Background: In altitude training for elite athletes, altitudes below
1700 m are generally known to have low physiological stimulation and training
effects. Therefore, the purpose of this study is to investigate the effect of
live high train high (LHTH) altitude training at an altitude of 1600 m on
athletic performance, complete blood count (CBC), and erythropoietin (EPO) in
cross-country skiers. Methods: In this study, South Korean Six male
cross-country skiers participated. Exercise performance, CBC, and EPO were
measured 3 days before altitude training and 4 days after the end of altitude
training. The training program in this study was the LHTH altitude training
method, and the polarized (POL) training program was applied. For exercise
performance analysis the Bruce protocol was applied using a treadmill and gas
analyzer. Blood variables CBC (red blood cell; RBC, white blood cell; WBC, hemoglobin; Hb, hematocrit; Hct, platelets) and EPO were
measured at rest and immediately after exercise. Results: The effect of
3 weeks of LHTH altitude training on male cross-country skiers was as follows.
There were no differences in body weight, muscle mass, body fat mass, or body fat
Cross-country skiing is the most complex endurance sport, as it competes with
both upper and lower body equipment in a cold environment, relatively high
altitude, and hilly terrain [1, 2]. World-class cross-country skiers who secured
the second position at the Winter Olympics and Nordic World Championships are
reported to be superior to national-level athletes in terms of maximum oxygen
Cross-country skiers use the LHTH method for three reasons: First, to prepare for important events such as the Winter Olympics and World Championships held at high altitudes, high-altitude adaptation training is essential. Second, by maximizing the physiological benefits of exposure to hypoxia at high altitudes, competitiveness in competitions held at sea level can be expected. Third, cross-country skiers need to increase their annual ski training time in the snow; however, due to the influence of the weather, the seasons and places where ski training can be conducted are limited. Low temperatures at altitudes have the advantage of enabling ski training in the snow earlier than in winter, thereby increasing the training rate for technical skills and physiological specificity [6, 20, 21].
In LHTH training, it is very important to set an appropriate altitude and period because the higher the altitude, the greater the negative physiological burden, whereas the lower the altitude, the lesser physiological stimulation. In general, 3–4 weeks are recommended for a settingsetitudeaining period. This is because changes in blood variables start 2 weeks after starting altitude training, increase significantly between 3 and 4 weeks, and then reach a plateau after 4 weeks [22, 23, 24, 25]. Although the optimal altitude for altitude training is 1500–3000 m, training at an altitude of 2000–3000 m is the most effective because physiological stimulation is insufficient at an altitude of less than 1700 m [26, 27, 28]. When perfor ming altitude training, the higher the altitude, the higher the rate of muscle injury caused by the cold. In addition, negative effects such as upper respiratory infection, immune suppression, sleep disturbance, and weight loss due to maladaptation to high altitude which can reduce exercise ability should not be overlooked [11, 29, 30]. In particular, cross-country skiers perform altitude training mainly in autumn and winter and are exposed to cold environments [6, 31]. Altitude training for cross-country skiers can improve ski training and physiology, but it is necessary to consider the relatively low altitude that can prevent the negative effect of cold.
Therefore, the purpose of this study is to investigate the effect of live high train high (LHTH) altitude training at an altitude of 1600 m on athletic performance, complete blood count (CBC), and erythropoietin (EPO) in cross-country skiers.
Six male cross country ski (XC) skiers over the age of 20 (21
|Age (yr)||High (cm)||Body mass (kg)||Muscle mass (kg)||Body fat mass (kg)||Body fat percentage (%)|
|n = 6||21
To analyze the effect of short-term altitude training on exercise performance, CBC, and erythropoietin, measurements were taken 3 days before altitude training and 4 days after the end of altitude training. This study was conducted for three weeks using the LHTH altitude training method. The base (village) elevation was 1609 m, and the ski training was performed at an elevation of approximately 1609–1915 m.
The altitude training program was planned by mixing the POL training program by Kim with Choi (2020) and the ski training program at the altitude by Choi (2018) [32, 33]. The altitude training applied a polarized (POL) training program most commonly used by world-class cross-country skiers. The POL training program is a training method that combines high-intensity interval training (approx. 12–15%) and a lot of exercise at low intensity (approx. 70–80% of the total amount of exercise). In addition, maintaining the same training intensity at sea level as training intensity can cause overtraining and immune suppression in athletes, so the amount of high-intensity training was reduced and applied at sea level [9, 32, 34, 35, 36, 37]. The total amount of exercise performed in this study was as follows: low-intensity training (LIT), 75.19%; medium-intensity training (MIT), 2.32%; high-intensity training (HIT), 6.2%; strength training, 11.62%; and running, 4.65% (Table 2).
|Day||AM training||PM training|
|Mon||Event||Ski training (skate)||Ski training (classic)|
|Time||100 min||40–40–30 min|
|(5 min (ex)/3 min (re) |
|Tue||Event||Ski training (classic)||Ski training (skate) + Weight training|
|Time||120 min||Ski 60 min (LIT) + W/T 60 min|
|Intensity||LIT||80% (1 RM) |
|recovery time 90 sec|
|Wed||Event||Ski training (skate)||REST|
|Thu||Event||Ski training (classic)||Ski training (skate)|
|Time||100 min||30–30–30 min|
|Fri||Event||Ski training (skate)||Weight Training + Core Training|
|Time||40–40–30 minute||90 min|
|(5 min (ex)/3 min (re)
|Intensity||LIT-HIT-LIT||80% (1 RM) |
|recovery time 90 sec|
|Sat||Event||Ski training (classic+skate)||REST|
|Intensity||Low intensity||Middle intensity||High intensity||Weight training||Other sports||Total|
|Exercise Time (minute)||970 min||30 min||80 min||150 min||60 min||1290 min|
|Training as a % Total volume||75.19%||2.32%||6.2%||11.62%||4.65%||100%|
|Section (1 week)||7||1||2||2||1||11|
|Weight event||65% (1 RM) |
|Bench press (put legs on the bench, not on the floor) & Pull-down|
|Triceps Pull Downs, DeadliftRowing/arm-pull while sitting & Arm-press with dumbbells using incline bench, Legs: Squats & hamstring curl, single-leg squat, side squat|
|Core training||Exercise 5 set, Recovery 30 sec|
|Supine plank, prone plank, side plank, side plank-leg motions statically, spine in a neutral position, Swiss ball training (inclined press-ups, the top position, the single-leg holds, quadruped motions)|
Exercise performance was measured 3 days before the altitude field training and
4 days after the end of training in consideration of the travel time from the
altitude camp to the laboratory. The Bruce protocol was applied for the exercise
load test using a treadmill and gas analyzer (COMED Quark CPET, Italy). After
starting at 1.7 mph at 10% of the initial incline, every 3 min, the incline was
increased to 2%, and the speed was increased from 0.8 to 0.9 mph so that the
treadmill speed could not be maintained, and the maximum heart rate was more than
90% of the target heart rate (THR). The respiratory exchange rate was 1.15 or
more, the movement awareness was
The test subjects fasted for more than 10 h from the measurement time, and blood was collected. After the subject arrived at the test site and rested for at least 30 min, the nurse collected 3 mL of blood at rest and immediately after exercise, appropriate for the purpose and procedure of the analysis. The collected blood was centrifuged (FLETAS, Korea) at 5000 rpm for 10 min and then analyzed.
CBC (RBC, WBC, Hb, Hct, platelet) and erythropoietin were diagnosed using flow cytometry, serum samples, and refrigerated storage. Reagents were analyzed with SYSMEX-XE2100D (SYSMEX, JAPAN) using the cell pack, cell sheath, stromatolyser-FB, and Sulforlyser kit .
We used SPSS software (v.25.0; IBM SPSS, New York, USA) to calculate the mean
value and standard deviation (SD) for all data. The verification of exercise
performance, CBC, and erythropoietin before and after altitude training in the
same group was analyzed using the paired t-test. Statistical
significance was set at p
Table 3 shows the changes in body composition when living at 1600 m and training
atana altitude for 3 weeks. There was no significant difference in body mass
|Variable||Pre test||Post test||p|
|Body mass (kg)||66.30
|Body muscle mass (kg)||34.21
|Body fat mass (kg)||6.48
|Body fat percentage (%)||9.73
|SD, standard deviation.|
Table 4 shows the changes in exercise performance when living at 1600 m and
training at altitude for a week. VO
|Variable||Pre test||Post test||p|
|Exercise time (second)||1135.16
|HRmax (heart rate maximum) (beats/min)||198.00
|RHR (Rest heart rate) (beats/min)||136.16
|SD, standard deviation. *p |
Table 5 shows the changes in CBC and EPO when living at 1600 m and training at an altitude for a week.
|Variable||Pre test||Post test||p|
|SD, standard deviation.|
RBC at rest was significantly increased afte (4.94
At rest, Hb was significantly increased after (15.73
At rest, Hct was significantly increased after (47.43
Body composition and cardiorespiratory function affect the health and exercise
performance of adult men, including endurance athletes. It is desirable to
maintain a low body fat percentage and a large amount of muscle mass [44, 45]. In
general, the VO
In the treadmill test, maximum exercise time was used to measure the speed and
performance of athletes. It is also a good method for monitoring physiological
factors such as VO
It has been reported that HRmax and resting heart rate are highly correlated
with age, sex, and physical fitness level. During exercise, VO
Cross-country skiers utilize primarily aerobic energy metabolism on flat
terrain. However, as the slope increases, the athlete’s heart rate rises to its
maximum level, which requires strong anaerobic power. To win the race, it is very
important to quickly recover the increased heart rate and lactic acid on the
uphill slope and the flat ground [28, 62, 63]. Also, quick physiological recovery
is important in team sprint competitions in which two skiers run the sprint
course three times in relay format [9, 41]. In general, a common method for
assessing the recovery capacity of cross-country skiers is heart rate monitoring.
It is evaluated as the rate at which the heart rate decreases from the maximum
heart rate level . The results of our study also confirmed that the heart
rate recovered quickly. As mentioned above, it is thought that blood variables
The human body increases the production of EPO in the kidneys to adapt to the low partial pressure and hypoxic environment at high altitudes, and RBC and Hb, which play a role in binding and transporting oxygen, also increase. On the other hand, inadequate training at altitude, insufficient iron stores in the body, and the presence of infection can negatively affect hematological parameters [65, 66]. It is known that EPO and Hb increase together with altitude training, but there are also reports that the correlation between EPO and Hb mass may be inconsistent due to individual variability [67, 68, 69]. Existing studies also reported that EPO, RBC, Hb, and Hct all increased with altitude training, and conflicting research results reported that EPO increased but RBC, Hb, and Hct did not change. The conflicting results in high-altitude training are due to differences in training altitude, training duration, and stay method [70, 71]. In addition, it should be taken into account that EPO, which increases due to exposure to hypoxia at high altitudes, remains elevated for 24–48 hours after sea level return, and then decreases sharply after 72 hours, returning to normal levels before training [72, 73]. In this study, RBC, Hb, and Hct increased due to altitude training, but the slight decrease in EPO was judged to be due to blood sampling and individual differences 92 hours after reaching sea level. Therefore, although EPO decreased slightly, RBC and Hb increased, suggesting that LHTH training at 1600 m may be recommended for male cross-country skiers.
It has been reported that RBC and Hb are highly correlated with improvement in
exercise performance, including VO
Exercise-induced leukocytosis refers to an increase in WBC immediately after exercise. Although there have been previous studies that the number of WBC decreased as a result of LHTH training, it is generally reported that the activation of white blood cells is increased by excessive exercise and high-intensity training rather than the effect of altitude [80, 81, 82]. Platelets play an important role in blood coagulation and hemostasis and living at altitude and vigorous exercise can increase the number of platelets, and excessive increase in the number of platelets can increase bleeding tendency or cause thromboembolism [83, 84]. Conversely, acute high-altitude exposure may decrease platelets but return to normal with a compensatory effect after short-term adaptation [85, 86]. Also, there is a study result that regular exercise of elite endurance athletes inhibits platelet adhesion and aggregation, and that the platelet count can decrease after vigorous exercise [87, 88, 89]. In this study, there was no difference in WBC and platelets at rest with altitude training, and the decrease immediately after exercise suggests that LHTH training at 1600 m for 3 weeks did not have a negative physiological effect on male cross-country skiers.
Combining our study, it was confirmed that RBC and Hb, which are factors that have an important influence on oxygen transport and cardiorespiratory health level, can be stimulated at a relatively low altitude of 1600 m. Therefore, it is thought that high-altitude training and living will have a positive effect on men’s health promotion by improving the function of blood factors related to oxygen use.
The results of this study suggested that 3 weeks of LHTH training at an altitude
of 1600 m could stimulate RBC, Hb, and Hct. Also, improved VO
For cross-country skiers, the higher the altitude, the better for training and physiological stimulation. Compared to previous LHTL studies, the implications of this study are that it was conducted at a lower altitude than typical altitude training. In this study, the effect of 3 weeks of LHTH training at 1600 m on hematology and exercise performance was confirmed. This means that even at 1600 m it can cause hypoxia. We acknowledge some research limitations that must be considered for data interpretation, and furthermore, practical recommendations should be limited to cross-country skiers and coaches. In particular, this study had a limitation in that there was no control group and only male athletes were targeted. Future studies will require more detailed studies of training altitude setting, training duration, training intensity, and training method using a large number of subjects and control groups. Nevertheless, what can suggest LHTH training at 1600 m to male cross-country skiers is that training at relatively low altitudes can experience similar performance benefits to training at high altitudes.
JCW and YCC designed the research study. JCW performed the research. KTY provided help and advice on YCC analyzed the data. JCW, KTY and YCC wrote the manuscript. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.
We obtained informed consent from all. Ethical approval for our study was obtained from the Institutional Review Board (IRB) of Gangneung-Wonju national university (approval number: GWNUIRB-2021-11), and all study procedures were in accordance with relevant guidelines.
This research received no external funding.
The authors declare no conflict of interest.
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