LT workload (LT-10%), one of which included a lactate clamp (LT-10%+LC). Rox was higher at LT in T (22.7 ± 2.9, 75% VO2peak) compared to UT (13.4 ± 2.5, 68% VO2peak, P < 0.05). Increasing [lactate]b (LT-10%+LC, 67% VO2peak) significantly increased lactate Rox (27.9 ± 3.0) compared to its corresponding LT-10% control (15.9 ± 2.2, P < 0.05). Direct and indirect lactate oxidation rates increased significantly from rest to exercise and their relative partitioning remained relatively constant in all trials, but differed between T and UT: direct oxidation comprised 75% of total lactate oxidation in UT and 90% in T suggesting the presence of training-induced adaptations. Partitioning of total carbohydrate (CHO) utilization showed that subjects derived one-third of CHO energy from blood lactate, and exogenous lactate infusion significantly increased lactate oxidation, causing a glycogen sparing effect in exercising muscle.
Standort:
Berkeley, Kalifornien, USA
Labels:
CA Emhoff,
GA Brooks,
JA Fattor,
LA Messonnier,
MA Horning,
TJ Carlson
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