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The Science of Performance |
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Running Physiology – The State of the Art Part 5 – VO2max or Running Speed? By Richard Gibbens In the first four parts of this review of the current state of the art of endurance physiology, we have examined the concepts of VO2max, lactate threshold, and running economy, their dominance in the world of exercise physiology, and the challenges against them. We continue now with a major question about VO2max and lactate threshold. That question is; does increasing my VO2max or lactate threshold allow me to run faster or does improving my running speed increase my VO2max and lactate threshold. For purposes of today’s discussion I am going to use VO2max to examine the question, but the principles and ideas apply equally to either concept. It seems like a simple enough question, but the answer is very important because it has been assumed by physiologists, coaches, and runners that increasing VO2max led to increases in running pace. Armed with that assumption, training programs have been created that have focused on increasing VO2max . For example, let’s say you have a VO2max of 65 ml/kg/min and a running pace at VO2max of 5:00 minutes per mile. Conventional wisdom says that if you increase your VO2max to 70 ml/kg/min, then your running pace at VO2max would increase also, say to 4:30 minutes per mile and your performance at any percentage of VO2max would also improve. What if the theory is wrong? What if it’s the other way around? What if, when you increase the pace at which you are capable of running, your VO2max increases too? If that is the case, then your training program should be designed to increase your running speed, with no consideration for your VO2max. Furthermore, a training program designed to improve your VO2max might improve your running speed (or it might not), but would it be optimal? It might improve your VO2max, yet cause little to no improvement in running speed. Now you see why the question I first posed is so important. Your entire training program is based on the answer to that question. I propose that increases in running speed lead to increases in VO2max. I base this on a couple of things. First, physiologists know that VO2max is relatively stable and changes little even with intense training.1 Second, it has been commonly observed that running performance can continue to improve even with no changes in VO2max.2 Third, studies have shown improvements in VO2max without any increase in running speed.3 These three facts taken together tell me that your focus should be on running speed, not VO2max. Two studies do an excellent job of illustrating my point.4 In 1982, at the University of California, researchers sprint trained rats. The workout consisted of 2 sets of 50 second sprints at a 15% gradient with 10 seconds of recovery between sprints. The workout was conducted 7 days a week for 4 weeks. At the end of the study the subjects had increased running speed 25% and had increased VO2max by 15%. Control groups had no increase in running speed or VO2max. The most amazing thing about this study was that the improvement in VO2max was accomplished without an increase in aerobic enzymes. Aerobic enzymes control the rate at which your muscles can process oxygen. More enzymes equal more oxygen processing capability. The rats in this study increased their rate of oxygen utilization without increasing their level of oxygen enzymes. How could that be? The answer is that the rats already had enough aerobic enzymes to support faster running. What they didn’t have were muscles strong enough to run faster. VO2max was not their limiting factor, their muscular system was. When their muscular system improved (25% increase), it drove up their VO2max (15%). In a previous study conducted by the same group, 10 weeks of steady endurance training upgraded aerobic enzymes by 100% and boosted VO2max by 14%. That’s impressive, isn’t it? But, this study failed to improve running speed. Even with a large 14% increase in VO2max, the rats were not capable of running any faster. These two studies provide compelling evidence that running speed drives VO2max and that the muscular system is the limiting factor in endurance performance. Now comes the most important part. Is your training program designed to improve your VO2max or your muscular system? If you perform any of the following types of workouts you are training to improve your VO2max and/or lactate threshold - tempo runs, cruise intervals, aerobic runs, base building runs, easy runs, or lactate threshold runs. Do you use a heart rate monitor in training? Do you attempt to run at some percentage of your max heart rate? If you do, then your program is designed to improve VO2max and lactate threshold. If you have come to believe that your muscular system is the limiting factor in performance, then you are probably wondering about the best way to train your muscles. We will scratch the surface of that question next time. Till then keep on running. References
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