Testing the machine at full power
I’M NOT SURE what possessed me to sign up for a VO2 max test at the University of Guelph recently. Curiosity? Fascination with numbers? Vanity? Nothing better to do at 5 pm on a Thursday after a sedentary day at the office?
The ostensible purpose was to gradually take my system from easy to flat out, all the while measuring my heart rate, my air intake and my oxygen consumption. The test was offered as a Ride to Conquer Cancer fundraiser by Hilary, an employee in the Human Nutraceutical research lab at U of G, with assistance from Matt, a PhD student in the same department (none of us pictured here, as I forgot to bring my camera!).
Hilary started with the easy stuff – measuring my weight and height, then determining my exact body composition through a painless electrical impedence test. (Apparently, I’m nearly 66 per cent water – slightly higher than normal – my body fat is 16 per cent, and I have a BMI of 20 – both normal.)
Then it was on to the VO2 max lab. Know what the term means? Neither did I, or not precisely. I knew it was supposed to measure the peak of my ability. That by the end of a 5K race I’m at VO2 max – the peak volume of oxygen my body can process – not only through rapid breathing, but also by pumping blood and delivering it to my working muscles. So how were they going to measure that?
Turns out, it wasn’t all that complicated. They simply put me on a stationary bike, plug my nostrils, make me breathe through a snorkel-type device so they can measure the air coming in and the carbon dioxide and oxygen going out, monitor my heart rate, then gradually increase my pedalling workload in one-minute intervals until I can do no more. Bingo – VO2 max!
So I’m sitting on the bike all hooked up and bursting to get underway. I’ve signed the waivers in case I never return. Across from me sit Matt and Hilary. They’re starring at a laptop filled with my data, and have a magic button at their disposal – the one that makes my peddling get harder. I wish I’d brought my camera, because this is one goofy looking setup.
Off we go. It’s hard not to peddle too fast for the first 6 minutes or so, because there’s so little resistance. This is the warm-up I guess. I aim to stablize my cadence at a rate that feels comfortable, something I can maintain when the going gets harder. At first I can’t even detect the change in workload when Matt says, “I’m increasing now.” I just peddle and enjoy the ride, even though there’s no scenery, and the two of them are chatting quietly to themselves. I can’t hear anything except the air rushing through the heavy tube that’s stuck to my face.
At about 10 minutes, I start to feel it. It’s like I’m climbing a hill – okay at first, but I’m having to concentrate for sure. I look down, then up, and stare at the only numbers I can see – my heart rate displayed in front of me: 150 beats per minute, and gradually climbing. I know that when I run I can eventually reach 180, but doubt this is possible on the bike, in a closed environment.
Each time Matt ups the workload, he urges me on. “Come on, give it everything you’ve got,” he says.
I don’t think so Matt. This is getting harder, but I’m not giving it everything just yet. I’ll save that for later. At 12 minutes, I know can do another one, and maybe two or three. I look only at the floor now, except for quick glances at the cadence monitor, which registers a steady 90 RPM. Heart rate is gradually climbing of course. 167, 168 … then into the 170s.
Towards the end of 13 minutes Matt seems ecstatic. “You can do another one, yes you can,” he says with a raised voice. Yeah no problem. Except my legs are feeling heavy for the first time and I’m sucking air through the tube as hard as I can. I push into 14-minute territory. “Give it everything …” – yeah, I know Matt, I am. Flat out. The resistance feels like it’s increasing every five seconds, coming at me like a big wave. I struggle, swaying from side to side in the saddle. I’m not going to crack 15, I realize.
Matt and Hillary see something on their laptop and quickly signal me, “Okay, that’s it.” I’m relieved to stop, not that my pedals were moving much anyway. It’s like someone suddenly poured cement into my quads and my cadence dropped in half just like that.
Hilary is there in an instant, removing the darn head gear. Matt has dialed the bike resistance way back and my feet spin freely. Hilary puts a water bottle in my hand and urges me to cool down with easy riding for a few minutes. I’m bursting with sweat. My hearing is distorted. Gradually, my breathing recovers, and in five minutes I’m back more or less to normal. (I’ll have that super-relaxed, post-max hangover for several hours, like I do after a hard race).
• • • • •
The feeling at VO2 max is a familiar one, even though I’ve never reached it on a stationary bike before. It’s not just the physical exhaustion that comes from maxing out your effort. It’s also the mental urge to surrender, which is overwhelming. In a race, you can sustain that for a minute or two, but not much longer. So, you want to time your effort carefully to reach it very near the end.
The test was meant to find three very specific numbers:
- VO2 max: the oxygen I process at my peak, expressed as a relative number: volume of O2 per kilogram of body weight (so that the measurement is a constant between people of different sizes)
- Max heart rate: crudely, this can be guessed as 220 minus your age, but it varies from individual to individual, and can only be truly determined by a test like VO2 max
- AT: a subtler measurement known as Anaerobic Threshold – the heart rate where I stop producing energy aerobically and switch to anerobic
VO2 max Matt shows me a complex set of graphs and numbers, then gives me my result: 63 (that’s millilitres of oxygen per minute, per kilogram of body weight). I am unaware of what this means, but he says it confirms that I’m a fit and experienced runner. I have to look it up later to gauge where I fit in the range of humanity. A Tour de France cyclist might be in the 80s. Cross-country skiers, occasionally in the 90s. Sedentary males my age: about 35. To stand at the top of Everest without perishing immediately, 50-plus is required. I also find a chart that has VO2 max of 50 as “superior” – for a 20-year-old. For my age, a VO2 max of 40–45 is considered “excellent.” (Okay, I’m trying not to sound smug here.)
Max heart rate By the end of the test, my heart rate was at 180, which confirmed what I know from running. A few weeks earlier I’d tried my first spinning class, and anything over 165 felt like hard work, so reaching that on a bike was no easy matter. Max heart rate is related to VO2 max, because the rate your heart pumps plus the volume of blood it moves have a lot to do with your peak power, whether you’re biking, running, swimming or whatever.
Aerobic Threshold Matt pinpoints this at a heart rate of 170. He explains that not only is this the point where the body throws off lactate acid in order to produce energy with a shortage of oxygen. The lactate also generates additional CO2 – in excess of what is already accumulating due to the workload. So, there’s a sudden change in his VO2 measurements, which pinpoints the AT. This is very useful for training and racing – by wearing a monitor I can see my heart rate as I run, and use it as another input for judging my running pace.
All in all, it was a bizarre test – both simple (work until you can’t do any more) and complex (how exactly does that machine measure the oxygen and VO2 coming out of my mouth?). I’ll probably never do it again. What would be the point? My heart rate is gradually decreasing now, perhaps by a beat or so every two years. My VO2 max will show a corresponding decrease (and my running will get slower).
I won’t change a thing in my training – continuing the weekly running workouts that stress VO2 max and keep my fitness as good as it can be, for my age. And test my ability periodically in races and full-out efforts. It’s not exactly fun, but it does give me a strange and inexplicable sense of satisfaction. Call it beating the clock, in more ways than one.