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Occupational Medicine Advance Access originally published online on November 2, 2005
Occupational Medicine 2006 56(1):12-17; doi:10.1093/occmed/kqi168
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© The Author 2005. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Occupational fitness standards for beach lifeguards. Phase 2: the development of an easily administered fitness test

T. Reilly1, C. Iggleden1, M. Gennser2 and M. Tipton1

1 Department of Sport and Exercise Science, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth PO1 2DT, UK
2 FOI, Karolinska Institute, Stockholm, Sweden

Correspondence to: T. Reilly, Department of Sport and Exercise Science, Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth PO1 2DT, UK. Tel: +44 23 9284 2435; fax: +44 23 9284 2641; e-mail: tara.reilly{at}port.ac.uk


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background No task-based fitness standard currently exists for beach lifeguards (BLGs).

Aim To formulate an easily administered fitness test for BLGs based on the physical demands identified in Phase 1 of the project (previous paper).

Methods A range of anthropometric and land- and water-based (swimming pool and flume) fitness assessments were administered to 25 male and female volunteer subjects (13 BLGs from the UK).

Results The mean (SD) VO2max (l/min) were 3.04 (0.61) for towing a casualty, 2.08 (0.53) for board paddling with a casualty and 2.97 (0.67) for freestyle swimming. A significant correlation (r = –0.82, P < 0.001) was identified between distance paddled in the sea in 3.5 min (established in Phase 1) and pool 400-m front crawl swim time and between towing VO2max and deltoid circumference/log10 400-m front crawl swim time (r = –0.83, P < 0.001).

Conclusions The regression identified allows the conclusion that if a BLG can swim 400-m front crawl in a pool in <7.5 min, he/she should be able to paddle 310 m in the sea in <3.5 min. Final recommendations for a fitness test for potential BLGs are presented.

Keywords      Fitness standards; lifeguarding; occupational fitness; rescue


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
In Phase 1 of this project [1] the most physically demanding generic critical tasks associated with beach lifeguarding were established and characterized. No specific, validated and easily administered tests exist that predict the performance of individuals on the critical tasks associated with beach lifeguarding, and the direct measurement of aerobic power involves considerable time, expense and technical expertise, and is impractical for large groups of people.

Jackson et al. [2] established a correlation of 0.898 between the distance covered during a 12-min front crawl swim and the endurance and peak aerobic power (VO2max) results obtained from tethered, multi-stage swimming test time to exhaustion. Conley et al. [3] attempted to validate the 12-min swim test by direct comparison with oxygen consumption measured during tethered swimming and concluded that it had relatively low validity as a field test of peak aerobic power. Lavoie et al. [4] described a multi-stage swim test for competitive swimmers that correlates well (r = 0.877) with oxygen consumption up to maximal levels. However, its usefulness is limited for subjects with more variable swimming ability. Costill et al. [5] have reported that the best predictors of VO2max for trained swimmers are lean body mass and stroke index (distance per stroke, r = 0.97). These predictors have not been tested with mixed-ability swimmers.

In this phase of the project, the objective was to establish if performance on the critical rescue tasks of paddling and casualty towing could be predicted for beach lifeguards (BLG) from a combination of pool-based tests and anthropometric measures, thereby establishing a minimum fitness standard.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
Thirteen BLGs, 10 of whom had completed the previous phase of the project, and 12 other subjects, 8 of whom were lifeguards from Sweden, constituted the 25 volunteers for this phase. The protocol was approved by the Ethical Committees of both the Karolinska Institute and University of Portsmouth.

Height (cm), mass (kg), arm length (cm, acromion to mid dactylion), shoulder circumference (cm, greatest width mid-deltoid), chest circumference (cm, nipple height), percentage body fat (Durnin and Womersley [6]), surface area and body mass index [7] were measured with subjects wearing a swimming costume.

Subjects performed a multi-stage shuttle run to estimate VO2max [8] and as many standardized push-ups as they could in 60 s.

Each subject was given the opportunity to familiarize himself/herself with the swimming flume (temperature 20°C). Throughout these tests subjects wore a nose clip and breathed through a mouthpiece (Spirotechnique, France) into respiratory tubing. The subjects wore their lifeguarding swimming costume. Each subject undertook three tests to VO2max:

(i) Towing test: following 4 min of self-paced towing, the velocity of the flume was increased every 0.5–1 min by 0.05–0.1 m/s until volitional exhaustion. The subjects towed a 50-kg marine anthropometric manikin (designed to float in the water as an unconscious 50th percentile male) using a rescue tube secured around the chest of the manikin.
(ii) Paddle test: following 4 min of self-paced paddling, the velocity of the flume was increased every 0.5–2 min by 0–0.2 m/s until volitional exhaustion. Subjects paddled prone with the manikin on the rescue board (Figure 1).
(iii) Front crawl test: subjects swam in the flume using front crawl. Following 4 min of self-paced swimming, the velocity of the flume was increased every 0.5–2 min by 0.1–0.2 m/s until volitional exhaustion.



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  		Figure 1. Subject rescue paddling in the swimming flume.

 
Oxygen consumption was recorded breath-by-breath using a Metamax 3B analyser (Cortex Biophysik, Germany). Effort was monitored by blood lactate sampling measured from a fingerprick blood sample 3 min after cessation of all maximum efforts in the flume and pool (ProTest meter, Arkray Inc., Japan).

Following a warm-up period, the following timed tests were performed in a 25-m swimming pool:

(i) Four-hundred-metre front crawl: the number of strokes taken during the 2nd, 8th and 15th laps was recorded.
(ii) Three-hundred-metre breast-stroke.
(iii) Two-hundred-metre one-armed breast-stroke: subjects swam 200-m breast-stroke at maximal effort while holding onto a swimming float with one arm. They were permitted to alternate arms. The test was designed to replicate swim towing with a casualty.
A minimum of 30 min elapsed between consecutive tests. Maximum effort was monitored by blood lactate sampling.

Having established that the necessary assumptions had been met, data were analysed using Student's t-test, Wilcoxon's signed-rank test and Pearson's product moment correlation coefficient with Minitab® 13. Variables with the greatest degree of association were investigated further using linear regression analysis. P < 0.05 unless stated otherwise.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
The physical characteristics of the subjects are presented in Table 1.


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  		Table 1. Physical characteristics of UK and Swedish subjects

 
The results obtained from the swimming flume are presented in Table 2. The oxygen consumption recorded during towing and swimming did not differ significantly; both were higher than those seen during paddling. The mean blood lactate levels (SD) recorded following towing and swimming were 8.5 mmol/l (1.8) and 7.1 mmol/l (2.8), respectively; both were higher than the levels seen following paddling (arm-only exercise), 6.9 mmol/l (2.3).


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  		Table 2. Oxygen consumption at a self-selected pace and VO2max during paddling, towing and swimming in the flume

 
The results obtained in the pool are presented in Table 3. Data are presented, and were analysed, for all of the subjects and separately for the UK BLG only.


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  		Table 3. Time (seconds) for front crawl and breast-stroke (one and two armed) swimming in the pool

 
The most significant correlations obtained between the variables measured in the present study are shown in Table 4.


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  		Table 4. Significant (P < 0.001) correlations obtained in present project (n = 23 unless otherwise stated, n = 13 for ‘BLG only’)

 
None of the land-based tests of strength or fitness predicted performance of BLG on their critical tasks.

On the basis of the correlation between distance paddled in 3.5 min in the sea and the time taken to swim 400 m in the pool, a regression equation was identified (r = 0.72, P < 0.001, n = 13 BLG) in which the distance paddled to a casualty in 210 s equalled:

From this a BLG should be able to paddle 310 m in the sea in <3.5 min provided he/she can swim 400-m front crawl in a pool in <7.5 min. Ninety-one per cent of the present subjects achieved this time.

Maximum aerobic capacity during towing was most closely associated with VO2max during swimming, swimming performance and anthropometric measures (see footnote b in Table 4). As the measurement of both swimming VO2max and lean body mass require specialist methods, the relationship between deltoid (shoulder) circumference, swimming performance and towing VO2max was explored further. It was determined that tow VO2max (l/min) and [deltoid circumference (cm)/log10 400-m swim time (s)] had an r value of 0.83. The regression equation being:

The relationship is primarily determined by deltoid circumference; deltoid circumference (cm) and tow VO2max (l/min) (BLG only) correlated with an r value of 0.76.

In the flume, a 0.1 m/s increment in towing velocity required an increase of 0.35 l/min in oxygen consumption. The average towing velocity of subjects at self-selected pace was 0.4 m/s, and this required them to work at 70% of their VO2max (see Table 2). In fit, trained but non-elite athletes this is as high a percentage as is recommended to work to avoid excessive anaerobic metabolism and fatigue [9–12].

The requirement to return a casualty to the beach within 10 min [1] leaves a maximum of 6.5 min to return them to the shore. The maximum distance a BLG would need to cross-chest tow an unconscious casualty is 100 m, as at this point other lifeguards would have come to assist in rescue boats. To cover 100 m in 6 min (assuming 30 s for securing the casualty) requires a towing speed of 0.28 m/s. From the relationship between tow speed and tow oxygen consumption, an average tow speed of 0.28 m/s requires an oxygen consumption of 1.7 l/min. This should not represent >70% of towing VO2max, which must therefore be 2.43 l/min. This towing VO2max corresponds to a deltoid circumference/log10 400-m swim time of 41. Eighty-nine per cent of the subjects tested achieved this standard.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
Our findings suggest that the performance of critical rescue tasks of paddling and casualty towing can be predicted from a combination of pool-based tests and anthropometric measures.

Swimming VO2max was strongly associated with both paddling (r = 0.84) and towing VO2max, but is difficult to measure. Attempts have been made to develop simple, indirect tests and indices that predict swimming aerobic power and performance, including simulated swimming [13], a multi-stage swim test [4], measurement of energy expenditure [5], a 12-min swim test [2,3], upper body anaerobic power [14] and arm stroke index [15]. Costill et al. [5] reported that the best predictors of VO2max for trained swimmers are lean body mass and stroke index (distance per stroke). In the present study, with mixed-ability swimmers, the stroke index did not correlate with swimming, paddling or towing VO2max.

It was not possible to identify a land-based, indirect assessment of running VO2max (shuttle run) that would predict swimming, towing or paddling VO2max. This is in contrast to the findings of Magel and Faulkner [16] who found that the VO2max recorded in tethered swimming and treadmill running were highly correlated. It is noted that these authors tested highly trained college swimmers, and others have reported that VO2max can be anything from 75 to 100% of running VO2max, depending on the skill level of the swimmers [17,18].

Upper body anaerobic power has been reported to predict swimming performance in swimming events up to 400 m [14]. The correlations obtained in the present study between towing VO2max and both upper body anthropometric measures (e.g. deltoid circumference) and push-ups support the conclusion that upper body strength is an important characteristic for rescue swimming. It would therefore be beneficial to encourage potential recruits to develop their upper body strength and endurance.

At first sight, the lack of a relationship between the pool (swim time) and flume (oxygen consumption during swimming) performance appears surprising. Past research indicates that flume swimming, free swimming and tethered swimming elicit a similar VO2max [19]. However, higher values have been reported during free swimming [16] and Costill et al. [5] note little relationship between VO2max and 400-yard front crawl performance: despite almost identical oxygen consumptions, recreational swimmers swim significantly slower than competitive swimmers due to large differences in swimming efficiency. Differences in body attitude and hydrodynamics between flume, free and tethered swimming make a direct comparison between these forms of exercise in terms of work efficiency difficult [16].

On the basis of the results of this and the previous study [1] the following task-related tests are recommended:

(i) Pool swim of 400 m in <7.5 min—to predict paddling performance.
(ii) Pool swim of 200 m in <3.5 min—to predict sea swimming performance.
(iii) Twenty-five-metre underwater swim immediately followed by 25-m surface swim; complete in <50 s—to assess confidence under the water and swimming efficiency.
(iv) Lift 41 kg torso manikin with both arms and move backwards 10 m (appropriate training in manual handling to be provided prior to lift).
Additional tests to be used for guidance and preparation only:
(i) Candidate's deltoid circumference (cm) to be measured and divided by the log10 of his/her 400-m front crawl swim time (s). Resulting number to exceed 41.
(ii) Two-hundred-metre beach run as fast as possible; complete in <40 s.
(iii) Push-ups: males to achieve 37, females 15 in 1 min, resting permitted within the minute.
(iv) A 2.4-km run to achieve ‘good’ or above according to published norms [males aged 20 years ‘good’ = 3.55 l/min (52 ml/kg/min); females aged 20 years ‘good’ = 2.3 l/min (43 ml/kg/min)] [20]. Potential male recruits should train so that they can run 2.4 km in 10 min 15 s and no slower than 11 min 44 s. Potential female recruits should train so that they can run 2.4 km in 11 min 56 s and no slower than 14 min 24 s.
The tests should not be used in isolation, as success in one test does not guarantee adequate physical fitness for beach lifeguarding. The tests are related to fitness required to undertake a task, not the level of skill.


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
Thanks to David Salt for help with the statistics. The project was funded by the Royal National Lifeboat Institution.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

  1. Reilly T, Wooler A, Tipton M. Occupational fitness standards for beach lifeguards. Phase 1: the physiological demands of beach lifeguarding. Occup Med (Lond) 2006;56:6–11.[Medline]

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  3. Conley D, Cureton K, Dengel D, Weyand P. Validation of the 12-minute swim as a field test of peak aerobic power in young men. Med Sci Sports Exerc 1991;23:766–773.[Medline]

  4. Lavoie J, Leger L, Leone M, Provencher P. A maximal multistage swim test to determine the functional and maximal aerobic power of competitive swimmers. J Swim Res 1985;1:17–22.

  5. Costill D, Kovaleski J, Porter D, Kirwan J, Fielding R, King D. Energy expenditure during front crawl swimming: predicting success in middle-distance events. Int J Sports Med 1985;6:266–270.[Medline]

  6. Durnin J, Womersley J. Body fat assessed from total body density and its estimation from skinfold thickness: measurements on 481 men and women aged from 16–72 years. Br J Nutr 1974;32:77–90.[CrossRef][ISI][Medline]

  7. Du Bois D, Du Bois EF. The measurement of the surface area of man. Arch Intern Med 1915;15:868–881.[ISI]

  8. Leger LA, Boucher R. An indirect continuous multistage field test: The Universite de Montreal tract test. Can J Appl Sport Sci 1980;5:77–84.[Medline]

  9. Wasserman K, Whipp BJ, Davis JA. Respiratory physiology of exercise: metabolism gas exchange and ventilatory control. Int Rev Respir Physiol 1981;23:149–211.

  10. Whipp BJ. The slow component of O2 uptake kinetics during heavy exercise. Med Sci Sports Exerc 1994;26:1319.[ISI][Medline]

  11. Wilbur RL, Zawadzki KM, Kearney JT, Shannon MP, Disalvo D. Physiological profiles of elite off-road and road cyclists. Med Sci Sports Exerc 1997;29:1090.[Medline]

  12. Tschakovsky ME, Hughson RL. Interaction of factors determining oxygen uptake at the beginning of exercise. J Appl Physiol 1990;86:1011.

  13. Kimura Y, Yeater RA, Martin RB. Simulated swimming: a useful tool for evaluation the VO2max of swimmers in the laboratory. Br J Sports Med 1990;24:201–206.[Abstract]

  14. Hawley J, Williams M. Relationship between upper body anaerobic power and freestyle swimming performance. Int J Sports Med 1991;12:1–5.[Medline]

  15. Lavoie JM, Leone M. Functional maximal aerobic power and prediction of swimming performances. J Swim Res 1988;4:17–19.

  16. Magel JR, Faulkner JA. Maximal oxygen uptake of college swimmers. J Appl Physiol 1967;22:929–938.[Free Full Text]

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  18. McCardle WD, Katch FI, Katch VL. Exercise Physiology. 4th edn. Williams and Wilkins, 1996.

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This Article
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