Introduction

Among fighters, one very popular strategy to improve endurance is the use of a snorkel apparatus during training. Aiming to promote a systemic hypoxia, the snorkel strategy hypothetically induces oxygen uptake restriction and, therefore, partially desaturates the hemoglobin mass, promotes an increase in erythropoietin (EPO) production and release by the kidney, which is recognized by the bone marrow as a signal to increase hematopoiesis. Another hypothesis is that the oxygen restriction can increase blood acidosis by the increase of blood CO₂ concentration, since both oxygen uptake and CO₂ output are restricted. By controlling ventilation, the bicarbonate buffer is supposedly activated, and the anaerobic system would be more participative culminating in a higher lactate production and a lower glycemia. Since a lower O₂ volume was probably sent to the muscle in activity, the heart rate (HR) would to be higher to support the O₂ demand (for aerobic transition), that could be shown by a higher HR in the restricted group. Therefore, the aim of this study was to determine the effects of the snorkel strategy during maximal treadmill exercise on hemoglobin saturation, heart rate, lactate production and glycemia in Brazilian jiu-jitsu athletes.

Material and methods

Twelve healthy men participated in this study (age: 22.20 ± 4.20 years; weight: 69.52 ± 8.19 kg; height: 173.80 ± 3.08 cm), and they were all Brazilian jiu-jitsu athletes with at least 6 months of experience.

Athletes went twice to the laboratory. In the first time they performed the treadmill protocol without snorkel for control (CON), and after 7 days they performed the same protocol equipped with a snorkel apparatus (SNK). Participants remained 48 h without exercise before the test.

HR (Polar model RS800CX) and hemoglobin saturation (SpO₂) (pulse oximeter APK Tecnologi Co., Ltd, MD300) were collected every min from 5 min before to the end of the test, and subsequently every 5 min after the test (for 1 h). Time to exhaustion, maximum speed and distance were collected. Glycemia (On Call Plus, Acon Laboratories, Inc) and lactate (Lactate Plus, Nova Biomedical) data were collected from the fingertip pre (Pre), post (Post) and one hour post exercise (1 h post).

Data was treated in two different ways: (1) to compare groups the T Test for paired samples was selected; (2) for analysis between moments (Pre, Post and 1 h post) the ANOVA one way with Turkey’s post hoc was adopted. For these treatments the IBM SPSS Statistics 19 was used.

Results

Oxygen restriction promoted by snorkel resulted in a significant difference of performance between SNK and CON groups. The CON group performed 2156 (± 277.57) m during 13.60 (± 1.07) min at a pace of 15.60 (± 1.07) km/h, whereas SKN group showed lower results: 1270 (± 353.45) m during 10.60 (± 1.71) min at a pace of 12.20 (± 1.22) km/h.

There was a significant difference between groups at Pre, where the SNK group had a higher HR, and Post, where the SNK had a lower HR. SpO₂ was lower at Pre and Post for the SNK group.

Lactate levels increased from Pre to Post and decreased from Post to 1 h post for both groups. However, lactate concentration after the test was lower in SNK group. No difference was found in glycemia pre/post the treadmill test.

Discussion

Acute or chronic hypoxia protocols look very efficient to increase EPO synthesis, erythroide activity and hematocrit synthesis. Other authors have shown that acute exposure to hypoxia in a hypobaric chamber increases the EPO production after 114 min in a 3000 m altitude simulation or 84 min in 4000 m. A normobaric hypoxia seems to be efficient to increase the EPO synthesis after 240 min of exposure. A fourteen consecutive-day chronic hypoxia in a 5500 m simulated altitude is capable to increase erythroide activity, hematocrit and EPO synthesis. Higher EPO concentrations are apparently efficient for increasing oxygen uptake, and this efficiency in the aerobic metabolism is due to the positive stimulus from erythropoiesis that increases the oxygen transport to the muscles. Furthermore, the EPO is capable to cross the hematoencephalic barrier, decreasing central fatigue and increasing cognition. However, unfortunately, hypobaric chambers are not accessible for most athletes.

The Post-exercise HR difference between groups is justified by an earlier test interruption of SNK group, therefore, the SKN group was not able to achieve their maximum HR. Lorenço-Lima et al. reveled no difference in the HR between groups (Pre: 65.8 ± 9.2 and 74.4 ± 13.2 bpm; Post: 187.2 ± 9.25 and 189.8 ± 10.1 bpm; 1 h post: 85.8 ± 7.9 and 80.8 ± 10.2 bpm, CON and SNK respectively). The present study found higher HR Pre for SNK, lower Post for SNK, and similar 1 h post for both groups. Lorenço-Lima et al. did not show any difference on SpO₂ (Pre: 97.2 ± 1.3 and 97.8 ± 0.8 %; Post: 91.4 ± 2.5 and 90 ± 3.93 %; 1 h post: 97.6 ± 0.8 and 96.4 ± 1.5 %, CON and SNK respectively), which is different from the present where the SpO₂ was lower for SNK at Pre and Post, but not for 1 h post.

Lactate was also not changed between groups previously (Pre: 0.99 ± 0.07 and 0.98 ± 0.05 mmol/L; Post: 9.41 ± 1.35 and 9.09 ± 0.74 mmol/L; 1 h post: 1.00 ± 0.05 and 1.00 ± 0.04 mmol/L, CON and SNK respectively). In the present study lower lactate level for SNK was found Post compared to CON, having been justified by the lower performance of SNK.

Conclusion

It is possible to conclude that the snorkel implementation/air restriction promoted a higher hemoglobin desaturation even with a lower performance. Snorkel usage seems to be an accessible and cheap way to promote hypoxia. It suggests that it can be used as a good strategy during certain parts of a training periodization to keep the stimulus and decrease the body muscle damage promoted by high intensity training.