Weight training generally strengthens all muscle groups so it is advised to include a resistance training program as part of your complete preperation. For the novice athlete trying to run a first marathon or triathlon, doing some resistance training can also decrease the likelihood of injury. Resistance training, when performed, should be in addition to the required training time and shouldn't go over 20% of overall program. Gym membership and weight training equipment could be used but it is not quite necessary, the idea is to make them as simple and accessible as possible so that you will be more likely to do them.
In endurance sport, high levels of strength are not desirable although a certain amount is necessary. In fact most elite distance athletes are thin and under-muscled. The reason is that just to carry more weight in any form requires more ATP that could increase the speed of running if there were not excess weight. Elite athletes do not want to bulk up with unnecessary muscle mass. They need certain amount of muscle mass, particularly in the legs, but heavily muscled legs and upper body, if anything, will be a disadvantage. Many elite distance athletes will do some resistance training, classified as muscular endurance training as opposed to strength training. Muscular endurance training differs from strength training with respect to the amount of resistance used and the number of repetitions performed.
The muscle groups that are most important to the runner are the calf (gastrocnemius and soleus), hips (gluteus maximus), thigh (quadriceps and hamstrings), abdominal, lower back, shoulders (pectoralis major, deltoids, latissimus dorsi), and the arms (biceps and triceps). Special mention should be made regarding to core muscles, the abdomen and the lower back. Many athletes suffer from some type of low back problem as running and cycling are hard on the back, particularly if the supporting structures are not well developed. The muscles of the abdomen and the low back are critical to maintaining proper structural alignment in the back so that back problems are less likely to occur.
The Warm-Up and Cool-Down
The warm-up for lifting weights is very similar to the warm-up for running. You should use lightweights to warm-up with, do 10-15 repetitions. This will allow your muscles to warm up and loosen. The cool-down is similar to the warm-up in reverse, with some stretching and relaxation exercises.
The general rule about weight lifting is heavy weights with few reps build strength and bulk and light weights with many reps increase muscular endurance. 10-15 repetitions multiple 3 times should be performed where the last set should consist the greatest amount of weight. Rest 30 seconds at the completion of the first set, and do some stretches to keep your muscles and joints loose.
You should always start working with a very light weight. Increase the weight gradually and as you are able to do more than 10-15 repetitions in your last set with the designated resistance, increase the resistance and work your way back up in your next weight training.
Weight exercise examples
The Bench Press - Lying flat on your back, face up, press the weight straight up from you. This strengthens your arms, chest, and upper torso.
Sit-ups with Weights - Lying on the floor, with knees bent and feet hooked under an immovable object put your hands behind your head and bring your upper body bent at the waist, to your knees. This exercise strengthens your abs and core muscles.
Step-ups - Stand holding the weight with both hands behind your neck, put one foot on a sturdy box and step up with the other. This strengthens the Achilles tendons, calves, and quadriceps.
Toe Raises - Stand holding a weight behind your neck, raise yourself up onto your toes. This exercise strengthens your calf muscles, Achilles tendons, and ankle joints.
Reverse Curls - Stand holding the bar on your quadriceps. Keep your back straight, not allowing your body to swing, and bring the bar up to your chest. This exercise develops the forearm.
Push Ups - Lie chest-down with your hands at shoulder level, palms on the floor and slightly more than shoulder-width apart. Straighten your arms as you push your body up off the floor. Do push-ups to strengthen arm and chest muscles.