41

Bulletin of Glaciological Research ,- (,**0) .+ῌ.3
῎Japanese Society of Snow and Ice

Di#erences in cardio-respiratory responses to snow shovelingand shovel performance between elderly males and females
Isao MORITA+, Akihiko YAMAGUCHI, and Tsutomu SUDA+ School of Nursing and Social Services, Health Sciences University of Hokkaido, Kanazawa, Ishikari-Tobetsu, Hokkaido *0+ῌ*,3Japan, Department of Integrated Human Sciences, School of Dentistry, Health Sciences University of Kanazawa, Ishikari-Tobetsu,
Hokkaido *0+ῌ*,3- Japan- Graduate School of Education, Hokkaido University, Sapporo, Hokkaido *0*ῌ*2++ Japan(Received August ,3, ,**/; Revised manuscript accepted November 2, ,**/)

Abstract
The purpose of this study is to elucidate the di#erences in cardio-respiratory responses to snow
shoveling and shoveling performance between elderly males and females. Eight elderly males (EM, 0+
ῌ03, mean῍standard errors; 0../῍+.* yr) and ﬁve elderly females (EF, 0+ῌ1/, 01.2῍,.1 yr) who arehabitually engaged in manual snow removal performed +* minutes to ῍remove + m width at *.. m depth
using a snow shovel. Heart rate, volume of oxygen consumption (VO,), blood pressure, ratings ofperceived exertion (RPE), and productive variables including
shovel rate, shovel load and snow mass῍were measured. Signiﬁcant di#erences were observed in VO, (+.13῍*.*1 vs +.,*῍*.*0 Lῌminῌ+, p῏*.**+) and metabolic equivalent (2.,῍*./ vs 0.0῍*.- Mets, p῏*.*/) between EM and EF.
Cardio-respiratory responses were somewhat higher for EM than EF, as revealed by the heart rate(+/2῍/ vs +/*῍1 beatsῌminῌ+, ns), systolic blood pressure (+2-῍+* vs +12῍1 mmHg, ns), diastolicblood pressure (3/῍. vs 2.῍2 mmHg, ns) and RPE (+..3῍*.1 vs +-.0῍*.., ns), respectively. The large
di#erence in snow mass (++/῍+2 vs 03῍3 kgῌminῌ+, p῏*.**+) between EM and EF is considered to bea#ected by shovel load (++..῍,.* vs ..3῍*., kg, p῏*.**+), not by shovel rate (+*.-῍,.- vs +..*῍+.3
scoopsῌminῌ+, p῏*.*/). Volume of oxygen consumption῍ in terms of absolute value (Lῌminῌ+)
correlated with snow mass higher (r῎*.2-,) than relative VO, in terms of relative value (r῎*.0+0).
It was concluded that snow shoveling is strenuous exercise for the elderly and that elderly
females are less productive due to their smaller body size and lower physical resources.

+.

Introduction

About half the areas of Japan is covered withsnow during winter. Sapporo, a city in the northernmost island of Japan, has an annual cumulative snowfall of up to ﬁve meters. Such heavy snowfall occurs incities in cold regions such as Montreal, Edmonton,
Toronto, Stockholm, Minneapolis, and Harbin. Residents in Hokkaido are required to engage in the physically demanding task of snow removal every snowfall. The strenuous nature of snow shoveling has been
noted previously, due to death after blizzard causedby heart attack during snow shoveling (Rogot andPadget, +310; Glass and Zack, +313), risk of falls fromrooftops (Pipas et al., ,**,), and excess demand on
cardiovascular function (Suda et al., +33*; Sheldahl etal., +33,, +33-; Smolander et al., +33/; Franklin et al.,+33/, +330). Heavy snow shoveling elicits myocardial

infarction and aerobic demands that rival maximal
treadmill and arm-ergometer testing in sedentary men(Franklin et al., +33/). Moreover, since the amount ofsnow to be removed varies greatly depending on theweather, it is di$culty to adjust the desirable level ofhealth, in terms of intensity, duration or frequency of
exercise as recommended by the American College ofSports Medicine (ACSM, ,***). Physical resources required for snow shoveling are important determinants of independency for elderly people who have nosupport from their family or community.
Since snow shoveling consists of repeated exertion of the lift-and-throw motion at various shovel
loads, shoveling performance as measured by thesnow mass of lift-and throw is a#ected largely byphysical resources such as gender, body size, muscular strength, muscular power, aerobic capacity, shoveling skill, mental factors, shovel design, and the nature of snow.

42

Bulletin of Glaciological Research

Reduction in muscle strength, muscular power,
endurance in elderly people may be reﬂected in inferiority in snow shoveling performance. There are few
studies on the physiological responses to manualsnow removal in adult male subjects. Moreover, these
papers pay little attention to the inter-relationshipamong physiological responses, shoveling productivity and the physical resources of the subjects.
Therefore, it is necessary to clarify the relationship between physical resources and shoveling productivity. The purpose of this study was to elucidate
the physiological responses to snow shoveling in elderly males and females and to clarify the interrelationship among physiological responses, shoveling performance and physical resources in the elderly.

,.

Methods

Subjects
Eight elderly males (EM, 0+ῌ03, 0../ῌ+.* yr) and /elderly females (EF, 0+ῌ1/, 01.2ῌ,.1 yr), living in Sapporo and the surrounding communities volunteered
to be subjects in this study. None of the subjects had
functional disorder or cardiovascular disease andwere accustomed to manual snow clearing during
their daily works. The mean (SE) height and weight of
the EM were +00.+ (+.2) cm and 0-./ (,.3) kg, respectively, and those of the EF were +/+., (,.2) cm and /,..
(-..) kg, respectively. All of the subjects gave informed
written consent for participation in this study after
receiving a complete written and verbal explanationof the proposed measures and purpose of the investigation. The ethical protocol for the study was approved by the Ethics Committee for Human Investigation of the Graduate School of Education in Hokkaido
University.
,.+.

,.,. Measurements,.,.+. Physical resources
Before the experiment, physical ﬁtness test andshovel power test were performed to assess the physical resources of the two groups. Physical ﬁtness tests,
including grip strength (muscle strength), sit-andreach (trunk ﬂexibility), sit-ups (muscle endurance oftrunk) and 0-minutes walking test (endurance) wereselected as suitable because these tests were developed by the Japanese Ministry of Education, Culture,
Sports, Science and Technology (,**,), which werecommonly performed for a wide range of the Japaneseelderly population. In addition, based from the ﬁndings that back strength and leg extensor power correlated highly with shoveling throw distance (Morita
et al., ,**,), back strength (muscle strength) and leg
extensor power tests (leg power) were performed.
(+) Grip strength
Maximal grip strength was measured using a grip
strength dynamometer (Takei, model T.K.K. /.*+, To-kyo, Japan). Each subject held the dynamometer inline with the forearm at the level of the thigh and was
instructed to squeeze with maximal force. Two attempts were made with each hand, with the best scorebeing recorded. The scores for the right and left hands
were summed to provide a single index of strength.
Before the measurement, the dynamometer was calibrated by using a Dynamo-calibrator (Takei, Tokyo,
Japan).
(,) Sit and reach
Each subject sat on the ﬂoor with his back andhead against a wall and with legs fully extended. The
subject’s legs were inserted in a ﬂex meter (Takei,
model T.K.K/++,, Tokyo, Japan) at a height of -* cm.
The subject grasped the edge with both hands andslid the ﬂex meter. The arms were then stretchedforward while keeping the head and back against thewall at the starting position. The subject then ﬂexed
one’s trunk forward to push the ﬂex meter as far as
possible. Subjects were required to keep the ﬂex meterat the farthest position. The test was repeated twice
and the best distance was recorded.
(-) Sit-ups
Each subject lay on a mat in the supine position
with knees bent at 3*῍. The subject’s feet were held by
the examiner during the test. The subject’s arms were
folded across the chest with hands on opposite shoulders. The subject performed a full sit-up to the uprightposition with their elbows touching their thighs andthen returned to the down position with their scapulae in contact with the surface of the mat. The score
was based on the number of times the subjects reached the frame in -* sec.
(.) Six-minute walking distanceEndurance was assessed using a 0-minute walking distance (Guyatt et al., +32/). The subjects wereasked to walk over a // m course for 0 minutes.
(/) Back strength
Maximal back strength was measured using aback muscle dynamometer (Takei, model T.K.K./.*,
Tokyo, Japan). Each subject stood on the plate of a
dynamometer in the straight knee position with his
upper body bent at -*῍ grasping the handle bar withboth hands. The subject was then instructed to pullwith maximal force with their knees remaining extended. Two attempts were made with the best scorebeing recorded. Before the measurement, the dynamometer was calibrated by using a Dynamo-calibrator(Takei, Tokyo, Japan).
(0) Leg extensor power
Leg extensor power (Figure ,) was measured using an leg power system (Combi, Anaero Press -/**,
Japan) in a sitting position. Each subject used a chairwith a seat belt. In the starting position, the subject’s
feet were placed on a sliding plate with the knee angle
adjusted to 3* degrees. Each subject was advised tovigorously extend one’s leg opposing to braking load

Morita et al.

43

To assess the reliability of the shovel power test, .
-week test-retest measurements were conducted by ,*elderly males and +/ elderly females. The mean values(SE) and correlations between the ﬁrst and second
measurements in the shoveling throw ability were 0.0(+.0) m vs 0./ (+..) m, (ns) and r῏*.3, ( pῐ*.**+) in males
and ... (+.+) m vs ..- (+.*) m (ns) and r῏*.3, (pῐ*.**+) infemales, respectively.

Fig. +. Measurement of cardio-respiratory responses
to snow shoveling and productivity variables inelderly subject.

Fig.,.

Measurement of leg extensor power.

adjusted to the same load as one’s body weight. Fivetrials were performed at +/-s intervals, and the meanof the two highest recorded power outputs (watts) was
taken as the deﬁnitive measurement (Hirano et al.,+33.).
(1) Shoveling throw ability
Shoveling throw ability (Morita et al., ,**,) was
performed to evaluate the horizontal distance in snow
shoveling. Each subject was asked to throw a / kg
sandbag (-*῍,/ cm, Sakai Medical Instrument Co. Tokyo, Japan) in males and a . kg sandbag (-*῍,/ cm,
Sakai Medical Instrument Co. Tokyo, Japan) using asnow shovel (+.. kg in weight, *.10 m in shaft length,+-.. cm, in the blade area, Sekisui Co.). The greater
horizontal distance in two trials was recorded. The
weight of the shovel load at EM was based on theﬁndings that the optimum load of snow shoveling for
adult Japanese males is / kg (Furukawa, +30-), that theoxygen cost of a shoveling task is lowest at a shovel
load of / kg (Müller and Karrasch, +3/0), and that the
average value of shovel load during snow shoveling
was about / kg for adult males and about . kg for
adult females (Suda et al., +33*; Sheldahl et al., +33,).

,.,.,. Productivity variables
Snow shoveling performance was determined by
the amount of snow (snow mass) thrown onto a vinyl
sheet over a period of . minutes and was expressed askgῌminῌ+. The shovel rate (scoopῌminῌ+) was expressed as the number of scoops per minute. The
shovel load (kg) was expressed as the weight of snow
per scoop of shoveling (shovel load῏snow mass῎
shovel rate).
,.,.-. Cardio-respiratory responses῍῍Cardio-respiratory
variables (VO,, VCO,, and min῍
ute ventilation: VE), heart rate, blood pressure, andratings of perceived exertion (Borg, +31*) were measured at rest, during +* minutes of snow shoveling, andduring the recovery period. A portable expiratory gas
analyzer (VO,***, Medical Graphics Co., Minnesota,
USA) was used to measure
respiratory variables. Oxy῍
gen consumption (VO,) duringsnow shoveling is ῍ex῍pressed here as absolute VO, ῍(Lῌminῌ+), relative VO,(mLῌkgῌminῌ+,῏absolute VO, /body῍ weight) andmetabolic equivalents (Mets῏relative VO, /-./). One
metabolic equivalent equals -./ mLῌkgῌminῌ+. For
example, oxygen consumption during level walking
at 2* mῌmin is estimatedas +, mLῌkgῌminῌ+ in῍
terms of relative VO,. This value corresponds to -./Mets (῏+,/-./) in terms of metabolic equivalent and,in the case of a subject with a body weight of 0*῍kg,
corresponds to *.1, Lῌminῌ+ in terms of absolute VO,(῏0*῍+,῏1,* mL/min῏*.1, Lῌminῌ+). (Ainsworth,,***).
Heart rate was recorded from an electrocardiogram (ECG) using an ambulatory ECG recorder (Holter Co., DMC--,/,). Ratings of perceived exertion(RPE) were assessed using the Borg ,*-point scale(Borg, +31*) Blood pressure measurement was performed at rest and immediately after work using an
automatic sphygmomanometer (Omron, HEM1+.C,
Japan).
,.,... Experimental condition
Subjects wore the same clothing as their usual
wear and rubber boots for snow removal in theirhome. To assess the physiological responses to snow
shoveling and productivity variables, subjects were
instructed to repetitively lift-throw snow onto a vinyl
sheet from *.. m depth and + m width of snow layer
cleared at a self-paced rate using a lightweight alumi-

44

Bulletin of Glaciological Research

Table +.

Physical characteristics and ﬁtness of the subjects.

Age (years)
Height (cm)Weight (kg)
Grip strength (kg)Sit-and-reach (cm)Sit-ups (times)
Back strength (kg)Leg extension power (watt)
0-minutes walk distance (m)Shoveling throw ability (m)EM (n῏2)

EF (n῏/)p-value

0.4/῎+4*+004+῎+42
0-4.῎,43-34-῎+4,-04-῎,4+04+῎,4,+,34-῎++4++3+῎0*
1*2῎+314-῎*4/0142῎,41+/+4,῎,42/,4.῎-4.
,-4/῎+43-242῎-42+,4,῎*40
2,4,῎/40/3῎+**0,*῎+2.41῎*4.

*4+20
*4***
*4*.*
*4***
*4//1
*4+2.
*4***
*4***
*4*++
*4****

Values are means (S.E). .* Shovel load at shoveling throw ability were / kgin man and . kg in women.

Table ,. Comparison in cardio-respiratory responses during snow
shoveling between EM and EF.

RPEHeart rate (beatsῌmin῍+)῍VO, (Lῌmin῍+)῍VO, (mLῌkgῌmin῍+)
Mets
Systolic B.P. (mmHg)
Diastolic B.P. (mmHg)

EM (n῏2)

EF (n῏/)p-value+.43῎*41+/142῎/4*+413῎*4+,240῎+40
24,῎*4/+2-4.῎340
3.43῎-41+-40῎*4.
+.343῎04/+4,*῎*4+,-4*῎+4*040῎*4+124*῎041
2-40῎142

*4+23
*4-/0
*4***
*4*,3
*4*,3
*4030
*4+01

Values are means (S.E).

num shovel (+., kg, Sekisui Co. Tokyo, Japan) for aperiod of +* minutes. Before the work periods, thehard crust of the snow surface was broken up andhomogenized. The density of snow was measured
with a snow density sampler standardized by theJapanese Society of Snow and Ice (+33+). Mean (῎SE)
snow density was *.-,῎*.+ gῌcm-. During the testdays, air temperature and humidity varied from ῍, toῌ.ῑ and from ,, to 02῎, respectively.
,.,./. Statistical analysis
Results are expressed as means῎standard errors(m῎SE). A student’s t-test was used to determine any
signiﬁcant di#erence between sexes in the subjects’
physical characteristics and other measurement values. Relationships between variables of interest were
determined using Pearson’s correlation coe$cient.
Di#erences were considered signiﬁcant if pῐ*.*/.

-.

Results

Physical resources
Signiﬁcant di#erences were observed in height,
weight, grip strength, back strength, 0-minutes walking distance and leg extensor power between EM and
EF as shown in Table +. Despite the fact that theshovel load was + kg lower in EF than EM, shoveling-.+.

throw ability was signiﬁcantly lower in EF than EM.
Cardio-respiratory responses
Table , shows the mean value of cardio-respiratory responses to snow shoveling. At rest, systolicblood pressure were +.*῎/ vs +.*῎+* mmHg (ns) anddiastolic blood pressure were 2/῎/ vs 2/῎. mmHg(ns) respectively. Cardio-respiratory responses were
somewhat higher for EM than EF considering the factthat the heart rate (+/2῎/ vs +/*῎1 beats/min, ns),systolic blood pressure (+2-῎+* vs +12῎1 mmHg, ns),
diastolic blood pressure (3/῎. vs 2.῎2 mmHg, ns) andRPE (+..3῎*.1 vs +-.0῎*.., ns) were slightly higher in
EM than in EF. Heart rate during snow shovelingfrom the start to 1 minutes revealed similar trend
between males and females. Male subjects tend toexert higher pace at ﬁnal phase of exercise whilefemale subjects adjust their exertion somewhat lower.
These di#erences are considered to reﬂect on delay inrecovery period in male subjects
as shown in Fig. -.
῍Oxygen consumption (VO,) in terms of absolutevalue (+.13῎*.*1 vs +.,*῎*.*0 Lῌmin῍+, pῐ*.**+), relative value (,2.0῎+.0 vs ,-.*῎+.* mLῌkgῌmin῍+, pῐ*.*/) and metabolic equivalent (2.,῎*./ vs 0.0῎*.Mets, pῐ*.*/) were signiﬁcantly higher in EM than
MF.
-.,.

Morita et al.

45

Fig. -. Trendgraph of the heart rate at rest, during snow shoveling andrecovery in elderly males (N῎2) and females (N῎/). Value are mean῍SEE.

Table -. Comparisons in productivity variables of snow shoveling between
EM and EF.

ῌ+Shovel rate (scoopsῌmin )Shovel load (kg)Snow mass (kgῌminῌ+)

EM (n῎2)

EF (n῎/)p-value+*40῍*42++4*῍*40++.41῍14*+.4+῍*43.43῍*4+034,῍/4*

*4*+2
*4***
*4***

Values are means (S.E).

Productivity variables
Table - shows the mean value of the shovel rate,
shovel load and snow mass. There were large di#erences in shovel load (++.+῍*.0 vs ..3῍*.+kg, p῏*.**+)and snow mass (++..1῍0.2 vs 03.,῍..0 kgῌminῌ+, p῏*.**+) between EM and EF. On the other hand, theshovel rate was signiﬁcantly higher in EF than EM.
As illustrated in Figure ., remarkable di#erenceswere observed both in snow mass and oxygen consumption between EM and EF. Oxygen consumption
during snow shoveling increased proportionally withincrease in snow mass.
Table . presents correlation coe$cients between
the variables of physical resources as explanation
variables and snow mass as an objective variable.
Sit-and-reach to assess trunk ﬂexibility shows no relationship to snow mass. Variables in body dimensions,although showing signiﬁcant correlation, were relatively lower compared to the physical ﬁtness parameters. Considering the fact that the shovel load in theshoveling throw ability is heavier in males (/ kg) thanfemales (. kg), the shoveling throw ability is thought
to be a good predictor for snow shoveling performance.

Table .. Correlation coe$cients between variables ofphysical resources and snow mass in overall subjects (N῎+-).

-.-.

r
Height (cm)*4/,/Weight (kg)*4.33
Grip strength*4133
Sit-and-reachῌ*4,,1
Sit-ups*410+
Back strength*4113
Shoveling throw ability*42,῍VO, during exercise (Lῌminῌ+)*42-,
῍VO, during exercise (mLῌkgῌminῌ+)*40+0-minutes walk distance*40+2
Leg extensor power
*403+

..

p-value*4*-*4*.+
*4**/
*411,
*4**+
*4**2
*4***
*4***
*4*+*4*+,*4**0Discussion

The major ﬁndings of this study are: +) elderly
males performed signiﬁcantly higher shovel productivity expressed as lift-and-throw snow mass (kgῌminῌ+) than elderly females under slightly higher cardio-respiratory responses; ,) the lower value of snow
mass in elderly females is considered to be due to the46

Bulletin of Glaciological Research

῍Fig. .. Snow mass (kgῌminῌ+, x) and VO, (Lῌminῌ+, y) in elderly males and elderly
females during snow shoveling.

disadvantage
in smaller body size and lower physical῍ﬁtness; -) VO, increased proportionallywith snow
῍
mass, and .) di#erences in VO, (,.῎) in terms of
relative value (mLῌkgῌminῌ+) or metabolic equivalent (,.῎)
between males and females were enlarged
῍
when VO, was expressed as absolute value (.3῎) andreﬂected on the large di#erence in snow mass (00῎).
Cardio-respiratory responses to snow shoveling
The strenuous nature of snow shoveling are well
documented by previous studies (Suda et. al. +33*;
Sheldahl et al. +33,, +33-; Franklin et al. +33/; Smolander et al. +33/). In this study, mean values in oxygen
consumption during῍ snow shoveling expressed as an
absolute value in VO, (+.13῍*.*1 vs +.,*῍*.*0 Lῌ
minῌ+), relative value (,2.0῍+.0 vs ,-.*῍+.* mLῌ
minῌ+), metabolic equivalent (2.,῍*./ vs 0.0῍*.- Mets)
were signiﬁcantly higher in EM than those in EF. As
presented in Table /, exercise intensity in terms of
metabolic equivalent (2., Mets) of EM in this study
revealed lower than that during snow removal using asnow pusher by middle-aged males (3./ Mets) reported
by Smolander et al. (+33/) but higher than those during snow shoveling performed by middle aged males(Sheldahl et al., +33,; Franklin et al., +33/), patients ofcoronary artery disease (Sheldahl et al., +33-), middleaged females (Sheldahl et al., +33-) or elderly males(Suda et al., +33*; Sheldahl et al., +33-). This tendency
was also observed in EF in this study. Oxygen consumption in terms of metabolic equivalent in EF was..+.

higher than that during snow shoveling performed byfemale subjects reported by Sheldahl et al. (+33-).
At any rate, both in EM and EF, exercise intensity
in this study were classiﬁed as “vigorous activity,”deﬁned as greater than 0 Mets, in accordance with
ACSM (,***) guidelines. Heart rate during steadystate reached almost HRmax (31῎ in males and 3-῎ infemales) of the estimated value derived from new
formula (HRmax῏,*2ῌ(*.1῎age)) proposed by Tanaka
et al. (,**+). Considering that there exist large variation in maximum heart rate among older populationand that RPE were not extremely high, averaging +..3
(correspond to “hard “) in EM and +-.0 (in the midst of“somewhat hard” and “hard”) in EF, the snow shoveling demand highly on cardiovascular function as reported by Franklin et al. (+330).
Oxygen consumption during snow shoveling increased proportionally with increase in snow mass asshown in Figure -. These data are consistent with aprevious study on elderly males showing that oxygen
consumption correlate signiﬁcantly (r῏*.102, N῏+-, pῐ*.*+) (Suda et al., +33*) with snow mass. Therefore, it
is obvious that aerobic power may be one of thedeterminants of snow shoveling performance. Oxygen
consumption during shoveling exceeded 2 Mets in elderly males and exceeded 0 Mets in ῍elderly females.
These intensities correspond to 2*῎VO, max of average values for Japanese males and females in their 0*’s (Physical ﬁtness laboratory Tokyo Metropolitan
University, ,***). Therefore, snow shoveling requires

Morita et al.

high oxygen consumption and demands on cardiovascular function as pointed out from previous studies(Suda et al., +33*; Sheldahl et al., +33,, +33-; Smolander
et al., +33/; Franklin et al., +33/, +330), considering thefact that the duration of work last for occasionallyseveral hours after a heavy snowfall. Such strenuous
exercise is rare in daily physical activities for theelderly in developed countries.
Relationship between physical resources and shovel productivity
The present study, to our knowledge, is the ﬁrst
to provide the inter-relationship among physical resources, cardio-respiratory responses and shovelingperformance in snow shoveling in elderly men andwomen. Although the sample size was limited insmall, physical ﬁtness such as muscle strength, muscle
power and endurance correlated signiﬁcantly withsnow shoveling performance in terms of snow mass.
Suda et al. (,**/) pointed out that muscle strength andleg extensor power are essential determinants for elderly people living in snowy regions since muscle strength, represented by grip strength and back strengthand leg extensor power correlated signiﬁcantly withshoveling throw ability.
The higher correlation coe$cient between shoveling throw ability and snow mass shows why theshoveling throw ability test was developed to assess
the functional mobility for people in snowy regionswith special relation to snow shoveling and involves
various factors such as body size, muscle strength,
power and throwing skill of shovel load.
Figure . shows the existence of a di#erent patternin shoveling strategy between males and females. Female subjects tend to maintain a certain rate of scooping to compensate their disadvantage in lower shovel
load than male subjects. On the other hand, the current study suggests that there are other factors thatinﬂuence shoveling performance. The data included
the cases showing that subjects of higher strength,
power, endurance or shovel power did not attain highshovel performanceboth EM and EF.
῍
The absolute VO, (Lῌminῌ+) correlated highly(r῍
῍*.2-,) than with snow mass than the relative VO,(mLῌkgῌminῌ+) (r῍*.0+-). Among various daily physical activities, oxygen consumption of the locomotive type of exercises (weight-bearing) such as walking, running,
cycling, stair climbing, are expressed as
῍relativeV
O,, to cancel the e#ect of body weight divid῍῍
ing VO, by body weight) and usually relative VO, isconsidered to be the most important factor as “healthrelated ﬁtness” or “sport-related ﬁtness”. This tendency was also observed with young subjects (Morita
et al., in press).
Although the importance of relative VO, is well
documented, the present
investigation elucidated the῍importance of absolute VO, to attain higher shoveling
..,.

47

performance. This characteristic is explained by thedi#erence in the type of exercise, that is to say, in caseof snow shoveling, a large proportion of energy isallocated to external work to lift-and-throw shovel
load and the energy for locomotion is small. Thisﬁnding is necessary to remind people living in snowy
region of the disadvantage in snow shoveling for
older women who are smaller in body size and lower
in muscle strength and power. Nevertheless, in Japanese, many elderly people who are unﬁt or having
health problem are forced to engage in demanding
snow removal with no support from family or neighbors.
Required level of ﬁtness for the maintenance ofindependency in snowy regions
A positive signiﬁcant correlation (r῍*.10/, p῏*.*+) was found between the shovel load and the snow
mass. These results are consistent with previous ﬁndings (Suda et al., +33*). Although this strategy may
be advantageous to attain higher performance for
elderly people, may increase the risk of heart attack
induced by increase of systolic blood pressure triggered by Valsalva maneuver of isometric contractionand exposure to cold environment as pointed out by
Franklin et al. (+33/).
Shephard (+321) had proposed that an oxygen
uptake of +/ mLῌkgῌ+ῌminῌ+ (..- Mets) was the threshold for the activities of daily living. Paterson et al.
(+333) also reported that the minimum level of aerobic
power compatible with an independent life at age 2/
yr was approximately +2 mLῌkgῌ+ῌminῌ+ (/.+ Mets)
in men and +/ mLῌkgῌ+ῌminῌ+ (..- Mets) in women.
These values are assumed to require to perform acertain minutes of usual task such as level walking at
2* mῌminῌ+ (-./ Mets). However, it is obvious thatthese criterions do not satisfy the independency of theelderly people living in snowy regions who have nosupport for removing snow due to the fact that oxygen consumption of snow shoveling by women of /*ththe amount to /., Mets during snow shoveling as pointed out by Sheldahl (+33,) and that by women of 0*th
averaged 0.0 Mets in the present study. Even if unﬁt
women try to the adjust intensity to their physicalresources by lowering the shovel load and shovel rate,
this strategy requires prolonged work time under cold
temperature.
In this study, relationships between shovel powerand snow mass remain unclear since higher performance was not attained by heavier shovel load despite
the signiﬁcant correlation (r῍*.2.3, p῎*.*+) being observed by overall subjects, the highest performer was
not higher in shoveling throw ability both in EM and
EF. Further study is needed to elucidate which factor
in physical resources is important for higher performance in snow shoveling and to distinguish the characteristics.
..-.

48

Bulletin of Glaciological Research

Table /.

Intensities of snow removal reported by previous studies.

Authors

Type ofsnow removal

Subjects

Age ofsubjects

Franklin et al4 +33/
Franklin et al4 +33/
Suda et al4+33*
Sheldahl et al4 +33,
Sheldahl et al4 +33,
Smolander et al4+33/
Sheldahl et al4 +33Sheldahl et al4 +33Sheldahl et al4 +33Sheldahl et al4 +33-

Snow shoveling
Snow Blower
Snow shoveling
Snow shoveling
Snow shoveling
Snow pusher
Snow shoveling
Snow blower
Snow shoveling
Snow blower

+*M
+*M
+.M
+,M
+-M
3M
+,F
+,F
CAD2F
CAD2F

-,
-,
1.
.*
0+
.ῑ/*
ῑ/*
ῑ/*
ῑ/*

Heart rate
Intensity(beatsῌmin῍+)(Mets)
+1/
+,.
+,0
++0
++.
+.,
2/῍peakHR
12῍peakHR
2+῍peakHR
11῍peakHR

/41
,4.
/4/
14,
04.
34/
/4,
/4,
/4+
.40

CAD : Coronary artery disease.

Another limitation in the present study is that, toperform the experiment safely, subjects recruited forthe studies may be biased in favor of the more ﬁt
individuals than representatives of normal aging andexcluded subjects who have any cardio-vascular disorder or motor function since the snow shovelingdemand on cardio-vascular function and danger topersons with cardiac risk factors as pointed out by
Smolander et al. (+33/) or Franklin et al. (+33/).
As reported by Franklin et al. (+330), during snow
shoveling in +* sedentary men (mean age῎SD, -,..῎,.+ years), at a rate at which they removed snow athome, despite the fact that oxygen consumption was-3῍ lower (/.1 Mets) than these during maximal treadmill testing (3.- Mets; pῐ*.**-), the peak heart rate,
blood pressure, and perceived exertion increased highlevel, averaging +1/ beatsῌmin῍+, +32 mmHg, and +0.1
(very hard e#ort), respectively. These values werecomparable to or higher than the maximum values
achieved by the same subjects during maximal treadmill testing. Although perceived exertion in thisstudy were lower both in males and females thanthose in Franklin et al., the same tendency of increasein higher heart rate were observed in this study. Therefore, warning signs of over exertion may be deceptively camouﬂaged by the moderate aerobic requirement (Mets) or perceived exertion.

/.

Conclusion

The main ﬁndings obtained from the measurements of cardio-respiratory responses to +* minutes ofsnow shoveling and shoveling productivity in +- healthy elderly subjects (2 males and / females) were as
follows:
ῌ There was no signiﬁcant di#erence between EM
and EF in cardiovascular function. The heart rateduring a steady state of exercise reached almost
the same level as the estimated nearly maximum
value both in EM (+/2῎/ beatsῌmin῍+) and EF(+/*῎1 beatsῌmin῍+). Blood pressure immediately

after exercise was slightly higher in EM than in
EF both for systolic blood pressure (+2-῎+* vs.
+12῎1 mmHg, ns) and diastolic blood pressure (3/῎. vs. 2.῎2 mmHg, ns)
ῌ Oxygen consumption in terms of the relativevalue was ,.῍ higher in EM than MF (,2.0῎+.0
vs. ,-.*῎+.* mLῌkgῌmin῍+, pῐ*.*+). The di#erence was increased when oxygen consumption
was expressed as absolute VO, (+.13῎*.*1 vs. +.,*
῎*.*0 Lῌmin῍+, ῌ.3῍, pῐ*.**+). Oxygen consumption in terms of absolute VO, correlates withsnow mass higher (r῏*.2-,, pῐ*.**+) than relative
VO, (r῏*.0+-, pῐ*.*/). These relations suggestthat performance in snow shoveling is a#ected
not only by aerobic power, but also by body size.
ῌ There was a large di#erence in snow mass, expressed as the weight of lift-and-throw snow per
minute between EM and EF (++/῎+2 vs. 03῎3kgῌmin῍+, pῐ*.**+); the di#erence was due toshovel load (++..῎,.* vs. ..3῎*.. kg/scoop, pῐ*.**+) not shovel rate (+*.-῎,.- vs. +..*῎+.3 scoopsῌmin῍+, pῐ*.*/). These characteristics explain how snow shoveling is demanding work forthe elderly. Elderly female are disadvantage forshovel performance due to smaller body size,
lower muscle strength, muscle power and aerobic
power.

Acknowledgment
We would like to thank Professor Eiji Akitaya forthe help in measuring the density of snow. This study
was supported in part by a Grant in Aid for ScientiﬁcResearch from the Japanese Ministry of Education,
Science, Culture, Sport and Technology (,**+ῌ,**-).

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