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.

BackgroundPurpose of the study was to examine: (1) the criterion validity and test-retest reliability of the IPAQ-LT short-form (SF) and long-form (LF) and (2) its potential over-reporting and energy expenditure over-estimation. Material/Methods130 participants, aged 18 -69 years, wore the Actigraph GT3X accelerometer (ACC) on all waking hours over 7 consecutive days. One day before and after they completed both versions of the back-translated IPAQ-LT. 92 participants were included for the reliability and 81 for the validity tests. Spearman's rho correlation coefficients were calculated as the measurement of agreement. ResultsOnly the walking category significantly (p <.05) correlated with the ACC, SF (.22), LF (.20). Compared with ACC data IPAQ-LT averaged 997% (SF) and 1512% (LF) more weekly minutes of PA and 864% (SF) and 1477% (LF) more MET-min/week. The classification of participants as sufficiently active was 87.6% (SF), 90.1% (LF), and 8.7% (ACC). ConclusionsThe validity for total PA scored relatively low compared with other studies. Substantial PA over-reporting and EE over-estimation were observed. As such, the evidence is very weak to support the use of IPAQ-LT as a relative or an absolute measure of PA and further work in this regard is amended.

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.

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