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Abstract

Introduction

Annually, approximately 250,000 people climb Mount Fuji in Japan. Nonetheless, only few studies have examined the prevalence of falls and related factors on Mount Fuji.

Methods

We conducted a questionnaire survey of 1061 participants (703 men and 358 women) who had climbed Mount Fuji. The following information was collected: age, height, body weight, luggage weight, experience on Mount Fuji, experience on other mountains, presence or absence of a tour guide, single-day climber or overnight-stay lodger, information on the downhill trail (volcanic gravel, long distance, and the risk of falls), presence or absence of trekking poles, shoe type, shoe sole condition, and fatigue feeling.

Results

The fall rate in women (174/358; 49%) was greater than that in men (246/703; 35%). A prediction model using multiple logistic regression (no fall, 0; fall, 1) indicated that the following factors decreased the risk of falls: male sex, younger age, previous experience on Mount Fuji, having information about long-distance downhill trails, wearing hiking shoes or mountaineering boots rather than other types of shoes (eg, running shoes, sneakers) or worn-out shoes, and not feeling fatigued. Additionally, the following factors may decrease the risk of falls in women only: experience hiking on any other mountains, not being part of a guided tour, and using trekking poles.

Conclusions

Women had a higher risk of falls on Mount Fuji than men. Specifically, having less experience on any other mountains, being part of a guided tour, and nonuse of trekking poles may relate to higher risks of falls in women. These results suggest that different precautionary measures for men and women are useful.

Keywords

experience on mountains guide tour multiple logistic regression sex difference trekking pole use

Introduction

It has been estimated that approximately 100 million tourists visit high altitudes worldwide (>2000 m).¹ In Japan, mountain climbing has become popular over the last decade. Additionally, the number of fall-related accidents has progressively increased. For example, there was a 1.5-fold increase in the annual number of accidents between 2006 and 2014 in the Austrian Alps.¹ According to a report by the Japan Mountaineering and Sports Climbing Association, approximately 49% of mountain climbing-related accidents are caused by falls.²

We recently investigated the prevalence of falls on Mount Fuji in Japan and found that approximately 30% of climbers fell.³ A multiple logistic regression model was used to derive risk factors such as female sex, having no prior climbing experience on Mount Fuji, and not staying at a lodge. A methodologic shortcoming was shown to be associated in a previous study,³ which warrants further investigation. Several factors, including but not limited to obesity,⁴ footwear,⁵ unexpected road surfaces,⁶ load carriage,⁷ nonuse of trekking poles,⁸ and lack of information on the risk of falls,⁹ have been shown to increase the risk of falls or slips potentially; however, the previous study did not evaluate these potential factors.³ It can be considered that information about the risk of falls during mountain climbing may depend on the mountain per se (knowledge of descending roads such as road surface, standard descending time, and decline level). Therefore, further studies about the prevalence of falls and related factors on Mount Fuji, including other potential factors,⁴^-9 are warranted.

Additionally, among risk factors in the previous study,³ female sex needed further consideration. A previous study demonstrated that fall-related accidents during descent were more common among women, although the study was conducted in the Austrian Alps.¹ Another study reported that women had a greater difference in overall change in angular momentum during descent than men, suggesting a greater risk of falls in women.¹⁰ Mount Fuji (altitude, 3776 m) is the highest mountain in Japan and is a known United Nations Educational, Scientific and Cultural Organization (UNESCO) World Cultural Heritage Site. Approximately 250,000 people climb Mount Fuji annually. In this regard, the prevention of falls is important for safe and comfortable climbing because falls can potentially cause more or less serious bruises, sprains, and fractures. Moreover, it is possible that people with injuries cannot move by themselves.

Given this background, we conducted a questionnaire survey, further expanding from a previous study³ on Mount Fuji. Specifically, we used additional questions and hypothesized that climbers with obesity, those with heavier baggage, those with insufficient climbing gear (ie, shoes and trekking poles), and those with less information about the descending road on Mount Fuji were likely to have more fall experiences. Second, we investigated the sex differences in fall incidences among potential candidates and hypothesized that women would have a higher risk of falls than men. The risk factors would still be different between the sexes.

Methods

Survey Site

We selected the same points for the questionnaire survey study based on our previous study. The questionnaire survey site was established at the Yoshida trailhead sign (altitude, 2280 m) and not the Fuji-Subaru Line parking lot (altitude, 2305 m), which is approximately a 20-min walk from the survey site. The survey site was chosen because we considered that we would not be able to distinguish between tourists and climbers accurately because numerous tourists (not climbers) and climbers visit the parking lot. The altitude of the survey site was 2269 m, and that of the summit of Mount Fuji was 3776 m. According to the guideline of the Ministry of the Environment Government of Japan, the general required time from the survey site to the summit of Mount Fuji (ascending time) was 350 minutes for approximately 5.0 km, with a mean gradient of 30%, and that from the summit of Mount Fuji to the survey site (descending time) was 215 minutes for approximately 6.4 km, with a mean gradient of −24%.

Participants and Sample Size

This study consisted of only a questionnaire survey study, and it was approved by the ethics committee of the Mount Fuji Research Institute in Japan in line with the Declaration of Helsinki (ECAE-01-2018). After providing a detailed explanation of the study, informed consent was obtained from each participant. We surveyed descending Japanese (Table 1) climbers who reached the survey site of Mount Fuji on August 3, 4, and 21, 2019; July 18, 24, and 25, 2021; and August 1, 8, and 9, 2021. Closure of the climbing road owing to coronavirus disease 2019 led to lack of data in 2020. Participants were surveyed between 0800 and 1200. We confirmed the following criteria for all participants: descended on the Yoshida trail road, first response to the survey, and had sufficient time (approximately 15 min) to complete the questionnaire carefully. Individual participants who volunteered to respond were included in the survey to avoid responses made under pressure or after consultation with friends. Only under these conditions, the questionnaire survey sheet was handed over.

Table 1

Questionnaire survey sheet used in the present study

Please respond to the following questions with respect to falls and their situations
Did you fall	1. Yes (ground contact with any portions of the body) → Respond to the below questions 2. No → Respond to the next section
Number of falls	Fall down about____times in total (a. Ascent:____times b. Descent____times)
Motion of falls (multiple answers possible)	1. Stagger 2. Stumble 3. Slip 4. Caught pole 5. Other ( )
Injury status when falling	1. None 2. Knee pain 3. Ankle sprain 4. Scratch 5. Other
Please respond to the following questions (parameters 1–15 in the main text)
1) Age	___years old
2) Sex	1. Male 2. Female
3) Height, cm	__cm
4) Body weight, kg	__kg
5) Backpack weight, kg	Ask the staff to weigh your current luggage and fill it below __kg
6) Prior climbing experience on Mount Fuji	1. First time 2. More than once
7) Climbing experience on other mountains, years	1. <2 2. >2
8) Tour guide	1. With tour guide 2. Without tour guide
9) Trailhead (fifth station) at the starting point	1. Yoshida (Fuji-Subaru line) 2. Subashiri 3. Gotenba 4. Fujinomiya 5. Other (__)
10) Staying	1. Overnight-stay lodger 2. Single-day climber
11) Summit a success	1. Reached 2. Failed
12) Information about descending the road before climbing	a. Know the downhill trail is volcanic gravel? 1. Known 2. Unknown b. Know the downhill trail distance is long? 1. Known 2. Unknown c. Know that you have to be careful while climbing Mount Fuji to prevent fall? 1. Known 2. Unknown
13) Trekking pole use	1. Yes (with) 2. No (without)
14) Shoe type	1. Hiking shoes or mountaineering boots 2. Other types of shoes (eg, running shoes, sneakers)
15) Current condition of your shoe sole	1. Almost not worn out 2. Moderately worn out 3. Quite worn out

Please tell me about your current conditions. Please mark only 1 appropriate answer with a circle (parameter 16 in the main text)
	Disagree completely	Agree scarcely	Agree slightly	Agree considerably	Agree strongly
1 I feel heavy in the head	1	2	3	4	5
2 I feel nervous	1	2	3	4	5
3 I feel that my eyes are dry	1	2	3	4	5
4 I feel ill	1	2	3	4	5
5 I feel restless	1	2	3	4	5
6 I feel a headache	1	2	3	4	5
7 I feel pain in the eyes	1	2	3	4	5
8 I feel stiff in the neck and shoulders	1	2	3	4	5
9 I feel the brain hot or muddled	1	2	3	4	5
10 I feel like yawning	1	2	3	4	5
11 I feel pain in the hands or fingers	1	2	3	4	5
12 I feel dizzy	1	2	3	4	5
13 I feel drowsy	1	2	3	4	5
14 I feel a lack of desire to do something	1	2	3	4	5
15 I feel anxious	1	2	3	4	5
16 I feel that my eyes are blurry	1	2	3	4	5
17 I feel tired in the whole body	1	2	3	4	5
18 I feel depressed	1	2	3	4	5
19 I feel dullness in the arms	1	2	3	4	5
20 I feel difficulty in thinking	1	2	3	4	5
21 I feel the desire to lie down	1	2	3	4	5
22 I feel eyestrain	1	2	3	4	5
23 I feel lower-back pain	1	2	3	4	5
24 I feel that my eyes are blinking	1	2	3	4	5
25 I feel tired in the legs	1	2	3	4	5

The questions are over. We appreciate your cooperation.

The original questionnaire survey sheet was written in Japanese as the participants were all Japanese populations. This sheet was translated into English for readers.

We determined the sample size based on a prior test using R (version 4.1.2.), assuming a fall rate of 25% and 39% in men and women, respectively.³ We estimated a sufficient sample size of 322 men and 197 women, with α error of 0.05 and power (1−β probability) of 0.90.

Questionnaire

Table 1 lists the questionnaire parameters used in this study based on our previous study.³ It should be noted that we conducted this study on only Japanese participants, and, hence, Table 1 was translated into English by a professional English-editing service. The questionnaire asked if they had fallen, “fallen” being defined as “ground contact with any portion of the body other than the feet (yes or no).” The items assessed were as follows: number of falls, motion of falls (stagger, stumbling, slip, trekking pole, and others), and injury status when they fell (none, knee pain, sprained ankle, scratch, and others).

The survey also evaluated the following 16 parameters: 1) age, 2) sex, 3) height, 4) body weight, 5) backpack weight, 6) climbing experience on Mount Fuji, 7) climbing experience on any other mountains, 8) presence or absence of a tour guide, 9) trailhead at the starting point, 10) single-day climber or overnight lodger, 11) summit success, 12) information about the downhill trail, 13) use of trekking poles, 14) shoe type, 15) current shoe sole condition, and 16) a 25-item questionnaire for the feeling of fatigue. Each item relating to fatigue was scored from 1 to 5 (from disagree completely to agree strongly; Table 1).^3,11 The body mass index (BMI) was calculated by dividing the body weight (kg) by squared height (m).

Weather Information

The ambient temperature and relative humidity at the top of Mount Fuji on the survey days were obtained from Japan Meteorological Agency data.

Statistical Analyses

All statistical analyses were performed using R, version 4.1.2.¹² Multiple logistic regression analysis was performed to identify important factors affecting the incidence of falls in all participants. The dependent variables in this analysis were fall (scored as 1) and no fall (scored as 0). We conducted multiple logistic regression analysis with 29 independent variables, including 15 independent variables (Table 2) and 14 sex interaction terms (ie, sex×each variable). Then, we performed model selection by backward stepwise elimination using the Akaike information criterion (AIC) to find a prediction model containing parameters that best explain data, including interaction effects of sexes. During the process, the least important variables were deleted 1 by 1 to get lower AIC values, and this process was performed until the AIC values reached values higher than those obtained using a prior model.¹³ Of them, we adopted the model with the lowest AIC values. Because AIC can take the place of the P value, providing its predictive accuracy of the model,¹⁴ we determined that the model with the lowest AIC value was a prediction model in the present study.

Table 2

Dependent and independent variables for multiple logistic regression analysis

Classfication of variables	Survey items	Dummy variables
		0	1	2
Dependent variables	Fall status	No fall	Fall
Independent variables (category)	Sex	Male	Female	-
	Experience on Mount Fuji	First time	More than twice	-
	Experience on other mountains	<2 y	>2 y	-
	Guided tour	Without	With	-
	Stay	Not stayed	Stayed	-
	Information for downhill trail
	Volcanic gravel	Unknown	Known	-
	Long distance	Unknown	Known	-
	Risk of fall	Unknown	Known	-
	Use of poles	Without	With	-
	Shoe type	Other shoes	Hiking shoes or mountaineering boots	-
Independent variables (order)	Shoe sole condition	Not worn out	Moderately worn out	Quite worn out
Independent variables (continuous)	Age, y
	Body mass index, kg/m²
	Relative backpack weight, %
	Fatigue feeling

If a sex interaction was detected, estimates for the effect of risk factor were made for each sex separately using nested effects in the multivariable logistic regression model.

Results

The mean±SD values during the 9 survey days at the summit of Mount Fuji were as follows: barometric pressure, 648±5 hPa; ambient temperature, 7.5±1.2°C; relative humidity, 71±27%; and sunshine time, 8±6 h. To avoid any bias of the effects of weather on the risk of falls, we did not conduct the survey study in bad weather conditions such as wind, rain, or typhoon. Considering possible wet and slippery descending roads, we also avoided conducting the survey study on the day after rainy and typhoon days.

Throughout the survey days, we asked 2192 participants to respond to our survey. Of them, 775 participants refused to respond (rejection rate, 35%). Thus, a total of 1417 Japanese participants responded to the survey, and we excluded 199 survey sheets based on the following criteria: 1) age <15 y because we considered that it might be difficult for participants aged <15 y to respond (n=3), 2) the starting point was not the Yoshida trailhead (Fuji-Subaru Line) because different ascending roads may affect the falling status among individuals (n=64), 3) not reaching the summit because the descending road (eg, distance) would vary when the starting point is different (n=112), and 4) the shoe sole condition was breakage (n=24). These 4 criteria (n=203) are considered to be outside of the scope of the present study. Of note, this number, summing of points 1) to 4), included duplicate answers; so, the actual deleted number was 199, as mentioned above (ie, 1417−199=1218). Furthermore, we excluded 157 incomplete responses. As a result, we obtained 1061 valid responses (703 men and 358 women) from 1218 survey sheets (effective response rate, 87.1%; ie, [1061/1218]×100). Among men and women, 246 (fall rate, 35%) and 174 (fall rate, 49%) participants, respectively, had falls. The main motion of falls was slip (62% for men and 63% for women).

The attributes of men and women are summarized in Table 3. The mean values and SD in participants who had falls or no fall for each of the continuous variables were calculated, and the number of participants who had falls or no fall was calculated for the remaining categorical variables.

Table 3

Characteristics of the surveyed independent variables in men and women^a

Independent variables	Men		Women
	No fall	Fall	No fall	Fall
Age, y	36±13	37±14	37±14	36±14
BMI, kg/m²	22.8±3.0	22.9±2.9	20.8±2.4	20.8±2.5
Relative backpack weight, %	9.1±3.2	8.8±3.2	10.5±2.9	10.2±3.8
Experience on Mount Fuji
First time, n (%)	284 (62)	168 (68)	116 (63)	136 (78)
More than once, n (%)	173 (38)	78 (32)	68(37)	38(22)
Experience on other mountains
<2 y, n (%)	283 (62)	162 (66)	110 (60)	125 (72)
>2 y, n (%)	174 (38)	84 (34)	74 (40)	49 (28)
Guided tour
Without tour guide, n (%)	350 (77)	195 (79)	125 (68)	101 (58)
With tour guide, n (%)	107 (23)	51 (21)	59 (32)	73 (42)
Stay
Not stayed, n (%)	66 (14)	38 (15)	15 (8)	13 (7)
Stayed, n (%)	391 (86)	208 (85)	169 (92)	161 (93)
Information about downhill trail
Volcanic gravel
Unknown, n (%)	174 (38)	110 (45)	58 (32)	83 (48)
Known, n (%)	283 (62)	136 (55)	126 (68)	91 (52)
Long distance
Unknown, n (%)	195 (43)	136 (55)	72 (39)	97 (56)
Known, n (%)	262 (57)	110 (45)	112 (61)	77 (44)
Risk of fall
Unknown, n (%)	134 (29)	85 (35)	50 (27)	67 (39)
Known, n (%)	323 (71)	161 (65)	134 (73)	107 (61)
Use of poles
No, n (%)	178 (39)	98 (40)	33 (18)	54 (31)
Yes, n (%)	279 (61)	148 (60)	151 (82)	120 (69)
Shoe type
Hiking shoes or mountaineering boots, n (%)	407 (89)	194 (79)	176 (96)	160 (92)
Other shoes, n (%)	50 (11)	52 (21)	8 (4)	14 (8)
Shoe sole condition
Not worn out, n (%)	270 (59)	117 (48)	130 (71)	100 (57)
Moderately worn out, n (%)	168 (37)	113 (46)	54 (29)	66 (38)
Quite worn out, n (%)	19 (4)	16 (6)	0 (0)	8 (5)
Fatigue feeling	48±17	54±16	49±17	54±17

BMI, body mass index.

For the categorical variables, the number of participants belonging to different categories and their proportions (in parentheses) are shown. When analyzing, set the top category to 0 and the bottom to 1. For continuous variables, the values are represented as the means±SDs.

In the prediction model, the risk of falls was explained by the following 13 variables: sex, age, experience on Mount Fuji, experience on any other mountains, guided tour, information about long-distance trails, use of trekking poles, shoe type, shoe sole condition, fatigue feeling, “sex×experience on any other mountains,” “sex×guided tour,” and “sex×trekking pole use” (Table 4). After further analysis of these 3 derived variables with interaction effects of sexes, women who used poles experienced decreased falls or those with experience on any other mountains (>2 y) had a lower risk of falls. In contrast, women with guided tours experienced increased falls. In men, these variables did not affect the risk of falls (Table 4).

Table 4

Summarized results of multiple logistic regression analysis using backward stepwise method^a

Variables	OR	95% CI		P values
Variables	OR	Lower	Upper	P values
Sex	1.402	1.223	1.609	<0.001
Age	1.280	1.102	1.489	0.001
Experience on Mount Fuji	0.866	0.741	1.010	0.067
Experience on any other mountains	0.947	0.820	1.093	0.459
Guided tour	0.995	0.865	1.141	0.940
Information about long distance	0.816	0.702	0.948	0.008
Use of trekking poles	0.823	0.713	0.949	0.007
Shoe type	0.812	0.708	0.931	0.003
Shoe sole condition	1.252	1.096	1.431	0.001
Fatigue feeling	1.327	1.157	1.524	<0.001
Sex×experience on any other mountains	0.908	0.794	1.037	0.154
Men×>2 y	1.015	0.869	1.185	0.847
Women×>2 y	0.882	0.755	1.030	0.115
Sex×guided tour	1.151	1.012	1.312	0.033
Men×guided tour	0.917	0.795	1.055	0.232
Women×guided tour	1.151	0.984	1.347	0.079
Sex×pole use	0.837	0.726	0.963	0.014
Men×pole use	0.936	0.788	1.111	0.446
Women×pole use	0.665	0.523	0.840	<0.001

OR, odds ratio.

Note that bold columns in each interaction effects of sexes indicate the estimated effect within each sex group in the multivariable model. These analyses used standardized data.

The numerical values of 95% CI indicate those of OR.

Discussion

This study’s major findings are as follows: 1) the prevalence of falls in women (49%) was greater than that in men (35%); 2) women with experience of >2 y on any other mountains or those using poles may experience decreased falls; however, those with guided tours may experience increased falls; and 3) these 3 factors were not independent risk factors for falls in men. These results suggest that different dissemination patterns are required for men and women to prevent falls on Mount Fuji.

Differences in Fall Risk-Related Factors Between Men and Women

In support of our second hypothesis, women had a higher risk of falls than men, which was also in agreement with the findings from our previous study.³ This finding suggests that specific factors exist to account for the higher risk of falls on Mount Fuji in women. It is natural that mountain climbing involves both uphill and downhill roads, posing challenges to those who are novice or have less experience in mountain trekking.⁸ Previous studies have demonstrated that prior experience in downhill walking (preconditioning) could attenuate downhill walking-induced muscle damage at a later date,^15,16 and the effects could last at least for 4 wk.¹⁵ These results suggest that many experiences in trekking on any other mountain affect the risk of falls. Although experience of >2 y on any other mountain may be related to the risk of falls in women, this factor did not strongly affect the risk of falls in men (Table 4). Therefore, future studies evaluating more detailed experiences of mountain trekking to elucidate a causal relationship between experience on any other mountains and the risk of falls between the sexes are needed.

In the present study, women climbers with a tour guide and without trekking poles were more likely to have a higher risk of falling. Although highly speculative, there is a possibility that novice female climbers tend to select a guided tour. This speculation might be supported by the results that less experience on any other mountains influenced the risk of falls in women (Table 4). The prediction model in the present study extracted the interaction effects of “sex×trekking pole use.” These results indicate that the use of trekking poles is protective for women and has no effect on men (odds ratio, 0.936 for men and 0.665 for women). It is considered that tour guides would give a lecture on how to use trekking poles (eg, for their body stabilization) to reduce the risk of falls. Indeed, a previous study demonstrated that the use of trekking poles reduced muscle damage during descent⁸ and suggested that sufficient knowledge of the use of trekking poles could reduce the risk of falls.⁸ Moreover, the literature has shown that the use of trekking poles potentially decreased lower-extremity muscle activity, suggesting decreases in muscle fatigue.¹⁷ Of note, we did not differentiate the numbers of poles used, eg, 1 vs 2 trekking poles. The present study could not clarify the effects of these different numbers of trekking poles on falls. However, a dynamic balance improved with either 1 or 2 poles compared with the no-pole condition, with no differences found between 1 and 2 poles.¹⁸ Thus, the use of trekking poles, irrespective of the number of poles, may reduce the risk of falls. Nonetheless, the differential sex effects of the use of poles on the risk of falls remain unknown, and, hence, future studies are warranted.

Common Risk Factors for Men and Women

A recent study demonstrated that the number of victims of fall-related accidents during mountain hiking progressively increases with advancing age.¹⁹ The ratio values among all victims (n=405) aged <40 y were <20%. In contrast, the ratio values in those aged >61 y were >40%.¹⁹ Although the precise reasons are still unclear, our results were supported by these previous findings.¹⁹ In agreement with our previous study,³ less experience on Mount Fuji was related to a higher risk of falls, regardless of sex (Table 4). These results suggest that the risk of falls on Mount Fuji is independent of experience on any other mountains, probably because of a rare descending trail such that the road is covered by scoria, is steep, and is longer.^3,20

In partial support of our first hypothesis, less information about long-distance downhill trails was derived as a fall-related risk factor. It was suggested that unknown longer distances during a leg cycling time trial decreased power output, suggesting enhanced muscle fatigue.²¹ Additionally, localized muscle fatigue has been reported as a potential risk factor for slip-induced falls.²² Therefore, information about long-distance trails before descending may reduce the risk of falls.

Shoe sole tread groove depth²³ and material hardness²⁴ affect the coefficient of friction, which may be associated with the risk of slips and falls. Thus, it is possible that participants who fell chose running shoes (sneakers) rather than hiking shoes (mountaineering boots) and had a higher risk of fall. Additionally, shoe-ankle orthosis, which can control the position and motion of the ankle, improves balance in older participants, potentially reducing the risk of falls.^25,26 Although we did not measure the tread groove depth and material hardness, it can be generally considered that compared with running shoes (sneakers), hiking shoes (mountaineering boots) have a deeper groove, with harder material, and cover higher parts (eg, nearly the soleus muscle), which is partially similar to shoe-ankle orthosis. Worn-out shoe sole was identified as a risk factor for falls in men and women. Previous studies have demonstrated that naturally or artificially worn-out shoes reduce the coefficient of friction between the shoe and floor.^27,28 Lower coefficient of friction values have been associated with a higher risk of slips, leading to an increased risk of falls.²⁹^-32 Moreover, a recent study found that larger sizes of the worn-out region are associated with an increased occurrence of slips.³³ Our results may be accounted for by these findings, and they indicate similar effects of worn-out shoe soles on the increased risk of falls, regardless of sex.

Mental fatigue is related to the risk of slips and falls,³⁴ suggesting a potential relationship between an individual’s mental condition and an increased risk of falling. Because we recently reported that a subset of subjective feelings using the same questionnaire that was used in this study was derived to estimate the increases in the risk of falls on the same descending road (Yoshida trail) of Mount Fuji,³ we sought to confirm these effects on the risk of falls on Mount Fuji. Although the subjective fatigue feeling assessment tool that was used in the present study can evaluate the feeling of work-induced fatigue over time,¹¹ whether this assessment can be applied to the evaluation of the feeling of descending-induced fatigue remains uncertain. Additionally, the survey was conducted after the climb; therefore, there may have been a time difference between the fall and the feeling of fatigue. Given these, we must acknowledge that it may be difficult to clarify the causal relationship between the feeling of fatigue and increased risk of falls. Future studies are required to confirm this hypothesis.

Other Risk Factors For Falls in the Rejected Hypothesis

Contrary to our hypothesis, we found no effect of the degree of obesity or relative backpack weight on the risk of falls on Mount Fuji. Previous studies have reported that obesity is associated with a greater rate of slipping and falling,^4,35 which was not in agreement with our results. However, a previous study reported that individuals with a BMI of ≥30 kg/m² were 3 times more likely to experience falls than those with a BMI of <25 kg/m².³⁵ Yet, these BMI values in the previous study³⁵ are quite greater than those in people who experienced falls in the present study (mean BMI, 22.9 kg/m² for men and 20.8 kg/m² for women; Table 3). In addition, it is unlikely that populations without obesity in the present study may not have had an experience of the risk of falls.

Similarly, relative backpack weight (calculated as backpack weight per body weight×100 %) was not a risk factor for falls in either men or women. Loaded walking alters the gait pattern, and carrying unstable loads reduces dynamic stability, leading to an increased risk of falls.³⁶ A previous study also demonstrated that carrying a backpack with approximately 10% of body weight did not alter energy cost during walking in association with muscle fatigue.³⁷ These results make it difficult to obtain a consensus on the effects of backpack weight on the risk of falls. The present results showed that the numerical ranges of relative backpack weight between the sexes and between participants with falls and those without falls might be small (approximately 9–11% on average, Table 3). Based on previous findings³⁷ and the present results, the participants may have selected an appropriate backpack weight, irrespective of sex and fall or no fall.

Methodologic Considerations

The present study had several limitations. First, the primary data were obtained from the descending population between 0800 and 1200; therefore, we might have missed some of the climbers, especially those who descended earlier (dropout climbers or rapid-descent climbers) or later (climbers with severe fatigue and many falls) or people rescued by professional rescue teams. Similarly, because we could not count the number of participants who passed without being called by our staff because of the appearance of being in a hurry, we must acknowledge that these unknown responses may have affected our results. Moreover, we used the data of participants with only complete responses, that is, excluding incomplete responses. Although this number was 157 of 1218 (valid response rate, 87.1%), this valid response rate was apparently higher than that in our recent study (valid response rate, 69%).³ Second, we evaluated the degree of worn-out shoe soles as only 3 levels (almost not, moderately, and quite worn out), 1 of the main risk factors for falls in both men and women. However, a recent study demonstrated that a 1-mm increase in the length of the worn-out region of shoes might be associated with a 10% increase in the risk of slips.³³ Therefore, future studies that evaluate the quantitative aspects of wear level using a battery test, which has been assessed in a previous study,³⁸ may be required. Finally, the Yoshida trail was the only survey site, and our results were obtained from selected Japanese participants who climbed Mount Fuji; therefore, future studies of other routes and foreigners who visit Mount Fuji are necessary.

Conclusions

We found that women had a higher risk of falls on Mount Fuji than men. However, the predicted risk factors for falls differed between men and women. Less experience on any other mountains, guided tours, and nonuse of trekking poles were derived as risk factors for falls in women. These results suggest that different precautionary information may be useful for men and women.

Footnotes

Acknowledgments

The authors thank all participants for their time and effort.

Author Contributions: study concept and design (TU, MH); collection of data (TU, SM, MW, CT, MH); analyzing the data (TU, SM, MW, CT); interpretation of the results (TU, SM, MH); drafting of the first manuscript (TU, MH); revising the manuscript (SM, MW, CT); approval of the final manuscript (TU, SM, MW, CT, MH).

Financial/Material Support: This study was supported by a grant from the Japan Society for the Promotion of Science (KAKENHI, no. 20K12450 to TU).

Disclosures: None.

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Different Influencing Factors for Risk of Falls Between Men and Women while Descending from Mount Fuji

Abstract

Introduction

Methods

Results

Conclusions

Keywords

Introduction

Methods

Survey Site

Participants and Sample Size

Questionnaire

Weather Information

Statistical Analyses

Results

Discussion

Differences in Fall Risk-Related Factors Between Men and Women

Common Risk Factors for Men and Women

Other Risk Factors For Falls in the Rejected Hypothesis

Methodologic Considerations

Conclusions

Footnotes

Acknowledgments

References