The Lactate Step Test and Minimum Test for Cycling
Lactate testing for endurance performance has been around for decades and much has been learned about the testing methods and lactate itself. Lactate has a few important roles in the bloodstream, such as a buffer to lower higher PH’s, a messenger to other parts of the body and its part in creating ATP, the fuel muscle cells need (1). The lactate step test has been the go-to method for cyclists to help determine heart rate and power thresholds, but this test has been challenged in recent years. The definition of what a threshold is, regarding both power and heart rate, on top of everyone’s ability to clear lactate sums up some of the challenges to the test. The lactate minimum test is another lactate test and looks for a rise in lactate but in a different way, along with how you’re analyzing the test result.
The Step Test
The lactate step test puts an athlete through a graded exercise test starting at a low power output and ramping up power every 3-4 minutes, taking lactate values along the way, while looking for a rise in lactate somewhere around the 4 mmol mark. The result of this test is to determine where a cyclist can achieve steady power without increasing lactate concentrations. At or under this power level, lactate remains steady or falls but pedaling over the power level increases lactate levels. As you can see in this article by Iñigo San Millán, PhD, the 4mmol lactate “threshold” happens around 4.5-5 watts per KG with amateur cyclists and around 5-5.5 watts per KG with elites (2). While this test shows consistency across the board as far as how much power amateurs and elites can produce around 4mmols in lactate, it doesn’t represent where a cyclist is in respect to a 10-60 minute power threshold. Elites can put out 6-7 plus watts per kg for a 10–60-minute effort while top amateurs can produce around 5 - 6 watts per kg (3).
The step test is based on power and while it has its challenges, such as the difference between inflection points and actual critical power measurements, or the simple fact that everyone is different when it comes to clearing lactate and producing it, it has its benefits. Due to its consistency, you can track fatigue and over training when looking at power trends over time at the 4 mmol level, with increases and decreases in power (4). Learning how everyone responds to producing and clearing lactate is critical to testing consistency.
The Lactate Minimum Test
The lactate minimum test, also known as the balance point test, takes a cyclist through a maximal effort time trial to start, and begins taking lactate readings at the end of the time trial. The result of this test is closely related to heart rate values and therefore is best when looking for lactate inflections at a given heart rate. Typical first readings at the end of the time trail are high, usually in the 8-10 mmol range. Once the first reading is taken, the cyclist is directed to reduce intensity by 40 beats per minute, using power to maintain a steady state and steady heart rate for 3-5 minutes where a second reading is taken. Even though the cyclist is in a recovery state, spinning 40 beats less than the highest heart rate in the test, lactate values don’t drop fast, instead a typical lactate value will be 2-3 mmol less than the first reading. So, let’s say the first reading was 10 mmol, the second reading will be in the 7-8 mmol range.
The cyclist is then instructed to increase intensity by 10 heart rate beats and about 20-30 watts to achieve a higher steady state. Let’s say that after the time trail the heart rate was 170 BPM and 10 mmol of lactate, and the second reading was at 130 BPM and 8 mmol. The third lactate reading will now take place at 140 BPM after holding steady power and HR there for 3-5 minutes, and the typical trend is that you will continue to see a decrease in lactate values. There is significance to seeing lactate values fall while increasing intensity. Its tells you that your body is clearing it faster than you need to produce it.
As you go through each step, increasing heart rate by 5-10 beats per minute, you will eventually see an increase in lactate, representing at that point the body can no longer clear it faster than its produced. This is called the lactate minimum point. This inflection point coincides with a shift from primarily burning fat as fuel to burning blood sugars, glucose, and glycogen. This point will also represent at what point lactate remains in your system and not be cleared. The presence of lactate in your system has benefits, from lowering PH to creating ATP, but it also promotes the growth of mitochondrial density, the powerhouse of the cell (5). The greater the mitochondrial density, the more places for fuel and oxygen to be used, the more power you can produce. In essence, this inflection point shows you the minimum intensity needed to make mitochondrial gains, as well as the intensity where there is a shift in fuel used, regarding fat and blood sugar.
Minimum lactate test performed by a Highland Training Client
Each step had a steady state effort between 3-5 minutes.
Age – 55 years
Heart Rate Threshold – 170 BPM
Pre-Test Time Trial -10 minutes
1st reading at 10 min = 10.0 mmol at 169 heart rate & 350 watts. Average power for the 10 min TT = 328 watts.
2nd reading at 130 bpm = 8.8 mmol
3rd reading at 140 bpm = 4.5 mmol <- Increasing intensity but still clearing
4th reading at 150 bpm = 5.3 mmol <- Inflection point/increase in lactate
5th reading at 155 bpm = 7.0 mmol
6th reading at 160 bpm = 9.2 mmol
It’s important to realize that lactate and lactic acid are different, by one hydrogen ion (1). Your body produces lactate, not lactic acid, to help keep up with the energy demand. While the science behind lactate is still developing, we know the benefits of lactate. Knowing the minimum inflection point allows you to target an intensity that’s on the high end of aerobic metabolism, while focusing on increasing power production from your type 1 muscle fibers. Retesting this range over time to see power increases will relate to a bigger aerobic engine and the ability to work at a higher level while still primarily burning fat. Building aerobic power, which is usually the focus during the base season, will result in faster recovery and the ability to work harder more often, increasing power at your true 10–20-minute power thresholds on the bike. Its important to focus on the right energy systems at the right time of the season. Doing that will result in greater overall power gains.
Mike Schultz, CSCS
1 – “What is blood lactate and why is it important for exercise?” January.AI, Jan. 2022, https://www.january.ai/blog/what-is-blood-lactate-vs-lactic-acid
2 -San Millán, I. “What is Lactate and Lactate Threshold” Training Peaks Blog. https://www.trainingpeaks.com/blog/what-is-lactate-and-lactate-threshold/
3 – Coggan, A. “Creating Your Power Profile” Training Peaks Blog. https://www.trainingpeaks.com/blog/power-profiling/
4 – “Lactate Testing - Advanced Concepts” Lactate.com. https://lactate.com/pitesadv.html
5- Takahashi K, Kitaoka Y, Matsunaga Y, Hatta H. Effects of lactate administration on mitochondrial enzyme activity and monocarboxylate transporters in mouse skeletal muscle. Physiol Rep. 2019 Sep;7(17):e14224. doi: 10.14814/phy2.14224. PMID: 31512405; PMCID: PMC6739509.