As a follow-up to my last post, here are some cross training exercises that build core strength, which is very important for runners. The core muscles improve running economy, speed and power to help you run faster with less effort.
These are also from RunningPlanet.com as written by Rick Morris:

ABDOMINAL CRUNCH

This is a body weight exercise or can be performed using single station or multi-station machines.

TECHNIQUE

* Lie face up on a mat. Flex your knees and bring your heels close to your buttocks. Cross you hands over your chest. Tuck you chin into your chest.
* Slowly curl your upper body towards your knees until your shoulder blades leave the floor. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the floor.

CORE STABILIZATION

This is a body weight exercise.

TECHNIQUE

* Lie face down on a mat. Support your weight with your feet and forearms. Tuck your pelvis so that your hips are pressed forward and your body is straight. Hold this position.
* Holding the above position, lift your left arm. Hold that position for 20 seconds. Return the left arm to the support position and lift your right arm and hold for 20 seconds. Return the right arm to the support position and lift your left foot off of the mat and hold for 20 seconds. Return the left foot to the mat and lift the right foot and hold for 20 seconds.
* Now comes the fun part. Return the right foot to the mat. Now lift your right arm and left foot at the same time. You should now be supporting your body with your left forearm and your right foot. Hold that position for 20 seconds. Now return the right arm and left foot to the mat and lift your left arm and right foot and hold for 20 seconds.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Use a controlled curling motion throughout the exercise.
* Be sure to keep your hips tightly tucked during this exercise. Do not allow your lower back to arch or curl. Keep your body very straight.

DOUBLE CRUNCH or V-CRUNCH

TECHNIQUE

* Lie face up on a mat. Hold your feet off of the floor with your lower leg parallel to the floor and your upper leg perpendicular to the floor.
* Slowly curl your upper body towards your knees until your shoulder blades are off the floor. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. At the same time, using your lower abdominal muscles, push your hips up off of the floor. This motion should be like pushing your knees straight up toward the ceiling. It should not be a rocking motion.
* Slowly allow your upper body and hips to curl back to the floor.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

EXERCISE BALL ABDOMINAL CRUNCH

This is a body weight exercise that is performed using an exercise ball.

TECHNIQUE

* Lie on the exercise ball so that the ball is supporting your lower back. Place your feet wide and flat on the floor for balance. Cross your hands over your chest or use them to support your head. Do not pull on your head. Tuck you chin into your chest.
* Slowly curl your upper body upward. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the starting position.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

EXTENDED ARM CRUNCH

This is a body weight exercise.

TECHNIQUE

* Lie face up on a mat. Flex your knees and bring your heels close to your buttocks. Extend your arms over your head and clasp your hands together. Tuck your chin into your chest.
* Slowly curl your upper body towards your knees until your shoulder blades leave the floor. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the floor.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

OBLIQUE ABDOMINAL CRUNCH

This is a body weight exercise or can be performed using single station or multi-station machines.

TECHNIQUE

* Lie face up on a mat. Flex your knees and bring your heels close to your buttocks. Cross you hands over your chest. Tuck you chin into your chest.
* Slowly curl your upper body towards your knees and rotate your body so that your left elbow moves toward your right knee. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the floor.
* Alternate between moving your left elbow to your right knee and your right elbow to your left knee.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

RAISED LEG CRUNCH

This is a body weight exercise.

TECHNIQUE

* Lie face up on a mat. Hold your feet off of the floor with your lower leg parallel to the floor and your upper leg perpendicular to the floor.
* Slowly curl your upper body towards your knees until your shoulder blades are off the floor. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the floor.
* THINGS TO WATCH OUT FOR
* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

RESISTED ABDOMINAL CRUNCH

This is a body weight exercise or can be performed using single station or multi-station machines.

TECHNIQUE

* Sit with your back flat against the bench. Stabilize the resistance against the front of your shoulders.
* Slowly curl your upper body towards your knees until your shoulder blades are curled away from the bench. This should be a rolling, curling motion. Concentrate on strongly contracting your abdominal muscles. Hold this position for a moment.
* Slowly allow your upper body to curl back to the bench.

THINGS TO WATCH OUT FOR

* Breath throughout the exercise.
* Exhale on the upward portions and inhale on the downward portion.
* Use a controlled curling motion throughout the exercise.

Cross training can significantly improve your running performance and help to prevent injury. Here’s what running expert, Rick Morris, says about it on runningplanet.com:

Distance runners all over the world are beginning to add cross training workouts into their weekly training routine. Does cross training help you as a distance runner? The law of specificity insists that the most appropriate workouts for any athlete are those that match their goal. In the case of distance runners that means the most valuable workouts are distance running specific workouts. That may suggest that cross training workouts are of no value to distance runners. While running workouts are by far the most important ones for improving your distance running performance, some cross training workouts do provide you with valuable benefits that will improve your performance as a distance runner.
How can cross training improve your distance running performance? Cross training won’t directly improve your endurance, stamina or speed but there are several indirect ways it will make you a better distance runner.
Improved Strength and Power
In my opinion the most valuable type of cross training is strength training. A properly designed strength training program will improve your running strength, power, muscle elasticity and running economy. There have been many recent studies showing that strength training will improve your performance in all race distances from the mile to the marathon.
More Quality Workouts
Most of your gains in VO2 max, vVO2 max, lactate threshold and speed are gained through high intensity running. Unfortunately you can’t run hard every day. You need easy running days or recovery days to allow time for your body, mind and muscles to recovery and strengthen. That’s were some high intensity cross training comes into play. While your overtaxed running muscles may not be able to tolerate consecutive hard runs you may be able to hop on your bike for a hard training ride between hard running sessions. The high intensity cycling workout will help improve your fitness while using fresher muscles that weren’t abused during your hard training run.
Active Recovery
Cross training shouldn’t always be high intensity. There are times when you need total body recovery. After a 22 mile long run or a brutal interval session your body may need a couple of days of recovery. Do you need total rest? Maybe not. Instead of total rest you could hop on your bike for an easy endurance ride, jump in the pool for a relaxing swim or schedule a game of tennis with your running buddy. The active recovery will burn some calories and also assist with muscle recovery.
Active Rehabilitation
No one wants to suffer from a running injury but they are almost inevitable. When you’re injured you need to back off on your running until your injury is rehabilitated. During that time off your fitness and endurance can suffer while your body fat levels creep up. A good way to avoid weight gains and decreases in fitness during injury rehabilitation is to do some cross training. Pick a cross training activity that doesn’t place stress on your injured muscles or body parts. Cycling, swimming and deep water running are usually good choices.
Decreased Body Fat
There is no question that excessive body fat weight can have an adverse affect on your running performance. If you don’t believe it go out for a 6 mile run wearing a 10 pound running vest! The problem with losing weight as a distance runner is you must do it while maintaining appropriate nutritional levels. That means dieting is out of the question. So, you need to burn additional calories. Cross training gives you an efficient way to burn extra calories while still getting enough recovery between hard running workouts.
Improved Muscle Balance
Distance runners tend to have highly developed hamstring and calf muscles with under developed quadriceps muscles. Muscle imbalances can cause problems with your posture and running mechanics. Cycling is an excellent way to build up the strength of your quadriceps muscles and avoid muscle imbalance. Strength training is also a great way to keep your muscles in balance.
Injury Resistance
There are two advantages to strong muscles in terms of injury resistance. First, strong muscle fibers are more resistant to strains. Second, stronger more powerful muscles provide more support to your joints. Strength training is one of the best ways to improve the strength of your muscles and help be a more injury resistant runner. Not only will strength training build your muscle strength but it will also improve the strength and injury resistance of your bones and connective tissues.

Personal Running Trainer is developing an ‘app’ for the iPhone / iPod Touch which will allow users to listen to the coaching instructions but choose their own background music. Look for it in the Apple app store this summer!