Of the three triathlon disciplines, running causes the majority of injuries so the type of surface that you run on, as well as the frequency and duration of your training, deserve very careful consideration. As such, low-impact training options are the ideal way to supplement standard running sessions.
Though there are various versions available, the cross trainer (CT) has, in basic terms, two independent paddles that you step on while holding a static bar or moving independent arm levers. Research has shown that exercising on a cross trainer produces just as high an oxygen turnover as running, so is considered a ‘fitness equivalent’, but is associated with far fewer injuries.
However, analysis of the action of the cross trainer reveals that it doesn’t require much toe-pointing-style plantar flexion – the movement that increases the 90° angle between the front part of the foot and the shin – which would normally occur when you run. Therefore it may be worth doing additional toe-off-style work on the cross trainer and within your strength training regime.
The high-knee-lift effect is also minimal in the CT action, as you’re not attached to the paddle, so you tend to be passively lifting while the opposite leg is doing the work of pressing down. So try some single-leg cycling, which encourages the lifting phase of the pedal action with a passive dropping down of the leg on the downward part of each revolution.
How you use the CT is up to you and whether you want to keep it low impact or not. Some triathletes do turbo-plus-CT sets, allowing them to effectively practise the T2 effect in training. This is particularly useful for low-impact training, such as when niggles rear their head or after a hard mid-winter running race.
As it’s a fixed location option, use the normal tricks to keep you occupied such as listening to an MP3 player, thinking about technique, using the digital feedback that the CT provides and mixing in other cross-training activities. For example, 10mins turbo, 10mins CT, 10mins core work and so on.