Significant improvements in 5K and 10K times are possible by simply developing strength. In fact, during my 26 years coaching runners for the San Diego Track Club, I have determined that a strong running base is the key to an athlete's success. A strong base, combining all the right elements, will make you stronger and faster. Long runs, hill workouts, tempo runs and track intervals build strength and speed and this is a plan guaranteed to result in a 5K /10K PR.
Your weekly long runs have great potential to improve your performance, whether you run 5Ks or 10Ks. Once you have built your base to eight weeks with at least 30 miles per week, you can start doing long runs on a weekly basis. You should do a long run every week during the year. Other than easy recovery days, long runs are the only workouts you do on a regular basis throughout the year.
How long is the long run? Rather than focusing on mileage, you should run for time. One and one-half hours is ideal. During a run of that length, you'll recruit more muscle fibers, fire up your fat metabolism and even experience significantly higher heart rates than you would during a shorter effort.
Long runs also fatten up your weekly mileage, boost your maximum aerobic capacity (V02 max) and strengthen your leg muscles. The weekly long run will also increase your endurance—your ability to run for long periods of time without stopping. It's a good idea to use your heart rate monitor during your long run. For most runners, I have found that 139 to 150 beats per minute during a long run is ideal. If your heart rate goes higher than 150, you need to back off the pace. Remember you're not working on speed during the long run; you're building endurance.
Running hills will help you prepare for faster running you're going to do on the track. Hill workouts are designed to build muscular and cardiovascular strength. Choose hills that have a 4 to 10 percent grade and take approximately ninety seconds to run. Nearly 90 percent of all distance runners are deficient in muscular strength. When you run hills, you develop elastic muscle fibers—the most significant source of power. Because hill running requires both steady state and oxygen depleting efforts, it provides a good transition from aerobic to anaerobic capacity; intensity is important because it'll help you sustain a higher tolerance for the build-up of lactate acid in your muscles.
Like long runs, hills improve your endurance and give you the ability to maintain a hard effort when you race. It's important to concentrate on your form when running hills. If you're struggling to maintain your form, don't run as hard, and run only half the distance of the hill. When you approach the hill, you should shorten your stride somewhat, fully extend your legs, lift your knees and lean forward.
Lengthen your stride on the downhill. Like the long run, you'll run hills once a week, but you won't run them throughout the year. Once you've built your eight-week base, you'll run them for 12 to 15 weeks.
Tempo runs are the third key workouts for developing strength. They improve your stamina and help you develop both confidence and a sense of pace. An example of a tempo run is to warm up with an easy 10-minute jog, stretch, and then run for 20 to 25 minutes at tempo pace. Tempo pace is 10 to 15 per mile slower than your 10K pace.
The physiological secret behind tempo runs is to raise your lactate threshold velocity, the running speed above which fatigue sets in quickly. As your lactate threshold velocity increases, you'll run at faster speeds without getting tired. These runs are an excellent "bridge' to racing; they require you to run hard for relatively long periods. This is why you'll run them weekly for three months leading up to your competitive season.