Improved Capacity

My last post involved me introducing the benefits of interval training and how to properly incorporate interval training to suit your needs.  Today, I want to share some of the recent improvements I have made in my running speed.  I conducted the exact same interval session as I had done in a previous workout (Work:Recovery - 5min:5min; 8.0mph:9.5mph), and this is the end result:

What should be noted is the total duration, duration of intervals, and heart rate during intervals.  For starters, I was able to maintain during intervals for 75 minutes, which is considerably longer than my previous bout of 53 minutes.  Secondly, my duration during intervals were the FULL 5 minutes which contrasted with the previous attempt.  In the before graph, you can see that interval 2 and 3 seem shorter than 5 minutes as they are. I was unable to maintain speed.  Finally, my heart rate during intervals and during recovery was less during my recent bout illustrating cardiovascular adaptation and improved performance. 

What does this mean? Theoretically I have the potential for a greater work output at similar heart rates in comparison to previous attempts.  Intervals do improve performance, but I cannot give my training all the credit...

These past 4 days I have been "acclimating" which means physiological changes that occur through artificially produced environments.   My acclimation has been taking place in an insulated chamber set to 33 degrees Celcius and 60-70% humidity.  I am to workout in this sweat box for 1 hour and 40 minutes at a demanding work rate to increase core temperature.  What is a demanding work rate in the sweat box? For me it was on average 120-130 watts on an upright cycle ergometer which is considerably less than when I am in a normal climate. So why does acclimation warrant the improvements in my intervals? Here is a table outlining the benefits and consequences of  acclimation (Armstrong & Maresh, 1991):

As you can see, the improvements in my physical ability can be attributed to acclimation.  Furthermore, this demonstrates why individuals should undergo acclimatization (the physiological changes induced by the natural environment) prior to events in an abnormal environment.  

EDIT: One should note that for true acclimation and/or acclimatization occurs after 10-14 days of being exposed to the different environment.  As I have only been undergoing acclimation for 4 days, I have yet to be fully acclimated - however - cardiovascular changes can occur within 24-48hrs (such as increased blood plasma volume).

References:

Armstrong, L.E. & Maresh,C.M. (1991). The induction and decay of heat acclimatization in trained athletes. Sports Med. 12: 302-312.