If you are looking to improve your swim speed for triathlon, you are looking to increase the amount of propulsion you can create and increase your ability to sustain that level. In essence you need to improve power and endurance of the muscles that produce front crawl movement. the obvious first port of call is to check your actual technique with a swim coach to check you are swimming as well as possible, this makes a huge difference in terms of your ability to create propulsion and your ability to waste as little energy as possible. It's always worthwhile seeking the help of a swim coach if this is the weakest aspect of your triathlon.

With regards to your gym training it's worthwhile checking your shoulder posture and flexibility as this can seriously affect shoulder mechanics. You need to check two things: have you got good all-round range of motion at the shoulder joint and can you perform various pulldown movements with correct mechanics? The shoulders should rise and wing as you reach up, but as you pull down you should be able to bring the shoulders down and stop them rotating forward. If you can't achieve these things look at doing some mobility and stabilisation work for the shoulders. If these are fine then you could do straight arm cable pulldowns to develop strength and medicine ball smashes to develop power. Both exercises are performed standing with no body movement; this helps develop core control helping you to stay straight and streamlined whilst in the water. The medicine ball exercise is the same movement as the pulldown, but you are trying to throw the ball into the floor as hard as possible whilst maintaining perfect form!

Progressions are:

*to create endurance - do more reps!
*do alternate arm - simulates swimming
*create a little rotation during exercises - mimics crawl even closer and is more challenging for the core.
*perform on unstable surfaces - one leg or bosu to increase core challenge

Remember:

*need to perform exercises that will balance all of this internal rotation work and maintain good posture/joint mechanics.

Good luck, and if this wasn't clear or there's anything you're unsure on let me know,

Gareth

I agree with the first poster on having someone check your technique, it can make a HUGE difference. Also, back exercises like pull-ups and rows are great for swimming