Tuesday, December 11, 2007
What is lactate threshold? What sort of lactate threshold workout do you recommend for a beginning runner?
Lactate Threshold (LT) is a term that describes a level of exercise intensity at which lactic acid accumulates in the bloodstream faster than it can be removed, or metabolized. Training just below this "threshold" allows the body to adapt and adjust to anaerobic effort. While aerobic activity generally involves lower intensity heart rate efforts performed over a prolonged period of time, an anaerobic effort involves the ability to perform increasing heart rate workloads with less oxygen - while running faster. Lactate threshold training teaches the body to tolerate moderate levels of lactic acid in the blood, through training at a pace that is significantly faster than aerobic conditioning - where very little lactic acid is produced, and much more oxygen is available.(Blame those heavy legs, and your inability to maintain the "stress" of faster paced running on several physiological factors - one of which includes exceeding your LT). The ability to tolerate these negative byproducts in the bloodstream can often be the deciding factor between running faster towards the finish line - or simply surviving a race.
An individual's lactate threshold can improve with training, and runners with higher lactate threshold levels are capable of working for longer periods of time at higher levels of energy expenditure - allowing them to run faster than athletes of equal aerobic strength - but who possess a lower LT.
The optimal method of finding your lactate threshold is best done by an exercise physiologist drawing and analyzing blood, during a maximal test on the treadmill. Most athletes' LT training pace is approximately 25-35 seconds per mile slower than their 5K pace, and generally corresponds to 80-90% of Maximal Heart Rate (*MHR).
One of the best ways to train your lactate threshold is to institute tempo running into your training regimen once or twice weekly. The term "tempo run" was popularized many years ago by legendary coach, exercise physiologist, and Olympian, Dr. Jack Daniels. It describes a workout that is conducted at a pace "held" just below threshold. Tempo runs can be an extremely important aspect of your training regimen, when performed properly, and at the right time in your training.
I would advise a beginning runner start with a 35-40 minute tempo run that would include a 10 minute warm-up at 60-75%MHR - followed by 15-20 minutes of tempo running at 80-85%MHR - and which concludes with a 10 minute cool-down jog at 60-65%MHR. Experienced distance runners should consider a 55- 60 minute tempo run which would include a 15 minute warm-up - 20-25 minute Tempo Run at 85-90%MHR - and a 20 minute cool-down. Running within heart rate zones is critical to lactate threshold training - as you are hoping to elicit a specific physiological response. Make it a point to determine your heart rate zones using the Karvonnen formula which factors in both your age, and resting heart rate. Use a heart rate monitor during your tempo run, to help eliminate any extra "guesswork". While an LT workout will feel challenging - or comfortably hard - it should not feel like race effort. Remember, you are working at the borderline of threshold, not running over the edge of the abyss.