Q: I am a 41 year old bodybuilder/marathon runner. When NOT training for the marathon, my running consists of two types of run. One is Long Slow Distance of 8k or more. The other is a faster 4k with timing of 22 to 24 minutes, at almost constant speed throughout. Does this 4k run benefit my fitness in any way? Most speed training methods advocate interval training. Is there a place simply for a fast short run? Thank you for your answer.
The faster 4k run you mention sounds akin to an anaerobic threshold or tempo workout. These workouts are a staple of coaches training athletes for distances ranging from 800 meters to 10,000 meters. The initial goal is hold the intensity at about 85% of maximal oxygen consumption (think 85% of current two-mile time) for 20:00 to 25:00. It should come out to somewhere around 10k pace and should feel “comfortably hard.” Training at this tolerance will promote the efficient use of glycogen as the primary fuel, as well as yield cardio respiratory results. Short, quick running (200 meters or less) can be used to improve neuromuscular speed, conditioning the body to run more efficiently at faster speeds.