During the summer of 2009, we had only four days above 90, and two of those were on consecutive days in early September. During the month of July in 2009, we never even met the average daily high for any day. The summer of 2010 has actually been closer to an average summer for our area in terms of days above 90 and with just slightly above normal temperatures overall. While the average daily high has only been about 1.5 degrees above normal, the average daily low has been about 3 degrees above normal. The humidity has been the real problem and the reason for our high afternoon heat indexes.
Training and racing in this weather can be draining. I've been working with Dawn Weatherwax at Sports Nutrition to Go since February and one of our goals was to minimize the loss of performance on the really hot days. Losing 2% of your bodyweight can cause a 10-20% reduction in performance. Dawn had me chart my weight before and after training or racing, the time spent on the bike, and the amount and type of fluids consumed. The goal was to come back from all rides within 1% of my starting weight, or with less than 1.7 lbs lost.
I do a lot of my training at lunch so I've had plenty of opportunities to ride in the heat of the day. Even while going through 3-4 20 oz bottles in 90 minutes I was still ending some rides with a 4-6lb weight loss, or about 2.3 to 3.5%. The power data from the rides backed up the power loss that would be expected as fluid was lost and not adequately replaced. If I was doing 3-5 intervals of 10-12 minutes, my best power was always the first two. Several times my last effort was my best but I think this was the typical 'its the last one, go for it' boost.
Part of the testing that Dawn did with me was measuring sodium loss. She determined that I lose about 1000 mg of sodium every hour when training. When you combine that with the fluid loss, we're really talking about having to consume a lot of fluids and a lot of sodium on long and/or intense rides. I've been riding a century plus almost every Saturday since April and I've finally gotten to the point that I can come home at my starting weight and having replaced the lost sodium. I'll go through about 200 oz of the Gatorade Pro Series 02,and add a Gatorlyte (770 mg sodium per pack) or two along the way. This is all dependent on the weather conditions but it just shows you how much you have to take in to maintain the fluids.
At the Cleves time trial this past week, the weather was challenging to say the least at 5:30 when I went off with the early riders. My truck showed the temperature at 100. I only warmed up for about 20 minutes (10 at a pretty light pace and then ten minutes with just a few one minute time trial pace efforts). I drank while warming up and while waiting to ride the event. I took in 40 oz during this time. All was going well for the first half of the course which has more shade than the second half. I was averaging 27.8 at 5.1 miles, usually the slower half of the course but this was one of my fastest rides this year, at least so far. Right where we exit the woods and come out by the power plant, everything changed, and quickly. The sun was right over us and the heat from the road was noticeable. The final miles to the finish were as difficult as I've ever experienced at Cleves. I never take a drink riding that event but I pulled the bottle out a couple of times on some of the uphill sections where losing some areodynamics wouldn't hurt my speed as much. I ended up finishing with my third fastest time of the year but it wasn't much fun. I also lost speed on the second half, which is usually where I gain speed. While helping with the timing at 7:00 and until I got home around 9:00 I drank about 120 oz of the Gatorade Pro 02, and I was still down 3 lbs.
At Masters Nationals I saw riders warming up for the time trial on their trainers under tents in the parking lot. Talk about hot, and counter productive. It is possible to be too warmed up, and I think that was a problem for some riders on that day. If the loss of fluids is going to cause a performance drop, I'd rather start off completely topped off than already at a deficit.
Be sure to track your weight before and after rides and replace those fluids with proper pre, during, and post ride hydration. Also, if you're really interested in tracking your diet and sleep patterns, go to www.bodymedia.com. I've been wearing the armband for several months and the data is amazing.