1. Why is triathlon training so focused around training volume?

Despite a growing body of literature points to mean training intensity over a season as the key factor for performance improvement, recreational endurance athletes (non-elite athletes) keep thinking `more is better´ and accumulate great training volumes at low or moderate intensities. A clear example for endurance sports was reported by Veronique Billat who showed that male Kenyan runners training at higher speeds had a significantly better 10-km performance than Kenyan athletes training at lower speeds, despite the elite status of both groups. To be honest, I do not know why but, from my own experience as coach and sport scientist, I can state that they feel more confident to face races and competitions when training with high volumes…let me assume that is due to the lack of knowledge about the importance of high-intensity training (HIT) for optimizing performance and the large correlation between high training volume and injury risk for endurance athletes.

2. What is the ideal training volume for a sprint triathlete?

One of the most important points you must take into account when prescribing training is `individualization´. There is no athletes with the same characteristics and, thereby, each one needs a personal plan. Increased participation in recreational and competitive triathlons over the last decade has been accompanied by an increase in the number of athletes sustaining injuries which indicates that athletes and coaches are doing something wrong. I really think that training volume plays a key role in the high rates of injuries and many studies support this rationale. Together with `individualisation´, the `progressive overload´ is another important point so that training volumes should vary over the sport season. These two factors make training volume different between endurance athletes even at recreational level (i.e., some triathletes perform 3-4 running sessions per week accumulating 25-30 km whilst others reach 50-60 km/week, with no significant differences in athletic performance).

3. Could you explain in general terms HIIT triathlon training?

Although there is no universal definition, high-intensity intermittent training (HIIT) generally refers to repeated short to long bouts of high-intensity exercise – performed at close to 100% maximal oxygen uptake (VO2max) – interspersed with recovery periods. As a training method that leads to a reduction in weekly training distances and an increase in mean training intensity without impairing athletic performance, high-intensity intermittent training HIIT is considered one of the most effective forms of exercise for improving the physical performance of athletes.

4. Could HIIT be applied to all three triathlon disciplines with success?

Without any doubt. In fact, elite swimmers, elite cyclists and elite runners are already doing it. HIIT takes part of their training routines. Nevertheless, we cannot forget that all triathlons are considered continuous endurance events and, long-distance sessions are also needed, in order to optimise performance. The answer is: How can coaches manage the use of both HIIT triathlon trainingand distance training methods? What we did in a just published study in the Journal of Strength and Conditioning Research, entitled “

A HIIT-based running plan improves athletic performance by improving muscle power” (García-Pinillos et al., 2016) was to increase the average intensity of the running plan (based on HIIT) whilst moderate-intensity but high-volumes sessions were performed for swimming and cycling. Why running? Because some previous studies indicate that most of injuries suffered by triathletes are running-related injuries and, are usually associated to high training volumes. The results obtained after 5 week of training were great and triathletes improved their athletic performance in 3-4%)

5. Should HIIT triathlon trainingbe cycled within training?

The HIIT protocol is well documented and various types of HIIT triathlon training programmes have been shown to improve endurance performance in swimmers, runners, cyclists and triathletes. In our studies, the inclusion of 2-3 HIIT sessions per week allows athletes to reduce training volumes and increase mean intensity, as well as to cause some positive effects on athletic performance.

6. How should strength or neuromuscular training complement HIIT? 

Either HIIT or resistance training (strength, neuromuscular training or plyometric training) are `training tools´ for coaches and should be included within training programmes of endurance athletes in any moment of the sport season. From a practical point of view, HIIT triathlon training complements resistance training and vice versa…all together, must let athletes increase their performance and keep healthy.

7. Is there a higher injury risk with HIIT?

This is a very interesting point. When coaches prescribe training programmes, they essentially pursue two objectives: (1) to improve athletic performance and (2) to avoid injuries so, these elements must be covered within any chat about training. The available information about the relationship between HIIT and injury risk is quite limited. More research in clearly needed about the effect of increasing average training intensity on injury risk at long term.
For example in running, despite the suggested association between increased running speed and running injury, none of previous studies have directly measured or monitored injury risk factors during HIIT intervention. Therefore, it seems that consensus exists about the benefits of HIIT interventions for endurance performance even though more longitudinal studies covering the effects of HIIT-based training programmes on injury risk-factors for endurance athletes are needed.

8. How should resting and taper alter with HIIT triathlon training?

Many variables can be manipulated to prescribe different HIIT sessions and among them, the intensity and duration of work and relief intervals are the key influencing factors. Then, the number of intervals and the number of series and between-series recovery durations and intensities determine the total work performed. The manipulation of each variable in isolation likely has a direct impact on metabolic, cardiopulmonary and/or neuromuscular responses. When more than one variable is manipulated simultaneously, responses are more difficult to predict, since the factors are inter-related, making it unclear which combination of work-interval duration and intensity, if any, is most effective at allowing an individual to spend prolonged time at VVO2max while ‘controlling’ for the level of anaerobic engagement and/or neuromuscular load.
The most important point in this answer is the `progressive overload´ principle. As we mentioned early, training periodisation should take the progressive overload principle into consideration. For example, during a traditional periodisation (increasing intensities and decreasing volumes) HIIT should move from long runs to shorter and faster runs, whilst sprint-interval training (SIT) should be progressively included from short sprints to 25–30 s all-out efforts.

9. Can HIIT be applied to longer distance triathlons (Olympic, Half, Full, Ultra)?  If so, when in the training process would you implement HIIT?

Despite these differences in distance and duration, all triathlons are considered continuous endurance events, requiring sustained metabolic work at intensities ranging from 80% to 55% of peak oxygen uptake for sprint and Ironman distances, respectively. Even thought training volumes are, obviously, higher for longer distance triathletes, the physiological basis and the training principles, are the same. In this context, what we should answer ourselves is what we know about HIIT and its effects on endurance athletes:

(a) HIIT-based training programmes are effective in improving athletic performance in endurance athletes;

(b) Exercise bouts at an intensity close to or above the intensity corresponding to VO2max appear to be more effective in improving performance and VO2max compared with moderate-intensity exercise training;
(c) HIIT-based training plans appear to be effective in improving `economy´ (O2 cost at a given pace) in trained endurance athletes;
(d) HIIT causes an increased oxidative capacity of a greater number of muscle fibers and a reduced plasma K+ concentration which contributes to the maintenance of muscle function during intense exercise and delays the apparition of fatigue.

Based on that, HIIT must be part of training plans for triathletes (longer and shorter distances). Finally, regarding when we can implement HIIT, the answer is ALWAYS. HIIT should be present during the whole season, at any moment but, as we earlier mentioned, the progressive overload principle must be taken into consideration