Subject: RE: LT HR compared to Aerobic threshold HR In my (non-professional ) experience, you'll see different definitions of these terms in different places. For example, some will say that LT is the point at which lactic acid concnetration in the blood begins to increase. Others say that LT is the point at which it becomes 4 mmoL/l. Still others call the latter OBLA. And others instead call the latter anaerobic threshold. The term 'ventilatory threshold' also gets thrown around in this context -- one by-product of lactic acid 'clearing' is CO2, which is expelled by breathing, so when CO2 production goes up, respiration increases, and I've seen 'ventilatory threshhold' used to describe the point at which this occurs. I've read things that suggest that there is an order to these events: first LT occurs (lactic acid concentratin begins to increase ); then you hit AT (4 mmoL/l ), at which point, supposedly, anaerobic energy streams -- especially anaerobic glycosis -- become important; then you hit VT (to expel the CO2 that results from converting lactic acid to lactate, which is then used as energy, causing the release of CO2 ). I don't think there is any significant practical upshot. From what I've read, even if you care to make these distinctions, the differences in HR are less than the error involved in measuring them. Edited by Experior 2009-04-09 7:33 AM
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