Intensity vs Volume

Last winter I did a little n=1 experiment. I had not done a run of longer than 30 minutes for 3 months. Then, I proceded in this manner: I restricted myself to 2 to 3 30 minute interval-based (Zone 4/5) treadmill workouts per week for 6 weeks. I then did a 90 minute continuous Zone 2/3 run on the treadmill. The result was that I felt fine - no excess muscular or metabolic fatigue. Interestingly, the only 'new fatigue' was was found in my respiratory muscles of the ribs.

Here's a study recently released on the same subject:

From Xtri.com or PubMed

The major novel finding from the present study was that six sessions of either low volume SIT (short interval training) or traditional high volume ET (longer endurance training) induced similar improvements in muscle oxidative capacity, muscle buffering capacity and exercise performance. To our knowledge this is the first study to directly compare interval versus continuous training using a research design that matched groups with respect to exercise mode (cycling), training frequency (3 × per week) and training duration (2 weeks), but differed in terms of total training volume and time commitment. Several previous studies have examined muscle metabolic and/or performance adaptations to interval versus continuous training (Henriksson & Reitman, 1976; Saltin et al. 1976; Eddy et al. 1977; Fournier et al. 1982; Gorostiaga et al. 1991; Edge et al. 2006), but the data are equivocal and in all cases the total volume of work was similar between groups. The present study was unique because, by design, the total training volume for the SIT group was only ∼10% that of the ET group (i.e. 630 versus 6500 kJ). In addition, the total training time commitment over 2 weeks was ∼2.5 h for the SIT group (including the work intervals and the recovery periods between intervals), whereas the ET group performed continuous exercise each training day for a total of ∼10.5 h. Thus, while previously speculated by others (Coyle, 2005), to our knowledge this is the first study to demonstrate that SIT is indeed a very ‘time efficient’ training strategy.