Strength Training is an often neglected component of training for Triathlon. The common reasons sighted for this are; no time and/or don't want to get too big! You do have time, it is a total misconception that you need to do multiple hours in the gym to get benefits. You can definitely get significant strength gains with only one or two sessions per week. Depending on your other committments, I generally prescribe one session of 40minutes to 1hour. If you have the time or specific strength needs (rehabilitation or significant postural issues for example) then a maximum of two sessions of 30minutes through to 1hour per week.
As discussed below, Strength Training doesn't need to involve Hypertrophy (muscle gain) - significant strength gains can be achieved without gaining size/weight.
Following on from many years Personal Training which included Strength and Conditioning for many Rowing teams and via the NZ Academy of Sport for NZ Junior Representatives - Brendan Erskine has developed a model of specific Strength Training for Triathlon. The model is based on Functional Strength, delivers strength gains specific to Triathlon and fits into an overall Triathlon training programme.
Functional Strength training can improve your triathlon performance through improving your ability to produce muscular force, ultimately, making you a faster athlete.
The ‘functional’ element to it means that you are doing strength training that is designed to work on overall strength, core strength, balance, power, joint mobility, stability and movement through multiple planes. Performed correctly Functional Strength is also going to lessen your chances of getting injured.
The general progression of this type of training is to improve your overall strength and then muscular strength that is particular to swim, cycle and running movements. The major gains made are due to more efficient motor patterns (such as; improved firing frequency, synchronization of motor units, relaxation of antagonist muscles) of the force producing muscles with little or no muscular gain. Finally the strength gains are converted to improvements in power. The conversion from Muscular Strength to Power is important as it is important to retain the use of all your muscle fibre types - Power training is going to awaken those larger fibre types that are important to swim starts, accelerations, short sharp climbs and having a kick at the end of a race.
There is little need in the gym to specifically work on Strength Endurance. If you are doing 10-25 hours of Endurance Training per week then chances are you are doing hill climbing, resistance swim drills and wind training that are all going to work on strength endurance. Simply getting stronger is also going to have a positive effect on your muscular endurance.
One of the great aspects of improving your Functional Strength is the relative time investment, as little as 40 minutes per week can reap significant gains.