While we are not even to the fall season yet (though unbelievably close, where did summer go!) some athletes and their parents are already looking ahead to the winter sports season. They are looking for a an activity that will help them get in shape for basketball or hockey and they think running cross country sounds like a great idea. The popular belief is that by running for long distances you will build a base or reserve of conditioning that will serve the athlete well heading into the winter.
Before I go any further it is important to note that if long distance running is your main form of competition this does not apply to you at least not completely. There must be some type of specificity when training for any sport and for cross-country you have to be prepared mentally and physically to run for long distances. Though developing young endurance athletes would be well served to read on.
Let’s first consider the type of running that is involved in cross country it demands a steady pace throughout the race with the exception of the final kick where a runner may exceed that steady state to separate from a competitor or to run a personal best time. The pace of running in cross country is not at or beyond your limit if it were your body would shut down from depletion of energy supply due to a lack of oxygen. The strategy is to build tolerance to run as fast as you can over a given distance at just under your limit. In other words you are training your body to run not to fast but not to slow.
In team sports such as basketball and hockey that type of training will get you beat! These sports demand quick and short bursts of explosive speed that last mere seconds followed by a slow jog, walk, or complete stop to recover for another short burst of speed. The running in most team sports covers very shorts distances with multiple starts and stop with change of directions. These short runs are at or beyond your maximal limit and they occur frequently. Running at steady rate of speed below your limit in straight line will not provide the conditioning you need.
Watch any football, soccer or basketball game and rarely will an athlete run for more than 20 yards in a straight line and the duration will be somewhere around 4 seconds or less. You will never hear a broadcaster or a coach say that the athlete was so fast that they missed a play. On the other hand you will often see and hear about an athlete that came up just short because they couldn’t get their fast enough.
Soccer players typically run five to eight miles in the course of a match and alter their direction or speed every 6 seconds. A study of an English Premiership striker broke down that distance by type of activity. In the course of running more than 10 miles, the player walked 4 1/2 miles, jogged 3 1/2 miles, strode one mile, moved backward or sideways one mile and sprinted about a 1/2 mile. In all these athletes spend around 60% of their time walking or standing and though they may have jogged (steady state like cross country) 3 ½ miles it was not consecutively. 
In the NFL the average plays lasts only 4 seconds and the ratio of action to inaction is approximately 10 to 1. The average game has 11 minutes of action with players’ standing/milling around for 67 minutes.  Running in a straight line for 3-4 miles isn’t going to prepare you for the demands of this sport either.
There are three types of skeletal muscle fibers (slow, intermediate, and fast) and although some muscles have predominance of one fiber type, most contain a mixture of fiber types, which are most suitable to a particular activity.
The slow muscle fibers are fatigue resistant and are best utilized during endurance activities such as running a marathon or maintaining our posture all day long. Fast muscle fibers fatigue quickly but are capable of producing great force and speed such as jumping to dunk a basketball ball or throwing a fastball. And the intermediate muscles fibers serve that middle ground for activities that require a blend of speed and endurance such as running a 200-meter dash.
Everyone’s muscles contain a mixture of the three fiber types, though some people have relatively more of one variety. These differences are genetically initiated but can also be modified through an athletes’ training. For example marathon runners have a high percentage of slow muscle fibers (about 80%), while those of sprinters contain a high percentage of (about 60%) of fast fibers. *
I am sure you have heard this phrase before; what came first the chicken or the egg? Maybe the athletes with a greater reliance on slow muscle fibers preferentially choose endurance events because they excelled at it and quite possibly the athletes with a predominance of fast fibers choose short burst activities like team sports and sprints because their fibers are most suited for them.
But that middle ground those intermediate fibers can be influenced through training particularly in pre-pubescence. It should also be noted that these “swayable” fibers will revert to the prior status once the exercise stimulus has been removed, so quite literally use them for speed or lose them to mediocrity.
Speed is a commodity that allows for success in all sports and it must be prioritized before any other form of conditioning. Once you have the speed than you can work to build the endurance but the reverse is unlikely to happen this is particularly so in regard to developing young athletes.
It should also be noted that children’s response to exercise is mainly non-specific. Children will improve their endurance for example, just by virtue of doing any type of exercise whether that is short burst activity or steady state exercise like running a mile. So if you want a child to improve their endurance you don’t necessarily have to have them run at a steady state for a prolonged period of time. They will get just as much benefit and even more through short burst activities like tag. Steady state is boring for many kids and it doesn’t require the multi-directional speed and agility development that must be developed in the skill hungry years. Endurance, like strength is a fitness marker and can be developed and improved upon throughout most of the life span. Speed must be developed early; you can’t catch up to it later.
Endurance is an important quality for any athlete but it’s how you develop that endurance and when that is key. Young children should play games like tag and capture the flag, lots of all out bursts of speed. For the more mature kids that want more of a structured-conditioning program they should focus on running sprints that cover short to moderate distances (10-60 yards). They should do so repeatedly with short rest periods and they should go as long as they can maintain the quality of the work. For example one of my favorite conditioning drills for athletes is to have them sprint for as long and hard as they can for a defined period of time, say 7 seconds. After that time elapses we mark the point they reached. They will walk back to the starting line usually a 1:30-2:00 minute rest and then repeat (maximum of 10). The workout ends when they can no longer make it to their marker within that same defined time. Some kids may have a short conditioning workouts but there are ways to make up for that (that’s another article in itself).
All that said, we should never discourage a child from taking part in any type of physical activity in the rare case that a child does enjoy running for long distances. However, just like we monitor their dietary intake (just because they like apples with peanut butter they shouldn’t have that for every meal) we have to ensure they experience a broad variety of activities to develop a balanced movement foundation.
 Marieb, Elaine Nicpon. Essentials of Human Anatomy & Physiology. San Francisco: Pearson/Benjamin Cummings, 2006. Print.