Can We Predict Blood Lactate Change Non-invasively during

Treadmill Exercise?

Study on Wearable Near Infrared Spectroscopy (NIRS) System

Madoka Yamazaki

and Hideo Eda

Department of Health Science, Daito Bunka University, 560 Iwadono, Higashimatsuyama, Saitama, Japan

Department of Medical Photonics, The Graduate School for the Creation of New Photonics Industries, 1955-1

Kurematsu, Nishi-ku, Hamamatsu, Shizuoka 431-1202, Japan

Keywords: Blood Lactate, Wearable, Nirs, Treadmill, Exercise.

Abstract: Hemoglobin parameters by Wearable Near Infrared Spectroscopy (NIRS) were calculated and compared with

the simultaneously recorded blood lactate during treadmill testing. They showed a certain changes associated

with the exercise.

1 INTRODUCTION

Blood lactate during exercise has been commonly

used to evaluate the training effect and its intensities

and to predict the performance endurance in sports

laboratories (Bourdon, 2000), (Faude, 2009),

(Beneke, 2011). Especially blood lactate threshold

and maximal lactate steady state power are highly

correlated with the maximum aerobic power and

athletic endurance performance. Near Infrared

Spectroscopy (NIRS) calculates hemoglobin

parameters such as changes in oxygenated

hemoglobin (oxyHb) and deoxygenetaed hemoglobin

(deoxyHb). It is well known that oxyHb decreases

and deoxyHb increases during exersice (Homma,

1996). Now the system has become smaller, and

Wearable NIRS has developed (Eda, 2014). Purpose

of this study is investigating whether Wearable NIRS

can predict the blood lactate change non-invasively.

2 METHODS

Seven track athletes ( male / female : 5 / 2, mean age

20yr, height 166.5 cm, weight 58 kg) and non athletes

( male / female : 3 / 4, mean age 21.4yr, height 163.3

cm, weight 57.6 kg). All subjects were otherwise

healthy and had no history of heart vascular disease

and provided written informed consent. The

experiment was conducted in accordance with the

ethical guidelines of the Declaration of Helsinki, and

was reviewed and approved by the Research Ethics

Committee of Daito Bunka University (K15-001).

Subjects performed treadmill testing (Aeromill,

STM-2000, NIHON KOHDEN, Japan) using Bruce

protocol. Predicted peak heart rate was calculated as

220 − age. Subjects were encouraged to exercise until

85% of maximum predicted heart rate was achieved.

During the exercise and recovery stage, cuff blood

pressure, heart rate, cardiac rhythm (Mason-Likar

lead system) were recorded. Finger prick blood

samples (0.5μl) were taken every 3-5 minutes in the

right fingers and measured the blood lactate

concentration by using Lactate Pro TM (ArkrayTM,

Kyoto, JAPAN). Wearable NIRS was attached the

left index finger fixed with medical tape during the

exercise. The NIRS calculates haemoglobin

parameters We estimated the tissue oxygen level by

the Hb parameters.

3 RESULTS

The treadmill exercise duration was from 697 to 1048

(mean 921) seconds in athletes and from 451 to 784

(mean 627) seconds in non- athletes. The athlete’s

treadmill exercise duration was significantly longer

than non-athletes.

Blood lactate concentration increased in

association with the intensity of the exercise in all

subjects (Figure1 A, B). The changes of the blood

Yamazaki, M. and Eda, H..

Can We Predict Blood Lactate Change Non-invasively during Treadmill Exercise? - Study on Wearable Near Infrared Spectroscopy (NIRS) System.

lactate was from 2.3 to 8.7 (mean 5.1 mmol/l) in the

athletes and from 3.0 to 6.1 (mean 4.8 mmol/l) in the

non-athletes. There was no significant differences

between two groups.

Figure 1: Blood lactate concentration during the exercise.

A: case Athlete FS, B: case Non-athlete GT Arrow showed

the end time point of the exercise.

Oxy Hb showed a certain changes associated

with the exercise. Its pattern was divided into

decreasing (4/7 athlete, 3/7 non-athlete : Figure 2A),

increasing (2/7 athlete, 3/7 non-athlete : Figure 2B)

and no tendency (1/7 athlete ,1/7 non-athlete) pattern.

Deoxy Hb showed no exercise-specific change.

Figure 2: Hb parameters during the exercise

A: case Athlete FS. B: case Non-athlete GT.

Arrow showed the end time point of the exercise.

4 DISCUSSION

We investigated whether if NIRS can capture the

dynamic body signal change which related with blood

lactate concentration as the Hb parameters (oxyHb

and deoxyHb) during the treadmill exercise. Our Hb

parameter results recorded from the fingertip showed

no obvious relation between the changing rate of

blood lactate concentration and the Hb parameters.

Dynamics of the lactate is complicated which not

only released but absorbed at the same time and the

lactate clearance is different between the individuals

(Faude 2009).

There have been several studies which evaluated

the Hb parameter changing for the local skeletal

muscle by using NIRS (Hamaoka 1992, Homma,

1996, Boushel 1998, Celie 2012). They reported that

decreased oxyHb reflected the exercise intensity and

metabolic rate. In this study, we may capture the

results of dynamical changes which affected the Hb

oxidation or deoxydation throughout the body as we

attached NIRS module on the finger not on the

skeletal muscle related with the treadmill exercise.

Our wearable NIRS has advantages for

monitoring the physiological changes sampled from

everywhere in the body non-invasively. There has

several problems for the feature studies. We need

further evaluations whether if the Hb parameters

differ in the sampling location and cautions for

interpreting the dynamic changing of the Hb

parameters. However this wearable NIRS has

potential to be an easy use, non-invasive and portable

whole body sampling device which can capture the

physiological changes.

ACKNOWLEDGEMENTS

This research was supported by Genial Light.co.,

LTD, Hamamatsu, Japan and ALPS ELECTRIC CO.,

LTD, Tokyo, Japan

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