Hyperventilating into an uncomfortable facemask while someone in plastic gloves pricks your finger is like a rite of passage for many endurance athletes. It’s one of the truest signs that you’re taking your training seriously, enduring several minutes of pain and a sore finger to unlock the secrets of your physiology.
But testing is expensive, painful, and for many people, it can be hard to find a good testing provider or lab. And now that on-the-road tests and software paired with power meters and GPS watches can accurately estimate our FTP, do we really need to go to all that trouble?
“I almost never measure any physiological variables. It’s very hard to draw any correlation between that and improvement in performance,” said Paulo Saldanha, an exercise physiologist who coaches cyclist Michael Woods, the 2018 Road World Championships bronze medalist. Saldanha used to rely on the lab, but now favors on-the-road tests. Sometimes he gets his best numbers simply by having his athletes race one another. As Saldanha sees it, the ultimate goal of testing is to estimate potential performance, but no artificial lab protocol estimates it as well as actual performance.
Jared Berg, an experienced physiologist who ran the physiology lab at the University of Colorado Sports Medicine and Performance Center, agrees that “when you’re doing [on-the-road] testing, you’re really looking at how well you perform.” But he adds “[with lab testing] we’re looking inside the physiology to see how you’re doing that performance.”
To use a metaphor, with on-the-road testing, you can see how the car races but you can’t actually look under the hood. Getting the athlete into the lab, hooking up the ventilator, and measuring their lactates shows how the engine works.
The Three Goals of Physiological Testing
Whether you are testing on the road or in the lab, the first and most important goal of testing is to see how the athlete performs.
According to Berg, there are two other goals:
- Testing is very helpful at determining both training zones and strengths/weaknesses.
- Testing allows the athlete to track physiological improvements over time.
The advantage of lab testing is that it can show what energy systems the athlete is using, how much of that energy is coming from fat or carbohydrates, and when they are relying on slow-twitch vs fast-twitch fibers. On-the-road testing can only guess at these important details.
Let’s take a deep dive into the different types of testing available and how to know you’re getting good value for your money.
The VO2max Test
The VO2max test has been the standard protocol in research for decades. The subject wears a mask connected to a metabolic cart that measures gas exchange—which is a fancy way of saying it measures oxygen consumed and carbon dioxide exhaled.
The goal of a VO2max test is to determine an athlete’s maximal oxygen consumption, commonly referred to as their VO2max. Despite measuring only two variables and having a single endpoint focus, a surprising amount of data can be learned from a good VO2max test:
- An athlete’s aerobic and anaerobic thresholds—referred to as ventilatory threshold 1 (VT1) and ventilatory threshold 2 (VT2)
- Fat and carbohydrate utilization
- Delta and gross efficiency, just to name a few. [1–3]
During a VO2max test, a cyclist pedals on an ergometer or smart trainer that steadily increases power approximately every minute until failure (they can’t maintain power), or their oxygen consumption plateaus. Gas exchange, heart rate, power, and perceived exertion are all measured.
How to get good testing data from a VO2max test
- The protocol should increase power in small increments every minute or less.
- To determine that true VO2max has been achieved, oxygen consumption should plateau (though that’s not always the case in elite athletes).
- Another key end criteria for a VO2max test is the respiratory exchange ratio (RER): the ratio of carbon dioxide exhaled to oxygen consumed. It should start around 0.80 and by the end of the test it should exceed 1.0. Ideally, it should reach as high as 1.1 or 1.15.  Just bear in mind that some athletes get nervous and hyperventilate before and the test starts to artificially drive up the RER for the first minute or two.
- Starting wattage and increments should be individualized so that the test lasts between 12 and 15 minutes. If the test goes longer, the athlete may fatigue before they reach a true VO2max plateau. Conversely, if it is too short, the intensity may get too hard too quickly and again, they will not reach a true VO2max.
A 2007 study in Sports Medicine pointed out that while VO2max testing is common, it actually has limited application for athletes because it doesn’t really accomplish any of the three goals mentioned above.  First, VO2max power is not effective for determining training zones. Second, training doesn’t really improve VO2max in anyone except beginner athletes. [5,6]
Most importantly, VO2max has been shown to correlate poorly with performance. A big reason for this is because there are two key attributes that play into how well an athlete can use oxygen:
- The athlete’s ability to deliver oxygen to their muscles (in other words, their VO2max).
- The effectiveness with which an athlete’s muscles can use that oxygen, also called efficiency.
An athlete can have a very high VO2max but perform poorly because they can’t use that oxygen efficiently. Conversely, they can have a lower VO2max, but still perform well because they are very efficient with the oxygen they get.
Finally, Berg pointed out that the VO2max protocol itself doesn’t really approximate racing: “When in sport do you just increase your intensity every minute until you fail?”
The Lactate or Ramp Test
Unlike the VO2max test, a lactate test is designed primarily to determine an athlete’s submaximal parameters or thresholds. Arguably, a lactate test does a better job predicting these key variables. The test also provides an athlete’s lactate profile (see Figure 2), which can tell a lot about how well an athlete can sustain various intensities, including providing insights into how they metabolically accomplish the workload. 
The lactate test protocol
Like the VO2max test, power is increased at regular intervals, but the stages are much longer in a lactate test (anywhere from three to 10 minutes). Blood lactates are measured at the end of every stage by pricking the athlete’s finger or ear and taking a small blood sample. The test ends when the athlete can no longer continue, at which point a final blood sample is taken. Heart rate, power, perceived exertion, and blood lactate concentrations are all measured.
Some physiologists will measure gas exchange during a lactate test as well. The ratio of oxygen to carbon dioxide tells a lot about how the athlete is using fuels at the various intensities. An RER of 0.7 means they are burning entirely fats, an RER of 1.0 means all carbohydrates, and 0.85 means a 50:50 mix. “When lactates are low and fats are high, we’ll know that the athlete is using type I [i.e., slow-twitch] muscle fibers,” says Berg.
The final result is a lactate curve (Figure 2). In a good lactate curve, lactate levels will start below 1 mmol/L and remain there for several stages. When the athlete reaches their aerobic threshold (AeT, the equivalent of VT1) the line will start to curve upwards and exceed 2 mmol/L.
Some physiologists believe that the lactate or anaerobic threshold (AnT, the equivalent of VT2) occurs when the athlete reaches 4 mmol/L. However, this benchmark has generally been thrown out due to high individual variance. An experienced physiologist looks at the shape of the curve to determine the anaerobic threshold. How that’s done is beyond the scope of this article, but there are valuable resources and studies explaining the methodology. [7,8]
How to get good testing data from a lactate test
Proper stage lengths and power increments are crucial. How the protocol is designed can be the difference between accurate and misleading results, according to Ciaran O’Grady Ph.D., sports scientist and coach for Israel–Premier Tech. He recommends that if you go to a physiologist for a ramp test, you ask about their protocol, and more importantly, ask for any research backing that protocol.
At sub-threshold intensities, blood lactate levels should level off with each stage of the test, but often it takes minutes for that plateau to occur. If the stage is too short, the lactate concentration measured at the end of the stage may be misleadingly low if they hadn’t plateaued yet. Likewise, if the power increases too much with each stage, the athlete may not complete enough stages to draw an accurate lactate curve.
- Three-minute stages are the shortest length you can get away with, according to O’Grady. Berg prefers five minutes or longer for elite athletes—up to 10 minutes for some elite cyclists.
- Power increments are generally around 20-30 watts or 0.25-0.5 w/kg.
- The athlete should complete between six and nine stages if an effective protocol was used. If they complete too few stages, they won’t get a good lactate curve. Too many stages, and they may fatigue before reaching threshold.
- The starting power should be low enough so that the first two or three stages show no increase in lactate concentrations.
- The final one or two stages should exceed 4 mmol/L.
- The lactate monitor can be a limiting factor, according to O’Grady. Ideally, a testing lab uses a desktop analyzer, although in recent years, handheld monitors such as Lactate Pro are catching up.
- For cyclists whose primary goal is to determine training zones, they should perform the test on their own bike hooked up to an ergometer or smart trainer. Your power meter may not be as accurate as the professional SRM bike in the lab, but that doesn’t matter for training purposes. If they differ by 25 watts and the physiologist gives you threshold values and zones based on the SRM bike, you’re not going to be able to train effectively.
Berg recommends focusing on the physiology and not the watts because testing is not just about proving how strong you are. It’s about learning your physiology. He also recommends correlating your heart rate with your key physiological markers so that you can effectively target your training.
The Hybrid VO2max and Lactate Test
It is possible to combine the VO2max test with a lactate test. The athlete starts by doing a standard lactate test while connected to the metabolic cart so that gas exchange can be measured. Once the physiologist determines that the athlete has reached their anaerobic threshold, the physiologist will switch to a VO2max protocol, and continue until oxygen consumption plateaus.
Note: The hybrid test can generally only be completed by cyclists with a high fitness level. It can also under-measure VO2max.
Preparing for Physiological Testing
No matter what protocol you’re using, it’s important to prepare effectively. Here are a few tips:
- Top off the tank! Be sure to restock your glycogen levels because muscle glycogen can impact both lactate levels and your gas exchange. Make sure you eat sufficient carbohydrates in the days leading up to the test. But avoid eating any simple sugars in the hour before the test, which can also skew the results.
- Treat it like a race. Do your standard race prep the day before and arrive rested.
 Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they? Sports Medicine Auckl N Z 2009;39:469–90. https://doi.org/10.2165/00007256-200939060-00003.
 KEIR DA, FONTANA FY, ROBERTSON TC, MURIAS JM, PATERSON DH, KOWALCHUK JM, et al. Exercise Intensity Thresholds: Identifying the Boundaries of Sustainable Performance. Medicine Sci Sports Exerc 2015;47:1932–40. https://doi.org/10.1249/mss.0000000000000613.
 Bentley DJ, Newell J, Bishop D. Incremental Exercise Test Design and Analysis. Sports Med 2007;37:575–86. https://doi.org/10.2165/00007256-200737070-00002.
 Edvardsen E, Hem E, Anderssen SA. End Criteria for Reaching Maximal Oxygen Uptake Must Be Strict and Adjusted to Sex and Age: A Cross-Sectional Study. Plos One 2014;9:e85276. https://doi.org/10.1371/journal.pone.0085276.
 Lucía A, Hoyos J, Chicharro JL. Physiology of Professional Road Cycling. Sports Med 2001;31:325–37. https://doi.org/10.2165/00007256-200131050-00004.
 LUCÍA A, HOYOS J, SANTALLA A, PÉREZ M, CHICHARRO JL. Kinetics of VO2 in professional cyclists. Med Sci Sport Exer 2002;34:320–5. https://doi.org/10.1097/00005768-200202000-00021.
 Maunder E, Seiler S, Mildenhall MJ, Kilding AE, Plews DJ. The Importance of ‘Durability’ in the Physiological Profiling of Endurance Athletes. Sports Med. 2021 Aug;51(8):1619-1628. https://doi.org/10.1007/s40279-021-01459-0
 Jamnick NA, Botella J, Pyne DB, Bishop DJ. Manipulating graded exercise test variables affects the validity of the lactate threshold and [Formula: see text]. Plos One 2018;13:e0199794. https://doi.org/10.1371/journal.pone.0199794.