Other than changing the mode or sport of your workouts, there are only three elements of training you can modify to build fitness: workout duration (how long), workout intensity (how hard), and workout frequency (how often). The combination of duration and frequency is called volume – how many hours, miles, kilojoules, or kilometres you train in a given period of time, such as a week. Athletes tend to become very fixed on this volume number thinking that it reveals the most important aspect of their training and ultimately determines how fit they are. Some times they are right.

There is no doubt that volume contributes to fitness. Try training only one day a week and see what happens to your capacity for exercise. In fact, early in the training year, as in the Base period, volume is quite beneficial. Racking up a lot of whatever it is that you like to measure from the list above will do wonders for your fitness. But the closer you get to your most important events the less beneficial volume becomes. In fact, it can actually decrease your race performance. In the last few weeks before your A-priority race, workout intensity and duration become the greatest determiners of how you will perform on race day. These need to take on the characteristics of the race itself. The days when you are not pushing the limits of intensity and duration you need to make easy. That essentially means cutting volume. Instead of riding two hours on a recovery day as you did in the Base period, you may now only ride for an hour - or even take the day off. Why? Because you need to be fresh and ready to push your limits of intensity and duration on the day of your next “breakthrough” workout.

By the late Build period at least one of your weekly workouts should take on the combined intensity and duration characteristics of your A race. You want the stress you experience in this workout to approach that which you will experience in the race. For most endurance-sport events, it’s unlikely that you will make this workout just as long and just as intense as the race. That’s likely to be far too demanding in terms of motivation and the number of days needed afterwards to recover before training hard again. But you can make it just as intense only shorter, or just as long only less intense. Intervals, repetitions and challenging workout segments can be included in workouts of different durations to simulate the stress of the race.

The bottom line is that you can’t have both volume and race specificity at the same time if you want to race well. Each requires too many resources. You can only have one or the other. In the Base period volume is very beneficial. But if you have an important race coming up in a few weeks, race specificity is the key to success.

- Joe Friel
The Training Bible

Before attempting to answer these questions, let's define the terms. Volume is the product of duration and frequency. Duration is how long a workout lasts. Frequency is how often workouts are done. Volume is usually expressed in terms of weekly accumulated training time or mileage. Intensity for the purpose of this discussion refers to training done at or above the anaerobic threshold (also sometimes called lactate threshold, ventilatory threshold, or functional threshold). Assuming that you are preparing for an event that takes about one hour or less to complete at a maximum sustainable effort, this intensity is about race intensity. For athletes competing in events that last longer than about one hour, training intensities at and above AT are more challenging than race effort. This is not to say that athletes training for longer events should not train above the AT. It is quite common, especially for elite and well-experienced athletes.

Let's get back to the original question: Will volume or intensity have a greater impact on your race performances? There is very little research on this matter, but what there is seems to be in agreement. Let’s examine two of these for some insight.

In a German study, 17 experienced runners steadily increased their volumes from their normal 50 miles per week to 105 miles per week over a four-week period (1). All of these runs were done at about marathon pace or slower (2mmol/L lactate). One year later they allowed the researchers to tinker with their training again. This time they nearly doubled the amount of time they trained at high intensity, over a four-week period again. With increased intensity they improved on four measures of performance from 5 percent to 17 percent. Increased volume produced no significant improvements in the same metrics.

In another study of swimmers conducted by David Costill, PhD at Ball State University, it was found that increasing swim training volume from three hours per day to four per day and increasing swim weekly workouts from five to six sessions provided no greater benefits than training 60 to 90 minutes per day for five days per week (2).

Does this mean you should keep your training volume low while jacking up intensity year round? Not at all. When you have been training with low volume and low intensity for some period of time, as when in the season-ending "transition" period, gradually increasing the stress load by boosting volume is probably a wise move (3,4). This will help to prevent injury by fortifying soft tissues before commencing with higher-intensity training later.

During the Base period it is common in the classic/linear periodization model to increase the volume of training while also much more gradually increasing the intensity. In Base 1 I have my athletes training a considerable amount in zone 2. In Base 2 they add training volume in zone 3. And by Base 3 they are also training in zone 4. This is typical for all of my clients regardless of the events for which they are training. In the Build period the training becomes increasingly specific to the demands of their first A-priority race of the season, especially the intensity of those workouts.

So what's the bottom line? The intensity of one's training is a better predictor of performance than the volume of training although some mix of both is necessary for success.

Joe Friel is the author of the Training Bible book series and the founder of Training Bible Coaching, Ultrafit and Training Peaks. He may be reached through the Training Bible website at www.trainingbible.com.

References

1. Lehmann, M., et al. 1996. Unaccustomed high-mileage vs intensity training-related changes in performance and serum amino acid levels. Int J Sports Med 17(3):187-192.
2. Costill, D.L., et al. 1991. Adaptations to swimming training: Influence of training volume. Med Sci Sports Exerc 23:371-377.
3. Gomes, P.S. and Y. Bhambhaniy. 1996. Time course changes and dissociation in VO2max at maximum and submaximum exercise levels as a result of training in males. Med Sci Sports Exerc 28(5):S81.
4. Fry, R.W., et al. 1992. Periodisation of training stress – a review. Can J Sport Sci 17:234-240.