From my time as a coached athlete, from observing other coaches to experimenting with varied approaches one thing is clear. Anyone serious about finding the best balance with their training should work with a Triathlon Coach who oversees all three disciplines for the athlete.
Athletes who use speciality coaches, such as a cycle coach for their riding, and a separate run coach for their running are less likely to strike a healthy balance with their training load. Single sport coaches are more likely to emphasise the discipline they specialise in, which sometime can be detriment to the other two disciplines if there isn't overall co-ordination. This mostly comes down to where their passion and area of expertise lies.
Tri Coaches see triathlon as one sport with three closely related disciplines, and this is reflected in their approach to training and strategies within the race. An example of a coach who may not see the sport in the same light is one who doesn’t believe running off the bike in training is of any importance.
In my view as a triathlon coach, during specific phases closest to an event, bike to run sessions are essential to helping athletes develop the ability to find their running rhythm and form quickly following the bike leg. They condition the body to adapt more quickly from a tucked bike position to the upright running stance.
There are many ways to structure such sessions. For example, if a long more intense bike ride is the key aim for the session, make the run immediately after easy with the purpose of hitting your rhythm and stride early, or vice versa. In this case the run should be relatively short, say 20-30mins.
How to plan training load between disciplines over a period
There are a number of different approaches to this question.
There is the blanket approach of continued even balance swim, bike and run training over a period, but that doesn’t account for individual strengths and weaknesses. Then there is loading up one discipline over a given period, but this generally requires that the others take a back seat during this time to ensure continued adaptation.
Whatever the approach, a coach should thoroughly research your past training history, results, and strengths and weaknesses prior to going down a path of training for you.
Then there is the goal itself, be it a short sprint, a draft legal Olympic, or even an ironman event. Each event lends itself to areas of speciality, such as draft legal racing with more of a swim/run emphasis. A coaches understanding and practical experience of how you can achieve the best result in your ARace is essential.
Finally, the period of time you allocate to train for your goal race is critical. The longer the block, the more latitude you will have to strategize within the periodised plan.
Essentially each phase of a periodised plan builds and prepares you for the next one. Knowing the important training components you need to concentrate on in each phase is the key. I.e. Phase 1 - may be all about building aerobic fitness and condition, Phase 2 – strength and aerobic capacity, and the final phase could be speed and speed endurance.
It could be likened to a jigsaw puzzle, once you know the important components it’s a matter of allocating adequate adaptation time required for each, and then slotting them into your training block.
It’s a balancing act, but that’s the nature of multisport.