Biomechanics and Medicine in Swimming XI

BiomechanicsandmedicineinswimmingXi
Estimation Method for Energy Expenditure by
Acceleration of Human Head during Water Walking
Kaneda, K. 1 , ohgi, Y. 2 , tanaka, c. 3
1 Research Fellow of the Japan Society for the Promotion of Science, Japan
2 Keio University, Japan
3 J. F. Oberlin University, Japan
This study aimed at estimating energy expenditure (EE) by accelerations
of human head during water walking (WW). Fifty Japanese males (n =
29, age: 27 to 73) and females (n = 21, age: 33 to 70) participated in this
study. They conducted WW at three walking speeds of 25 m/min, 30 m/
min and 35 m/min. During the WW, an accelerometer was attached to
the occipital region of the subjects and recorded three-dimensional accelerations
at 100 Hz. We developed estimation equation for EE (kcal/
min/kg) including three components of the resting metabolic rate, internal
energy expenditure for moving his/her body and energy expenditure
against for water drag force. The correlation coefficients were high in
both males (r = 0.79) and females (r = 0.77). theoretical estimation equations
for EE during WW was developed.
Key words: energy expenditure, estimation, Accelerometer, Water
Walking
IntroductIon
There are many studies and devices estimating energy expenditure (EE)
during land walking, jogging or daily life activities (Kumahara et al.,
2004; Scott et al., 2006; Tanaka et al., 2007). Due to its availability, those
studies mostly used accelerometers attached to human body (e.g. waist,
wrist and ankle). They reported good estimation explained by high correlation
coefficient (Scott et al., 2006). However, those studies and devices
cannot apply to water exercise because water has specific characteristics
compared to air, most prominently water resistance and buoyancy.
During exercising in water, the gravitational stress at the lower extremity
joint is reduced and greater exert force required for moving (Miyoshi et
al., 2005). The metabolic responses during water exercise were different
from exercise on land (Masumoto et al., 2008). Until now, we investigated
metabolic responses during water walking (WW) for a wide range
of Japanese males and females, and cleared that the metabolic responses
during the WW were influenced by mostly the walking speed other than
the human body size and sex (Kaneda et al., 2009a). Therefore, it is important
to develop specific estimation equation for EE during WW for
health promotion water exercise. The hypothesis was that the energy
expenditure during walking in water was estimated by three components
of the resting metabolic rate, internal energy expenditure for moving
his/her body and energy expenditure against for water drag force. We
tried to develop estimation equations for EE by accelerations of human ¾
head during WW, and this study introduces these methodologies. The
future goal is to develop an underwater activity monitor by using an
accelerometer.
Methods
Fifty Japanese males (n = 29, age: 27 to 73) and females (n = 21, age:
33 to 70) participated in this study. The mean characteristics of the subjects
are shown in Table 1. They provided a written informed consent
to participate in this study, and their health status was examined from
screening of medical history and measured blood pressure before each
subject’s experiment. This study was approved by the Ethics Committee
of Shonan-Fujisawa Campus at Keio University.
The subjects conducted WW at three walking speeds of 25 m/min,
30 m/min and 35 m/min (some subjects executed from 20 m/min ¾ and
¾
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40 m/min depending on their physical condition), and exercised over 5
minutes at each walking speed. In order to maintain the walking speed
steady, a pace-maker walked with the subject on the pool-side. The each
waking trial was separated by more than 5 minutes rest period to recover
the subject’s condition. The experiment was carried out at the indoor
swimming pool (17.2 m length, 5 m width and 1.1 m depth) (Figure 1).
During the each exercise bout, an accelerometer was attached onto
the occipital region of the subject and recorded three-dimensional accelerations
at 100Hz. The metabolic responses (VO 2 , l/min/kg and VCO 2,
l/min/kg) were measured by the Douglas bag method using a portable
gas analyzer (AR-1 O2-ro, Arcosystem Inc., Japan) and a dry gas meter
(DCDA-2C-M, Shinagawa Corp., Japan). Furthermore interval times
between mid 15 m by stopwatch were also measured at the each bout.
All analyzed data were selected from last 2 round trips of the each walking
trial. The energy expenditure (EE, kcal/min/kg) was calculated by
following equation (Weir, 1949) for developing estimation equation
from acceleration data:
EE (kcal/min/kg) = 3.9 × VO 2 (l/min/kg) + 1.1 ×VCO 2 (l/min/kg) (1)
Table 1. Characteristics of the subjects, mean±SD.
Age (yr) Height (cm) Weight (kg) BMI
Male (n = 29) 55.0 ± 14.9 170.9 ± 6.1 69.2 ± 9.0 23.7 ± 3.0
Female (n = 21) 57.4 ± 10.7 156.8 ± 4.6 54.2 ± 5.6 22.1 ± 2.6
Fig. 1. Pool condition in this study.
results
A total of 160 samples (males: 97 samples, females: 63 samples) were
obtained and used for analysis. We considered three components in the
estimation equation for the EE (kcal/min/kg): resting metabolic rate
(RMR, kcal/min/kg), internal energy expenditure for moving his/her
body (joint energy expenditure: EE j ) and energy expenditure for water
drag force (EE wd ):
EE(kcal /min/kg) = α 0 + α 1 RMR + α 2 EE j + α 3 EE wd (2)
The RMR was calculated by sex, age and weight based on the basal
metabolic rate (BMR) equations in the Dietary Reference Intakes for
Japanese (Ministry of Health, Labour and Welfare, Japan, 2010) and
multiplied 1.2 for the RMR by Numagiri et al. (1970):
RMR(
kcal / min/ kg ) = BMR(
kcal / min/ kg ) × 1.
2
The EEj was assumed to the square root of the sum of squared of both
the sagittal ( Ay') and vertical ( A z ′ ) accelerations. For eliminating gravity
effect, the acceleration data was corrected by head inclination angle
(Figure 2):
A ¾ z ′ = Az − gcosϑ ¾
(4)
Ay'= Ay − gsinϑ (5)
(3)