ABSTRACT
One hundred drop jumps were performed at maximal intensity every 20 s in 12 untrained subjects (UT), 9 sprinters (S) and 10 long-distance runners (LDR). Muscle contraction force (P20, P50) induced by percutaneous electrical stimulation (20 Hz and 50 Hz, respectively) as well as maximal voluntary contraction force and the height of vertical jumps performed in different ways decreased (P<0.05) and was not restored to the initial value 20 min post exercise. There was a marked increase in low frequency fatigue (LFF) in all the groups studied as substantiated by a significant decrease in the ratio of P20/P50 immediately after exercise as well as 20 min post exercise compared to pre exercise values (P<0.05). However, low frequency fatigue was similar in UT, S and LDR. The jump height of the sprinters during counter-movement jump and drop jump at 90 degrees decreased to a smaller extent compared to jumps performed by LDR and UT. Muscle pain did not differ between UT, S and LDR at 24 h post exercise. The present data indicate that endurance training status as well as prevalence of muscle fibres of the slow type does not decrease muscle resistance to LFF nor accelerate the recovery of muscle contraction force following maximal, intermittent stretch-shortening cycle exercise.
Subject(s)
Exercise/physiology , Muscle Fatigue/physiology , Muscle, Skeletal/physiology , Running/physiology , Adult , Humans , Life Style , Male , Muscle Contraction/physiology , Physical Endurance/physiology , Physical Fitness/physiology , Task Performance and AnalysisABSTRACT
We show that tetraphenylphosphonium inhibits oxidation of palmitoylcarnitine, pyruvate, malate, 2-oxoglutarate and glutamate in heart mitochondria in the range of concentration (1-5 microM) commonly used for the determination of mitochondrial membrane potential. The inhibition of 2-oxoglutarate (but not other substrate) oxidation by tetraphenylphosphonium is dependent on the concentration of 2-oxoglutarate and on extramitochondrial free calcium, and the kinetic plots are consistent with a mixed type of inhibition. Our results indicate that tetraphenylphosphonium interacts with enzymes, specifically involved in the oxidation of 2-oxoglutarate, most possibly, 2-oxoglutarate dehydrogenase.
Subject(s)
Membrane Potentials/drug effects , Mitochondria, Heart/metabolism , Onium Compounds/pharmacology , Organophosphorus Compounds/pharmacology , Oxidative Phosphorylation/drug effects , Animals , Calcium/metabolism , Electron Transport , RatsABSTRACT
The rate and efficiency of energy transport were examined in a system containing isolated rabbit heart mitochondria, hexokinase, adenylate kinase and low concentrations of adenine nucleotides. Oxygen consumption by mitochondria and glucose-6-phosphate synthesis by hexokinase were registered. It was found that when adenylate kinase is active both in mitochondria and in the environmental solution, the rate and efficiency (glucose-6-phosphate/O ratio) of glucose-6-phosphate formation considerably increase. The effects of adenylate kinase activity are fully abolished by diadenosine pentaphosphate, an inhibitor of adenylate kinase.
