I hear what you\'re saying, Rich. Here\'s what you are referring to, I think:
Yes, there is very old research that shows lasix slightly - slightly - slows horses, estimated to be due to the side effects of dehydration.
About 6-7 years ago, there was a study with 8 Thoroughbreds that showed horses improved their performance slightly, by increasing the duration of time (not speed) they could run. They could run slightly longer, but not faster.
The study showed in increase in VO2max (oxygenation volume). The study attributed the increased performance to the 20-30 pound water weight loss from dehydration, rather than improvement in decreasing EIPH. You can read that abstract here:
http://www.ncbi.nlm.nih.gov/pubmed/17402434There was another older study in the late 1990\'s that analyzed the actual racetrack performance at 6 furlong races of all TB\'s in the US and Canada for a period of time on dirt tracks. 74% of horses ran on lasix.
The horses on lasix performed better, won more money, finished in the placings more frequently.
Here\'s a quote from the study that is directly to your concern: \"... horses receiving furosemide had an estimated 6-furlong race time that ranged from 0.56 +/- 0.04 seconds (least-squares mean +/- SE) to 1.09 +/- 0.07 seconds less than that for horses not receiving furosemide, a difference equivalent to 3 to 5.5 lengths.\"
Again, the study could not conclude \"why\", but the improved results were measurable.
My opinion, and this is based also upon my personal experience and participation with multiple lasix research studies published in the 1990\'s that first established the actual measured cardiac and pulmonary pressure differences in TB\'s on and off lasix at speed: Is lasix a \"hop\" that artificially increases speed and performance? No. Does it enable peak performance? Yes.
I know that may seem like parsing a semantic difference, but my view of lasix is that, if we are going to run horses professionally at the fast speeds on dirt, we have to protect their lungs from the associated damage if we can.
Let me know if you\'d like to read the studies mentioned, I can forward to you.