Weight Training.

If done properly, weight training can improve strength and power, and efficiency. I believe that most will benefit from weight training, but it does need to be specific to an individuals need. Some athletes can be prone to "bulking up", and need to be careful about how they do their weight training. Weight training should be an "add-on" rather than an "instead of" training session. If you are very time limited, specific training (swimming, cycling, running etc) will usually be more beneficial.

Weight training needs to be specific - to the exercise you are trying to improve, and to optimize your personal strengths and weaknesses. Your program also needs to be specific for each phase of your build-up. You and your coach should determine your specific weight training program, of what exercises, and how many sets and rep's you do. 

Below is a table showing a number of common exercises that are more specific to triathlon, cycling, swimming and or running. Core exercises are not included here, but it is recommended that these are also included as an essential part of any program. 

Weight training exercises.

Upper Body
1. Bench Press	Lying on your back. Grip the bar so that when you lower it to your chest your arms are at 90 degrees. Lower the weight in a controlled manner - then press it back up. Keep your lower back firmly against the bench - it maybe better to have your feet on the bench to avoid "cheating" by arching your back.  Variations: wide/narrow grip, incline/decline bench.
2. Military Press	Grip similar to the bench press. Lower weight behind neck (don't drop weight onto your neck!) and press weight back up. This is better done on a machine where you do not have to move weight behind your head.
3. Tricep extensions	Lock  elbows into kidney area and lean forward. Push weight down, and control back up until forearms are horizontal. Your elbow should not move.
4. Lat Pull downs	A wide grip on the bar, and pull the bar down to the top of your chest. Your upper body should be leaning slightly backward, but there should be no movement in your upper body while performing the exercise. If you can pull the bar below chest level - then the weight is too light.
5. Seated Rows	Seated in the machine, body up-right, legs slightly bent in front. Pull the weight back and squeeze the upper back in the final part of the motion. Return the weight in a controlled manner. The upper body should remain stable throughout the exercise (do not rock torso back during contraction).
6. Bent fly's	Standing with dumbbells, leaning slightly forward. Raise dumbbells in a controlled manner with a slight bend in the arms throughout. focus on the muscles in the upper back contracting.
7. Pull over's	Lying on a bench with a dumbbell held in both hands. Raise dumbbell directly upward to the start position. With arms straight, lower dumbbell above your head as far as you can (without back coming off the bench).
8. Upright row	Hold Barbell with a narrow grip (thumbs together), in the center of the bar. Raise bar until it is below your chin, keeping it close to your torso throughout.
9. Biceps curl	Use barbell, or dumbbells, holding with palms face up. Lock elbows into kidneys and raise bar(bell), curling wrist at the top. Elbows do not move!
10. Dips (Assisted)	On parallel bars, lower your body until there is at least a 90 degree bend at the elbows. Raise yourself back up (until arms are straight). You can use an assisted dip machine or use an assistant is your own body weight is too much!
Lower body
Step-ups	Step up onto a platform that gives approximately a 90 degree bend at the knee when you place your foot on the platform. Step down from the platform in a controlled manner with the same leg you stepped up with (don't just drop down). Repeat with other leg.
Leg Press	Sit in leg press machine with feet shoulder width apart. Feet should be reasonably high on plate (to work the glut's more). Press legs out straight - but do not lock them out (pushing through the heels). Lower weight back down as far as you can (should be a 90 degree bend at the knee - or the weight is too heavy).
Squats	Start with weight on shoulders (either machine or barbell). Lower down as far as you can, looking up (to keep your back straight), and sticking your butt back. There should be at a 90 degree bend at your knee when you have lowered down. Press the weight back up (push through heels). Go down slow and up fast but controlled.
Lunges	Take a large step forward, and lower the rear knee so that it just touched the ground. There should be a 90 degree bend in the front knee. Keeping the feet in the same position rise up, then down (without front knee moving forward). Down slow and up a little faster but in control.
Calf raises	Stand with forefoot on a platform, with heels as low as they can go. Keeping legs straight, rise upward so that you are on tip-toes and hold. Lower back down slowly. Use a machine, or do one leg at a time.
Leg extension	In the leg extension machine, start with legs bent, and extend legs straight. Hold at extension, and lower slowly.
Leg curl	Start with legs straight and curl at the knee against the machine (either standing or lying down). There should be no movement from the knee upward (do not swing the torso, or arch your back).