Elsevier

Safety Science

Volume 43, Issue 7, August 2005, Pages 455-468
Safety Science

Slip and fall risk among firefighters in relation to balance, muscular capacities and age

https://doi.org/10.1016/j.ssci.2005.08.009Get rights and content

Abstract

Influencing the safety of firefighters’ work environment is almost impossible. Therefore, good individual physical capacities and adequate protective equipment are important in preventing accidents due to slips and falls. This study investigated slip and fall risk in walking experiments with firefighters wearing fire-protective equipment and determined the associations of balance, muscular capacities and age with the risk of slipping. Professional male firefighters aged 33–38 and 43–56 years (n = 14 and n = 15, respectively) participated in four slipping trials under different conditions on a straight path of 8 meters. Slip distances were measured in each trial. Postural balance and dynamic stability were tested on a force platform, and functional balance was measured during walking on a wooden plank. Muscular capacity of the legs and trunk were also measured. The average slip distances with glycerol were 9.7 ± 9.1 cm (100 steps/min) and 15.6 ± 18.2 cm (120 steps/min) in the 33-to-38-year age group and correspondingly 10.8 ± 15.3 cm and 18.0 ± 18.6 cm in the 43–56-year age group. Though the older firefighters tended to have longer and more serious slips than the younger ones, the differences in slip distances were not statistically significant. Half of the firefighters, regardless of their age, experienced critical, over 5-cm long, foot slides, considered to increase the risk of an unavoidable fall. These firefighters performed significantly poorer in the dynamic stability test as well, whereas associations with muscular capacity and risk of slipping were not significant. The results suggest that the ability to exploit visual feedback efficiently in balance control may be associated with smaller risk of slipping. This kind of test may be useful in evaluations of balance ability. The findings also support the importance of adding exercises which enhance balance ability to the exercise protocols of firefighters.

Introduction

In firefighting and rescue operations work conditions are unpredictable and rapidly changing. Surfaces can be slippery and passages narrow and smoky or totally dark. Firefighters work frequently on roofs and with ladders, and they smoke-dive (i.e., extinguish a fire and rescue victims in environment where is smoke and combustion gases), which also requires good balance and muscular capacities (Lusa et al., 1994). Besides of smoke-diving, also the other work tasks of firefighters often necessitate the use of fire-protective equipment, including fire-protective clothing and a self-contained breathing apparatus (SCBA). The SCBA increases strain on the postural control system by increasing postural sway, especially, when postural muscles are fatigued (Kincl et al., 2002). Furthermore, a large amount, about 30%, of work-related accidents among professional firefighters in Finland are due to slips or falls at the same level (Statistics Finland, 1996–2001). The proportion of slips and falls at the same level is lower (23%) among the working population in Finland (Statistics Finland, 2002). Compared with younger workers, workers over 45 years of age were reported to have a greater proportion of slip-, trip- and fall-related injuries (Kemmlert and Lundholm, 2001, Statistics Finland, 2002).

The heel contact phase in early stance and the push-off phase during late stance are considered the most critical phases in locomotion when a slip and fall may occur (Perkins, 1978, Redfern et al., 2001, Strandberg and Lanshammar, 1981). For measuring forward slipping after the heel contact, slip distances during walking are used as indicators of slipping and falling hazards or as a discriminating factor between a slip recovery and likely falling (Brady et al., 2000, Grönqvist et al., 1993, Strandberg and Lanshammar, 1981). Longer slip distances are associated with an increased risk of falling (Brady et al., 2000, Grönqvist et al., 1993, Strandberg and Lanshammar, 1981). The nature of slipping and falling events is complex. Therefore, different objective, subjective and combined approaches are needed and used for studying individual risks of slips and falls in a laboratory (Brady et al., 2000, Grönqvist et al., 1993, Grönqvist et al., 2001a, Grönqvist et al., 2001b, Hirvonen et al., 1994, Strandberg and Lanshammar, 1981, You et al., 2001). During the slipping event, however, the variable that, according to current knowledge, best describes the probable outcome of a foot slide is the slip distance (Brady et al., 2000). The critical slip distance between an avoidable and unavoidable fall is reported to be in the range 5–22 cm (Brady et al., 2000, Grönqvist et al., 1993, Grönqvist et al., 1999, Strandberg and Lanshammar, 1981). A slip distance less than a few centimeteres may not be perceived by a person as a slippery condition, while a slip distance over 5 cm may cause falling accidents (Grönqvist, 1995).

The risk exposure to slipping and falling depends primarily on poor friction between footwear and underfoot surfaces (Grönqvist et al., 2001b, Hanson et al., 1999). The friction demand, in terms of the peak required friction coefficient, has been reported to vary between 0.17 and 0.22 for normal walking on level surfaces (Redfern et al., 2001). The magnitude of a given risk exposure depends on several extrinsic and intrinsic factors, for example, lighting, an individual’s perception and cognition of the hazards and the ability to regain balance (Grönqvist et al., 2001b). Lockhart et al. (2000) showed that older people experience as many slips as middle-aged and younger people, but their horizontal heel velocities at heel contact are higher and the slip distances longer, resulting in a higher frequency of falls. The ability to recover successfully from a slip may be affected by a degradation of lower-legs muscle strength, sensory function and balance (Lockhart et al., 2000). In epidemiological studies, impaired balance and muscle strength are significant risk factors for falling among older people (Lord and Clark, 1996, Stalenhoef et al., 2002). Although the importance of balance, muscular abilities and age in the risk of slipping and falling is recognized, still little is known about how these factors are associated with biomechanical parameters of slip and fall risk. The aim of this study was to investigate the slip and fall risk in walking experiments with firefighters who wore fire-protective equipment and to determine the associations of balance, muscular capacities and age with the risk of slipping.

Section snippets

Subjects

The subjects were a subgroup (n = 29) of 69 male firefighters who participated in a 3-year follow-up study on the health and physical and mental capacity of Finnish professional firefighters (Punakallio et al., 1999). Altogether 36 of 69 firefighters in three age groups (33–38, 43–48 and 53–56 years) were asked to volunteer for this study. First 12 randomly selected subjects in each age group were asked to volunteer. Six firefighters over 50 years of age were excluded because they had had

Results

When the path was spread with water and detergent, two subjects in the older age group slipped 4 cm, and the sliding movement and balance was well controlled. After the track was made slippery with glycerol, every subject slipped in the tests at both walking cadences. Half of the subjects slipped over 5 cm in the test (Table 2). The average values of the slip distances were 9.7 ± 9.1 cm (100 steps/min) and 15.6 ± 18.2 cm (120 steps/min) in the 33-to-38-year age group and 10.8 ± 15.3 cm and 18.0 ± 18.6 cm,

Discussion

The main findings of this study were that fast and controlled performance in the dynamic stability test was related to smaller (slip distance <5 cm) risk of slipping and falling, but the associations between muscular capacities and the risk of slipping were not significant. These associations were the same for both age groups. The older firefighters tended to have longer and more serious slips than the younger ones, but the difference was not statistically significant. Furthermore, half of the

Conclusion

The younger and older firefighters of our study experienced as many slips, and half of both groups experienced over 5 cm foot slides considered to increase the risk of an unavoidable fall. Older firefighters, however, tended to have longer slip distances than the younger ones at a faster walking speed in particular. The firefighters whose slip distance was over 5 cm performed significantly poorer in the dynamic stability test as well, whereas associations between muscular capacity and the risk of

Acknowledgments

The authors wish to thank Professor Veikko Louhevaara and docent Pertti Era for their valuable comments during the preparation of this manuscript. We also thank Dr. Ritva Luukkonen for her advice regarding the statistical methods. The Fire Protection Fund of Finland and the Finnish Work Environment Fund supported this study financially.

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