After a succession of ever-slower 5K times this summer, I dug around for an excuse. My digging turned up something better — a genuine reason.

The optimum temperature for running performance, at least statistically, is 51 degrees. That's the temperature that produces the fastest marathon times, but it's one we haven't seen for quite a while.

As the thermometer climbs above 60 degrees, heat begins to influence distance running performance. Temperatures above 90 degrees affect not only performance, but a runner's health and safety.

There's no way to predict exactly how heat will affect the finishing time of your next steamy 5K, but separate studies by sports performance experts Jack Daniels and Alan Glover suggest guidelines.

Daniels found that elite athletes' performances declined by up to 5 percent as the thermometer climbed from 60 to 90. Glover's statistics suggest decreased performance of 10 percent or more for average athletes.

With Daniels' guidelines in mind, an elite athlete's 5K time might slow from 15 minutes to a still speedy 15:45. Using Glover's estimates for average weekend warriors, a 22-minute 5K finish in cool weather could translate to a 24:12 or slower in hot temperatures, a hefty difference

Of course, nothing is quite that simple. Heat and humidity affect individuals differently. Trained athletes can handle the heat better than sedentary folks. And runners who have had a previous heat injury are more likely to experience another one.

Heat stress is just one of any number of life stresses that conspire to slow race times. Runners who suffer from allergy- or exercise-induced asthma also feel the effects of hot weather more than nonasthmatics.

Runners who come to the starting line overtrained, overtired or dehydrated suffer more physically and psychologically in hot races. And those runners with unrealistic performance goals who overextend their limits face not only discomfort, but a complete meltdown in the form of heat exhaustion or heat stroke.

It's sometimes hard to predict the effects of heat in terms of minutes and seconds. The wisest thing runners can do is to prepare for hot weather races by gradually getting used to the heat, plan for a conservative pace and prevent heat injury by setting reasonable goals and being aware of heat injury symptoms on the run.

It takes at least two weeks to get acclimated to hot weather running. In that period, runners may have to back down on training intensity and duration to prevent extreme fatigue or heat injury.

Be aware of the heat stress index number or American College of Sports Medicine flag color at race start time and adjust goals accordingly.

The HSI crunches the numbers of several weather measurements to produce an indicator of how much the heat will affect performance or safety. ACSM colors range from green for safe to black for dangerous running conditions.

Don't forget to check the numbers before heading out to that next 5K or download a heat stress adviser or event safety calculator for PDA or computer from www.zuni.org.

Saturday, 8 a.m.: Hot Harry's Runners Group Run, North Park. Starts at Stone Field for easy run.Saturday, 8:30 a.m.: Raider Maze 5K Run-Walk and 1-Mile Fun Run, Harmony. Run on Seneca Valley High School campus. 724-538-8940 or raidermaze@yahoo.comSaturday, 8 a.m.: Run with the Deer Flies 25K, Yellow Creek State Park. Cross country adventure. 724-349-7085 or jswauger@comcast.netSaturday, 9 a.m.: Freeport International Baseball 5K, Freeport. 724-295-4492 or www.fortheloveofthegame.orgSaturday, 9 a.m.: Turtle Trot 5K, Turtle Creek. 412-823-8595Saturday, 9 a.m.: Leukemia and Lymphoma Society Team in Training Meeting, Cranberry Township. 800-482-8326 or www.teamintraining.orgSaturday, 10 a.m.: Butler County Family YMCA Youth Triathlon, Zelienople. Swim, bike, run event for ages 6 through 12 in Zelienople Community Park. 724-452-9122 or jgroves@rsymca.orgWednesday, 6 p.m.: Up-N-Running Group Run, Valencia. Change of day and time for summer. 724-898-2525 or www.runpa.comJuly 29, 6 p.m.: Team in Training Meeting, Fox Chapel. 800-482-8326 or www.teamintraining.orgAug. 2, 9 a.m.: St. Barnabas 5K, Valencia. 724-444-5512 or www.stbarnabas5k.comAug. 2, 9 a.m.: Bob Swanson Memorial 5K, Mount Jewett. 814-778-5940 or kirbyp@verizon.netAug. 2, 7 p.m.: Debbie Green Memorial 5K Run-Walk for Leukemia, Wheeling, W.Va. 740-859-0704Aug 9, 8:30 a.m.: Roebling's 5K Run-Walk, Saxonburg. Second race in Saxonburg Distance Series. 724-586-6118 or tmelis@zoominternet.netAug. 9, 9 a.m.: Brookline Breeze 5K, Pittsburgh. USATF Three Rivers Open and Masters Championship. www.brooklinebreeze.comAug. 9, 9 a.m.: Rimersburg Cookie Daze 5K, Rimersburg. 814-473-6427.Aug. 13, 7 p.m.: Courtney's Ice Cream Race 5K, Grove City. Run then eat. Final race of Twilight QUAD series. 724-866-1374 or smc@runhigh.comAug. 16, 8 a.m.: Parkersburg News and Sentinel Half Marathon, Parkersburg, W.Va. Cash prizes, no day-of-event registration; www.NewsandSentinelHalfMarathon.comAug. 16, 9 a.m.: Armstrong County YMCA Summer Fun 5K Run-Walk, Kittanning. 724-545-9622 or kknepshield@armstrongymca.org.Aug. 23, 8:30 a.m.: Tom Murray-Cranberry Township Aquathlon, Cranberry Township. Run three miles, swim 400 meters, run two miles in North Boundary Park. 724-774-5746 or jkercovich@yahoo.com

<B>Ellwood City Ledger 10K, July 5:</B> Jake Walker, 1st Overall M, 30:27; Patricia Vargas, 1st Overall W, 37:45; Bethany Walker, 2nd Overall W, 41:00; Leslie Kramer, 3rd Overall W, 42:29; Dustin Smith, 1st 14-19 M, 37:27; Jonny Cortez, 3rd 14-19 M, 39:23; Chris Ludwig, 1st 20-26 M, 40:59; Mike Covert, 1st 41-45 M, 41:15; Jeff Wiley, 3rd 46-50 M, 41:24; Frank D'Ambrosio, 2nd 41-45 M, 42:52; Frank Sassaman, 1st 51-55 M, 42:55; Curt Grimm, 1st 56-60 M, 43:33; Corrie Piccirillo, 3rd 20-26 W, 46:22; Cindy Grimm, 1st 51-60 W, 47:21; John Antinossi, 2nd 61-80 M, 47:36; Tim Powell, 2nd 56-60 M, 47:49; Carrie Smith, 3rd 27-33 W, 52:18; Kristen Kelosky, 1st 41-45 W, 52:19; Joe Vitullo, 3rd 20-26 M, 53:57Michael Poff, 3rd 61-80 M, 54:06; Alex Kosovic, 1st 13 and under M, 57:11; Angelo Williams, 2nd 13 and under M, 59:00; Lou Lodovico, 1st 80 and over M, 59:15; Isabella Williams, 1st 13 and under W, 1:00:15; Emily Medlin, 2nd 13 and under W, 1:01:00; Margaret Kempel, 2nd 61 and over W, 1:20:50;Phil O'Hara, 43:47; Tim Weil, 43:51; Dean Rippe, 44:46; Russ Ochsenshirt, 44:57; Jeremiah Friday, 45:00; Brian Connell, 45:13; Kevin McCaslin, 46:36; Scott Brown, 47:12; Michael Farah, 48:44; David DeCaria, 48:51; Bruce Hall, 48:54; Sara Ialongo Huber, 49:40; David Crowe, 50:09; Ron Hartle, 50:52; Dino Scialdone, 51:07; Phil Barner, 51:09; John Linville, 51:18; Frank D. Martz, 51:49; Joseph Mancini, 53:17; Len Yensull, 54:02; Rob Taylor, 54:23; Maggie Ewing, 54:32Mark Linville, 54:38; Jeff Syphrit, 54:44; Kaylee Kaszer, 54:51; David Barensfeld, 54:56; Tod Custer, 55:49; Tonya Barnoff, 57:03; Chris Price, 57:13; Jeff Krosovic, 57:17; Cassie Leymarie, 57:32; Ed Leymarie, 57:33; Gale Mussey, 57:40; Tom Murray, 58:11; Stacie Doughty, 59:42; Monica Lynn Susanin, 1:00:48; Chuck Susanin, 1:01:22; Megan O'Hara, 1:02:41; Sherree May, 1:12:34; Lauren Genova, 1:18:38; Lauralee Zalesnak, 1:21:56; Al Crowther, 1:27:09<B>Corry 5K, July 6:</B> Steven Battaglia, 1st Overall M, 16:51; Herb Cratty, 2nd Overall M, 17:38; Kimberly Turner, 1st Overall W, 19:34; Jeff Lynn, 1st Masters M, 18:08; Jamie Tomcho, 3rd 12-15 M, 21:56; Kim Keely, 1st 25-29 W, 23:09; Roxanna Altman, 3rd 50-54 W, 42:56; Hazel King, 1st 65-69 W, 54:30Send comments and suggestions: 435 Cherry Valley Rd., Saxonburg, Pa. 16056. Phone: 724-352-4395. E-mail bigp16@connecttime.netPat Neubert is the running columnist for the Butler Eagle.