The Truth About Runner’s Fatigue


Japan’s latest experiment reveals the truth about marathon runner’s fatigue.

A few days ago, a runner sent a screenshot of his marathon pace per kilometre from a marathon race to Stamina Sports. The enigma of this runner is that although he has a uniform pace throughout the whole marathon race, his heart rate was constantly increasing. The longer the distance, the increase of tiredness was felt. He was seeking if his issue could be helped? Let’s take a look at the data screenshot.

Due to the massive crowd of runners at the first km, he could only attain a pace of 7 mins plus. His remaining race was maintained at a pace of around 6 min plus. However, his heart rate has increased from the initial of 145bpm to the max of 162 bpm.

The first 21km: The runner’s body remained in a less fatigue state. His muscular endurance can support the body’s activity. Thereby, maintaining his heart rate of around 145 bpm and delivering enough oxygen to the muscles.

The second 21km: The runner gets tired. Although the total activity intensity has not changed, the “relative intensity” has increased and the previous heart rate level can no longer support the oxygen supply to the muscles. Therefore, to maintain pace, the body will cause the heart to pump faster and thus increasing the heart rate.

Lactic Acid – The main culprit

During the second half of the race, the reason of the increase of runner’s heart rate and fatigue level was due to accumulation of lactic acid in the body. When lactic acid reaches a certain concentration, our body will feel tired and persistent increase in concentration will collapse the body’s motor function.



What is lactic acid? When we exercise, the glycogen in our blood will convert into energy. This process is divided into 3 phases: “aerobic combustion”, “aerobic and anaerobic mixed combustion” and “anaerobic combustion”.

Runner’s heart rate and pace chart

Let us analyse the heart rate data of the runner above.

In the first 19km, the heart rate of runner is 145 – 152bpm. At this time, the body of the runner is mainly in the state of “aerobic combustion”. Most of the glycogen will be completely burned into water and energy. The amount of lactic acid produced is relatively very little and insignificant.

At 20km – 32km, the runner’s heart rate is between 149 – 158bpm. The body of the runner is now in the state of both “aerobic energy supply” and “anaerobic energy supply”. This is where an increased of lactic acid begins. Here, a portion of the body’s glycogen turns into lactic acid instead of energy.

Why me? Why can’t my Glycogen fully be converted into energy but lactic acid?

After 32km, the heart rate of the runner peaked at 158 – 162bpm range. His body changed from “aerobic energy supply” and “anaerobic energy supply” to solely “anaerobic energy supply” state where his body’s glycogen converts mostly to lactic acid instead of energy output. Therefore, the accumulation of lactic acid is accelerated and eventually elevated.

After analysing the heart rate, we found that the runner’s body has experienced three phases of lactic acid production – the least amount of lactic acid, the small amount of lactic acid and a large amount of lactic acid . Let’s summarise these lactic acid concentration phases.


Let’s examine the accumulation of lactic acid

The concentration of lactic acid in the blood is corelates to the degree of fatigue of the human body . As shown in the figure, when the concentration of lactic acid in the blood is less than 2 mmol/L, the body is in a state of very little lactic acid and there is no feeling of fatigue. When at 2mmol/L – 4mmol/L, the body produces a small amount of lactic acid and begins to feel tired. When the threshold point of 4mmol/L and beyond is reached, the body’s lactic acid concentration rises rapidly. Here, large amounts of lactic acid will be accumulated in the human body which will cause the heart rate to increase. This will exhaust the body resulting in the drop of pace during the 2nd half of the marathon.

Runner: Got to rid this harmful lactic acid from my body


α-carnosine to helps depletes lactic acid

Mr. Yasuda Hiroshi, a professor researching “lactic acid” at the University of Tokyo’s Graduate School of Sports Physiology has studied lactic acid and its related knowledge for his lifetime and holds an annual global “lactic acid conference” in February.

The method of Hiroshi is plain and simple: consume “α-carnosine”! Hiroshi recruited five professional running instructors from Tokyo to take “α-carnosine”. Each must run 3 minutes at the treadmill for 7 times and is divided into taking “α-carnosine” and placebo. This test measures the concentration of lactic acid in relation of exercise intensity level.

Experiments have shown that by taking “α-carnosine”, the lactic acid concentration in the blood would be significantly reduced. This indicates that “α-carnosine” effectively breaks down the accumulated lactic acid in the body and successfully converts lactic acid into energy, which is then recycled and utilized by the body.

Findings: “α-carnosine” user

  1. Running at the same pace, produce lesser lactic acid.
  2. At the same level of fatigue, runner could run faster.
  3. At the same pace and the same level of fatigue, runner could run further.

“α-carnosine” Katsuo Stamina – Run Faster, Finish Stronger

Reference: Japan Run+Trail Magazine Report[/vc_column_text][/vc_column][/vc_row][vc_row content_width=”grid”][vc_column][vc_empty_space height=”17px”][mkd_button size=”” type=”outline” hover_type=”” target=”_self” icon_pack=”” font_weight=”” text=”揭秘跑马疲劳真相” link=””][/vc_column][/vc_row]