The Pros and Cons of Two-a-Day Training in Single Discipline Endurance Sports

What are the advantages and / or disadvantages to doing more than one training session a day for single discipline sports? Most recreational triathletes can prepare for their chosen events with one training session a day and the most common spread is two sessions per discipline per week plus a rest or strength day. As we become a bit more ambitious, we start to add sessions to the week and this necessitates some days having a morning and evening session. Many triathletes have become comfortable with this and the different demands that the three sports that make up triathlon place on our bodies make this doable for most. The question that we pose in the first sentence is aimed at single discipline endurance sports. Is there any benefit to training twice a day as a cyclist, runner or swimmer? Adding in one or two sessions of strength and mobility training a week, as a second session in the day, is probably beyond dispute and we are therefore not discussing that. What we want to know is, would doing a session on the bike or run in the evening, after we have already done one in the morning, be good, bad, or a waste of time?

The most important question that we need to ask ourselves before any training session is, why we are doing it and this is very relevant to this discussion as well. I think that multiple sessions a day would be most interesting to time-crunched athletes. I know that this may sound counterintuitive but hear me out. Most ambitious, recreational athletes who have work and family obligations have free time enough in their days for the training that they need to do to achieve their goals. What they may not have is significant blocks of time, all in one sitting. If we are training for a three to four hour bike race for example, we all understand that we need to build endurance and spend an appreciable amount of time on our bikes. School runs and early starts at the office might not allow us to go out for a two hour training ride before work but, we can probably get in a good hour before leaving for the daily commute and then another in the evening once the work day is done. Yes, there are adaptations that occur when we train for consecutive hours but, as long as we get one of these long rides in on the weekend, we can considerably add to our overall weekly volume with two or three ‘double days’ during the week during a critical period of training.

Even if we can get in the two hour session before work by setting that early alarm, the impact of the longer, intense session at the beginning of the day, takes a lot more out of us than an hour would. This can often lead to low enthusiasm and energy through the rest of the day, with a lack of productivity at work and less than ideal engagement with our loved ones after work. Those early starts are very rarely sustainable as well, whereas a couple of high-energy efforts in the morning and evening are psychologically and physically easier to accomplish and probably more productive as a result.

Another advantage of double session days is that we prolong the ‘after-glo’. When are finished a training session, our bodies continue to burn energy at higher rates. Our base metabolic rate is elevated when we finish training and only gradually returns to normal after an extended period of time. Doing another training session twelve hours later will kick that metabolic rate back up again and extend the amount of time we spend during the day, at an elevated rate. This has a number of advantages for the endurance athlete chiefly the fact that we will burn more calories and become leaner, improving the all-important, power/weight ratio. The increase in aerobic training volume in our days and weeks will also improve our bodies’ efficiency and how we utilise fats to fuel our exercise. Over time this allows us to train and race for longer as our bodies are able to utilise more fats in our muscles’ fuel mix, even at higher intensities.

The major disadvantage of two training sessions a day is the potential to over-train. Whereas a triathlete would do something along the lines of a bike ride in the morning and a swim in the evening, which target different muscle groups and could also be aimed at different energy systems and intensities, doing two sessions of the same discipline utilises the same muscles and the same motor-pattern. So, even a bike in the morning and a run in the evening by a triathlete, which obviously use the same muscles but in a different way, is potentially less physically draining than two bike rides or two runs which incorporate the same muscles in the same way. This is not necessarily a bad thing. The principle at the core of all training is that we need to stress our bodies in order to elicit adaption and improvement. The harm comes when we stress ourselves to far beyond what we can recover from before we do it again. So, the first rule of two-a-day training is, only start incorporating it when we are ready and then gradually add sessions as we start absorbing and adapting. Basically, exactly as we would do when starting any training after a period of low activity. Only this time, we are already well conditioned, we are just taking it up a notch.

So, now that we are sold on some potential advantages and fore-warned against the possible pitfalls of two-a-day training, how should these days be tackled? The most common method is one easy session and one hard session. Most like to do their higher intensity training in the morning when they are fresher but there has been research to indicate that we are actually more ready to go hard in the evening. It will depend on what the rest of our day looks like and how that will impact the evening session. There is another factor in support of the harder session in the morning and the easier second session. Training hard only a few hours before bedtime can result in poor sleep patterns and even insomnia. This will then have a trickle down effect for the sessions that follow as recovery relies on good sleep.

Not all our days need to follow that hard/easy combination though. There has been research to indicate that there are benefits to starting a hard, interval session in the evening on tired legs. The key hard efforts in a race usually happen towards the end, on tired legs. It would therefore seem logical to train ourselves to push to those high levels in an already fatigued state. Even if the advantage is mostly psychological, it is still and advantage.

As in more conventional once-a-day training schedules, the intensity of each session is determined more by where the particular block of training fits into our overall progression and what we are training for. The intensity mix should move from prominently zone one and two in the early weeks where both our morning and evening session can be aerobic, steady-state sessions to our final peak weeks where the morning session could be a threshold session with a lot of zone four effort and we smash out some VO2 efforts in the evening.

The key is to treat the week as a whole, just as you would a seven session week, only now we are potentially looking at ten or eleven sessions. Fitting a particular workout into the weekly mix or micro-cycle, depends on our current level of conditioning, what we are trying to achieve with the week’s training and then what we are doing with the sessions on either side. Whether they are on the same day or the next day, doesn’t matter as much.