Question

How does the motor unit recruitment pattern described in explain the increase in blood lactate which occurs above 50-60% Vo2max? Blood lactate is the buffered form of lactic acid derived from cellular anaerobic glycolysis. (HINT: connect motor unit recruitment order with collective metabolism. And high/low intensity training

My answer so far: The motor unit recruitment pattern described in the lecture materials tells us that when there is low intensity activity (rest to about 50% of Vo2max), minute ventilation (VE) parallels Vo2. We also learn that onset blood lactate accumulation (OBLA) occurs at about 66% Vo2max, and occurs between 50% and 80% Vo2max.

Answer 1

Motor unit recruitment is the activation of a motor unit if there is increase in contractile strength in muscles during exercise or sports.The skeltal muscle fibers and its motor neuron comprises a motor unit.Activation of more motor neurons activates more motor fibers that increases the contraction of muscles.That means higher the recruitment of motor units higher the strength of muscle contraction.During low intensity work outs the slow twitch motor unit is recruited and as the intensity of work out is increased the fast twitch motor unit is recruited.This also increases the blood lactate levels.There is a threshold value for lactate in blood that can be used up by the muscle fibers.If the lactate concentration in blood increases than it is used up and cannot be removed by the tissues then it is considered to be a threshold value called Anaerobic Threshold.This threshold indicates that lactate production is exceeded in the blood which is called Onset of Blood Lactate(OBLA).This threshold is occured normally when a VO2 max percentage is above or around 66%. Maximal oxygen uptake or VO2 max is the maximum rate of consumption of oxygen when exercising.The threshold value can be increased by increasing the intensity of workout step by step and this is done when endurance is important such as in anaerobic sports events.The blood lactate is formed abouve the threshold value as stated above and this happens when the slow twitch muscles uses mitochondrial respiration or aerobic process to get energy ans as intensity is increased then fast twitch motor unit takes up the work and glycolysis or anaerobic pathway is used as energy source.The end of glycolysis produces pyruvate and this pyruvate is converted to lactate.