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Visa fullständig version : Anaerob energiförbrukning och mekanisk effektivitet vid benpress till utmattning


King Grub
2010-10-27, 09:27
Information about anaerobic energy production and mechanical efficiency that occurs over time during short-lasting maximal exercise is scarce and controversial. Bilateral leg press is an interesting muscle contraction model to estimate anaerobic energy production and mechanical efficiency during maximal exercise because it largely differs from the models used until now. This study examined the changes in muscle metabolite concentration and power output production during the first and the second half of a set of 10 repetitions to failure (10RM) of bilateral leg press exercise. On two separate days, muscle biopsies were obtained from vastus lateralis prior and immediately after a set of 5 or a set of 10 repetitions. During the second set of 5 repetitions, mean power production decreased by 19% and the average ATP utilisation accounted for by phosphagen decreased from 54% to 19%, whereas ATP utilisation from anaerobic glycolysis increased from 46 to 81%. Changes in contraction time and power output were correlated to the changes in muscle Phosphocreatine (PCr; r = -0.76; P<0.01) and lactate (r = -0.91; P<0.01), respectively, and were accompanied by parallel decreases (P<0.01-0.05) in muscle energy charge (0.6%), muscle ATP/ADP (8%) and ATP/AMP (19%) ratios, as well as by increases in ADP content (7%). The estimated average rate of ATP utilisation from anaerobic sources during the final 5 repetitions fell to 83% whereas total anaerobic ATP production increased by 9% due to a 30% longer average duration of exercise (18.4±4.0 vs 14.2±2.1 s). These data indicate that during a set of 10RM of bilateral leg press exercise there is a decrease in power output which is associated with a decrease in the contribution of PCr and/or an increase in muscle lactate. The higher energy cost per repetition during the second 5 repetitions is suggestive of decreased mechanical efficiency.

PLoS One. 2010 Oct 19;5(10):e13486. Anaerobic Energy Expenditure and Mechanical Efficiency during Exhaustive Leg Press Exercise.

Mauritz Jönsson
2010-10-27, 09:42
Intressant information!

Tack min käre kollega!

/Mauritz

Gefan
2010-10-27, 13:26
Försökte förstå vad som stod i texten, men det gick inte så bra. Googlade lite och det verkade vara något med mjölksyran? Kan någon förklara bättre? :)

hejhopp79
2010-10-27, 18:34
Försökte förstå vad som stod i texten, men det gick inte så bra. Googlade lite och det verkade vara något med mjölksyran? Kan någon förklara bättre? :)

Bilateral i sammanhanget betyder helt enkelt att du använder båda benen samtidigt, d v s en "vanlig" benpress-övning. Motsatsen skulle vara att använda ett ben i taget.

Man testade alltså den första och andra halvan av 10 reps i en benpress-övning, d v s de första 5 reps och de sista 5 reps av 10 stycken. På olika dagar dessutom. Resultaten visar att PCr sänktes under de sista 5 repetitionerna vilket författarna menar tyder på "decreased mechanical efficiency."

Som jag tolkar det, använder de första fem repsen PCr och de sista fem glykogen i musklerna? Kanske är jag ute och cyklar. Energianvändningen ändras alltså från 1-5 reps till 6-10 reps. Dessutom är energiåtgången högre under de sista 5 repetitionerna vilket innebär återigen "decreased mechanical efficiency." Vad nu det exakt innebär i sammanhanget?

This study examined the changes in muscle metabolite concentration and power output production during the first and the second half of a set of 10 repetitions to failure (10RM) of bilateral leg press exercise.

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hese data indicate that during a set of 10RM of bilateral leg press exercise there is a decrease in power output which is associated with a decrease in the contribution of PCr and/or an increase in muscle lactate. The higher energy cost per repetition during the second 5 repetitions is suggestive of decreased mechanical efficiency.