hi,
I’ve read a very interesting article about LT1, the base for an appropriate polarized training approach.
80% of HRmax will be higher than HR at LT1 in untrained subjects, but will be lower in the advanced. In addition, HR at LT1 corresponded tot 77 and 86% of HRmax in the least and the best trained, respectively. In an often-cited study, Achten et al (2002) found that fat oxidation was maximal (FATmax) between 68 and 79% of HRmax in 18 moderately trained male cyclists. This publication alone suggests that staying below 80% of HRmax will do for BE training.
The present data also show that both lactate thresholds come closer to each other with increasing training status: LT1 and LT2 were only 29 Watt (9%) or 10 bpm separated from each other in the fittest subjects. Hence, the difference between producing no lactate at all and a lot of lactate is very small in well-trained men, and this is an additional reason to be careful with training at intensities close to LT1, apart from the fact that systematic training at such relatively high workloads (LT1 = 252 Watt when maximal power = 314 Watt) costs a lot of energy.