I just came across this study in the literature from a couple years ago

Optimizing Altitude for Live High-Train

Low (LHTL) Training

Chapman et al (2013) hypothesized that athletes living at

higher altitudes would experience greater improvements in sea

level performance, secondary to greater hematological acclimatization,

compared to athletes living at lower altitudes. After

4 weeks of group sea level training and testing, 48 collegiate

distance runners (32 men, 16 women) were randomly assigned

to one of four living altitudes (1780m, 2085m, 2454m, or

2800 m). All athletes trained together daily at a common altitude

from 1250m to 3000m following a modified LHTL

model. Subjects completed hematological, metabolic and

performance measures at sea level before and after altitude

training. Upon return from altitude, 3000m time-trial performance

was only significantly improved in groups living at the

middle two altitudes. EPO remained elevated after 72 h except

in the 1780m group. Erythrocyte volume was significantly

higher in all groups but not different between groups. These

data suggest that a 4 week LHTL altitude camp at 2000m to

2500m is optimal for sea level performance.

HIGH ALTITUDE MEDICINE & BIOLOGY

Volume 15, Number 1, 2014

ª Mary Ann Liebert, Inc.

DOI: 10.1089/ham.2014.1513

4

We frequently measure oxygen levels on people of all ages here in our mountain clinics. We order nighttime oximetry and sleep studies and analyze hundreds of data points reflecting heart rate and oxygen levels over time. When we see someone with a low oxygen in clinic, there may be no way of knowing if they have been hypoxic for hours, days, weeks unless they have an illness with an abrupt onset, like influenza or pneumonia or they just returned from sea level. Babies during the first weeks may have low oxygen with no symptoms, since they are accustomed to this in the womb where oxygen saturations run 40-60 %.

A recent article in the Journal of the American Medical Association studied extremely premature babies at 18 months for adverse outcomes including vision, hearing, cognition, motor, and language. They correlated the degree of disability with the length of time the child was hypoxic during the first few months. One minute of hypoxia seemed to be the cut-off. Now this doesn’t tell us how low or how many but it may be a helpful guide when watching someone’s oxygen or analyzing a sleep study. Shorter episodes may be insignificant long term.

This is a complex article and the children with the poorer outcomes had more episodes of hypoxia at older ages- 9-10 weeks after birth. This could mean that the insult to the brain was contributing to the hypoxic episodes as well as the deficits.