Unfortunately, there is no clear cut answer. In addition to the protocol that you mention, there is research that shows the other two combinations are also "optimal."
J Strength Cond Res. 2005 May;19(2):332-7.
Aerobic and resistance exercise sequence affects excess postexercise oxygen consumption.
Drummond MJ, Vehrs PR, Schaalje GB, Parcell AC.
Human Performance Research Center, Brigham Young University, Provo, Utah 84602, USA.
Excess postexercise oxygen consumption (EPOC) may describe the impact of previous exercise on energy metabolism. Ten males completed Resistance Only, Run Only, Resistance-Run, and Run-Resistance experimental conditions. Resistance exercise consisted of 7 lifts. Running consisted of 25 minutes of treadmill exercise. Vo(2) was determined during treadmill exercise and after each exercise treatment. Our findings indicated that treadmill exercise Vo(2) was significantly higher for Resistance-Run compared with Run-Resistance and Resistance Only at all time intervals. At 10 minutes postexercise, Vo(2) was greater for Resistance Only and Run-Resistance than for Resistance-Run. At 20 and 30 minutes, Vo(2) following Resistance Only was significantly greater than following Run Only. In conclusion, EPOC is greatest following Run-Resistance; however, treadmill exercise is more physiologically difficult following resistance exercise. Furthermore, the sequence of resistance and treadmill exercise influences EPOC, primarily because of the effects of resistance exercise rather than the exercise combination.
We recommend performing aerobic exercise before resistance exercise when combining them into 1 exercise session.
J Strength Cond Res. 2008 Sep;22(5):1487-502.
Concurrent training enhances athletes' strength, muscle endurance, and other measures.
Davis WJ, Wood DT, Andrews RG, Elkind LM, Davis WB.
Division of Physical and Biological Sciences and Strength and Conditioning Coach, Athletic Department, University of California at Santa Cruz, USA.
[email protected]
We evaluated the effects of concurrent strength and aerobic endurance training on muscle strength and endurance, body composition, and flexibility in female college athletes and compared two concurrent exercise (CE) protocols. Twenty-eight women (mean age, 19.6 years) were divided into two matched groups and evaluated before and after a vigorous, 11-week, 3-days per week CE training program. One group did serial CE consisting of a warm-up, resistance exercises at low heart rate (HR), aerobics, and a range of motion cool down. The other group did integrated CE consisting of aerobics, the same resistance exercises at high HR achieved by cardioacceleration before each set, and the same range of motion cool down. The two protocols were balanced, differing only in the timing and sequence of exercises. Serial CE produced discernible (p < 0.05) increases in lower- (17.2%) and upper- (19.0%) body muscle strength and fat-free mass (FFM) (1.8%) and trends toward greater lower-body muscle endurance (18.2%) and reduced upper-body flexibility (-160.4%). Integrated CE produced discernible increases in lower- (23.3%) and upper- (17.8%) body muscle strength, lower-body muscle endurance (27.8%), FFM (3.3%), and lower-body flexibility (8.4%) and a decline in fat mass (-4.5%) and percent body fat (-5.7%). Integrated CE produced discernibly larger gains than serial CE for six of nine training adaptations. Effect sizes were generally moderate (44.4% of discernible differences) to large (33.3%). We conclude that serial CE produces adaptations greater than those reported in the literature for single-mode (strength) training in athletes, whereas integrated CE produces discernibly greater gains than serial CE.
The results suggest synergy rather than interference between concurrent strength and aerobic endurance training, support prescription of CE under defined conditions, establish the importance of exercise timing and sequence for CE program outcomes, and document a highly effective athletic training protocol.
I agree with your assesment. For resistance work, I want to be as primed as possible to maximize the resistance session. If I'm worn down from 30-45 minutes of cardio prior to the resistance session, then I'm going to be in a suboptimal state. Also, my heart rate seems to elevate faster if I do cardio post-resistance work as opposed to when I do cardio work first thing. So, take your pick because the science definately isn't clear.
