a b s t r a c t

Purpose: The aim of this study is to compare the effectiveness of active recovery in form of running or foam rolling on clearing blood lactate compared to remain sitting after a water rescue.

Method: A quasi experimental cross-over design was used to test the effectiveness of two active recovery methods: foam rolling (FR) and running (RR), compared with passive recovery (PR) on the blood lactate clear- ance after performing a water rescue. Twelve lifeguards from Marin (Pontevedra) completed the study. The par- ticipants performed a 100-meter water rescue and a 25-minute recovery protocol.

Results: The post recovery lactate levels were significantly lower for foam rolling (4.4 +- 1.5 mmol/l, P = 0.005, d

= 0.94) and running (4.9 +- 2.3 mmol/l, P = 0.027, d = 1.21) compared with resting (7.2 +- 2.5 mmol/l); there was no significant difference between foam rolling and running (P = 1.000).

Conclusions: We found that surf lifesavers clear out blood lactate more efficient when performing an active recov- ery protocol. Foam rolling is an effective method of increasing the rate of blood Lactate clearance. These two re- covery methods are also adequate for surf lifeguards as they do not interfere with the surveillance aspect of their job.

(C) 2017

Introduction

The fight against drowning is one of biggest current challenges in public health. The World Health Organization estimates that around 372,000 persons drowns every year, being one of the leading death causes for Young people [1].

A drowning is a time critical situation as cardiac arrest normally oc- curs only minutes after immersion [2]. The drowning timeline [3] is a new model to understand the drowning process, establishing 3 phases: pre-event, event, and post-event. When the drowning occurs and the victim is in distress, the lifeguard has to react as fast as possible to initi- ate the rescue and therefore be able to mitigate the incident. Higher chances of survival have been associated with victim submersion

* Corresponding author at: REMOSS (research group), Faculty of Education and Sport Sciences, University of Vigo, Campus de A Xunqueira s/n, CP: 36005 Pontevedra, Spain.

E-mail address: [email protected] (A. Perez-Ferreiros).

times lower than 10 min [4-6]. The quality of a water rescue therefore depends largely on how fast it is performed.

The most common distance at which drowning occurs, is between 50 and 100 m from the shore [7,8]. Some studies have shown that surf lifeguards needs around 5 min to rescue a victim 75-100 m from shore [9,10]. This is a physically exhausting task that results in very high blood lactate concentrations of over 10 mmol/l [9,10].

It is not uncommon that several water rescues must be performed during a single day and beach [8]. The lifeguards’ ability to perform mul- tiple rescues during the working day with maintained quality relies on their ability to recover effectively after performing a rescue [11,12]. The lifeguards’ safety is of uttermost importance during the rescues [13], this is dependent on their ability to maintain the physical condi- tioning for subsequent rescues.

To our knowledge, no attempts to investigate how to optimize the recovery of surf lifeguards after water rescues has been made. The aim of this study is therefore to compare the effectiveness of active recovery

http://dx.doi.org/10.1016/j.ajem.2017.06.028

0735-6757/(C) 2017

in form of running or foam rolling on clearing blood lactate compared to remain sitting after a water rescue.

Method

A quasi experimental cross-over study design was used to test the effectiveness of two active recovery methods: foam rolling (FR) and running (RR), compared with passive recovery (PR) on the blood lactate clearance after performing a water rescue (Fig. 1).

Sample

Thirteen surf lifeguards from Marin, Pontevedra, Spain participated in the experiment. Twelve participants (age: 24 +- 4.9 years, height: 175 +- 7.1 cm, weight: 74 +- 10.0 kg, BMI: 24.0 +- 2.5) completed all re- covery methods and was therefore included in subsequent analyses. All participants gave their written informed consent prior to the study. The research was approved by the Ethical Committee of the Faculty of Edu- cation and Sport Sciences (University of Vigo, Spain), in accordance with the Helsinki declaration.

Water rescue

The water rescue consisted of running 10 m to the water, swimming 100 m with fins to the victim, gaining control of the unconscious victim, towing the victim 100 m back to shore, and extracting the victim to dry sand [10]. The participating victims (height: 170-190 cm, weight: 70-

80 kg) were instructed to simulate an unconscious person. The rescues were performed with fins (Mares Avanti Super-Channel) that the par- ticipants had to put on when they entered the water. Wet suits (Seland Somo 3/2, Urduliz, Bizkaia, Spain) were used to minimize the impact of varying water temperatures.

The rescues were all performed at Mogor beach, Pontevedra, Spain (Latitude: 42.385442, Longitude: -8.720025) under similar conditions: Calm sea with waves b 0.5 m (Douglas scale value 0-2), wind speed b 5 m/s, water temperature ranged between 14 ?C and 15 ?C, and ambi- ent temperature between 20 ?C and 23 ?C.

The weather was reported by the local forecast agency (Meteogalicia). All rescues were performed between March 15 and 17, 2017.

Recovery

After the participants had finished the water rescue, lactate level and rate of perceived exhaustion (RPE) were collected imme- diately. Thereafter the participants were instructed to directly take off their wetsuit and start their respective recovery protocol. The total time of recovery (between measurements of lactate levels) was 25 min.

The 2 active recovery methods were chosen as they allow the life- guards to surveil the beach while performing the recovery. The passive recovery was chosen as control as it is the facto standard after performing a water rescue.

Fig. 1. Flow chart outlining the experimental design.

foam roller“>Passive recovery

The participants were instructed to remain seated during the full length of the recovery to simulate return to the watchtower.

Running recovery

The protocol was adapted from Losnegard et al. [14], as the work time and lactate levels were similar to what has been reported in 100 m water rescues with fins [10]. The RR consisted of 4 min of taking of the wet suit and walk, 16 min of running at a pace of proximately 60% of the participant’s VO_2max, and ending with 5 min of walking [14].

The participants were instructed to perform the running part at a rate of perceived exhaustion (RPE) of 5-6 out of 10 to regulate the pace. We chose to use RPE for regulating the running pace to improve applicability of the protocol, as it eliminates the need for any previous testing or apparatus during the recovery.

Foam roller

The FR protocol consisted of five exercises (Fig. 2) for the quadriceps, iliotibial tract, hamstrings, adductors and gluteus respectively [15]. All exercises were performed for 1 min on each leg; after finishing all the exercises it was repeated, with a final active time of 20 min [15]. High density foam rollers (19 x 15 cm, Trendingfit, Beriain, Spain) were used. The participants were instructed to place their weight on the foam roller at the proximal aspect of the thigh or gluteus and gradually move downwards (towards the knee or gluteal tuberosity) with undu- lating movements. When reaching the knee or gluteal tuberosity, they were instructed to return to the proximal aspect with a single move- ment, keeping their weight on the foam roller. The participants were instructed to apply sufficient bodyweight to produce a pain level of 7 out of 10 [16]. Prior to the experiment, all participants had participated in two practice sessions under the supervision of experts to ensure the

quality of the FR protocol.

Variables

The participants Blood lactate levels were measured before water rescue (baseline lactate; La1), post water rescue (La2), and post recov- ery (La3). All measurements were made with LactateScout (SensLab GmbH, Leipzig, Germany) and expressed in mmol/l. The total time of the water rescue as well as the victim time (time to gain control of, tow, and extract the victim) was recorded. Participants RPE was record- ed directly after each water rescue using the CR-10 scale [17].

Statistical analysis

The results are presented as group means with standard deviations and confidence interval. The Shapiro-Wilk test was used to test for nor- mality. Repeated measures analysis of variance (ANOVA) was used for La3, and Friedman test was used for La1, La2 and RPE; both with post- hoc pairwise comparisons using Bonferroni corrections. Effect sizes is calculated using eta-squared (?²) for ANOVA, Kendall’s W for Friedman test, and Cohen’s d for paired t-test.

IBM SPSS for Mac, version 20 (IBM Corp., Armonk, N.Y., USA) was used. Significance levels were set to P b 0.05 for all analyses.

Result

For the 36 water rescues that were performed the total time was on average 298 s (SD = 47.7, 95% CI = [281, 314]), and the victim time was on average 200 s (SD = 41.6, 95% CI = [186, 214]).

Lactate levels and RPE for each of the recovery methods, and the re- sults of ANOVA and Friedman test are presented in Table 1. The average baseline lactate level (La1) was 2.7 +- 0.9 mmol/l and rose to 10.1 +-

2.1 mmol/l after the water rescues (La2), with an average RPE of 8 +-

1.4. No significant differences between recovery methods were present for La1, La2, or RPE. The post recovery lactate levels (La3) were signifi- cantly lower for FR (4.4 +- 1.5, d = 0.94) and RR (4.9 +- 2.3, d = 1.21) compared with PR (7.2 +- 2.5 mmol/l); there was no significant differ- ence between FR and RR.

Discussion

This paper analyzed the lifeguards’ effort after a rescue, assessing dif- ferent methods that can help early physiological recovery. In drowning, every second counts. The recovery after a water rescue is important for a surf lifesaver to be able to perform a consequent rescue with as high quality and safety as possible. To our knowledge, no intent has been made to study the effects of different recovery strategies for surf life- guards, furthermore no study has investigated the effects of foam rolling on lactate clearance. Therefore, our study aimed to test if active recovery protocols, in this case running and foam rolling, improves the lactate clearance compared with return to sitting after a water rescue.

The results show that surf lifesavers clear out more lactate after 25 min if they perform active recovery in form of foam rolling or run- ning than if they remain seated after a water rescue; no difference be- tween the running and foam rolling was seen. When the lifeguards performed active recovery, they cleared out around 50% of the accumu- lated lactate from the rescue, while they only cleared out around 30% when remaining passive.

Faster lactate clearance when using an active recovery such as run- ning, swimming, or cycling has been confirmed in a variety of sporting activities [11,12,14,18]. Losnegard et al. [14] found that the relative re- duction of blood lactate concentration during recovery after a ski sprint correlates closely with performance reduction in a subsequent sprint. With work time and lactate levels closely resembling the ones reported in this and previous studies on water rescues [9,10,14], this strengthens the notion that the post-rescue recovery is important for surf lifeguards.

The effect of foam rolling has previously been studied on inter-ses- sion recovery; it has been shown to reduce pain, increase range of mo- tion and improve muscular performance 24-72 h after session [15,19]. Although it has suggested that foam rolling increase blood lactate re- moval [19], to our knowledge, this is the first study to investigate this notion. Our results showed that foam rolling helps clear out blood lac- tate as effective as traditional active recovery protocols used for this purpose. This suggests that foam also could be an effective method for intra-session recovery.

Although the relationship between active recovery and lactate re- moval is well established [11,12,14,18], studies of the influence on

Fig. 2. Foam roller exercises in order: (A) quadriceps, (B) iliotibial tract, (C) hamstrings, (D) adductors, and (E) gluteus.

Table 1

Descriptive and inferential statistics (ANOVA or Friedman test) of blood lactate and RPE.

Variable PR RR FR Test statistic^a Effect size^b P PR vs. RR PR vs. FR RR vs. FR

	Mean	SD	95% CI		Mean	SD	95% CI		Mean	SD	95% CI
La1 (mmol/l)c	2.5	0.9	1.9-3.0		2.9	1.1	2.2-3.6		2.7	0.8	2.2-3.2	0.304	0.013	0.859
La2 (mmol/l)c	10.4	2.1	9.0-11.7		10.1	2.3	8.7-11.6		9.8	2.1	8.5-11.2	0.182	0.008	0.913
La3 (mmol/l)d	7.2	2.5	5.7-8.8		4.9	2.3	3.5-6.3		4.4	1.5	3.5-5.4	7.452	0.404	0.003 0.005	0.027	1.000
RPEc	8	1.3	7-9		8	1.8	6-9		8	1.2	7-9	0.649	0.027	0.723

La1, baseline lactate; La2, post-rescue lactate; La3, post-recovery lactate; RPE, rate of perceived exhaustion at finished water rescue; PR, passive recovery; RR, running recovery; FR, foam rolling.

^a Test statistics for ANOVA: F, Friedman’s test: ?².

^b Effect size for ANOVA: eta square, Friedman: Kendal’s W.

^c ANOVA.

^d Friedman test.

subsequent performance shows mixed result [11,12,14,18,20,21]. One possible explanation is the wide variety of rest time, work types, and work times used in the studies. Another possible explanation is that the increased workload of performing the active recovery induces fa- tigue that cancels out the positive effects of reducing the blood lactate concentration. This suggests that use of less intensive protocols - such as foam rolling or massage - might be advantageous to use for intra-ses- sion recovery.

The different parts of a water rescue put different demands on the lifesaver. During the approach to the victim the lifesaver can swim freely and therefor use both upper and lower extremities to propel him or her- self; once the lifesaver engages with the victim, the mass to be transported roughly doubles, and only the lower extremities can be used. The fact that the lifesavers were engaged with the victims over 67% of the rescues supports the use of a lower-extremity foam rolling protocol.

Our results suggest that foam rolling and running facilitates post res- cue recovery for surf lifeguards, and can therefore improve their ability to carry out their work with quality and in a safe manner. These two re- covery methods are also adequate for surf lifeguards as they do not in- terfere with the surveillance aspect of their job.

Limitations

This study was restricted to measure blood lactate concentrations as indicator of recovery and did not test performance in a subsequent water rescue. We chose to focus this study on the intra-session recovery of the lifeguards; this means that we did not measure the inter-session effects of recovery methods, which is equally important as the lifesavers might have to perform a water rescue on a subsequent work day. Lastly, even though we considered practical aspects such as ability to monitor the beach during the recovery, we did not test these aspects.

Although we tried to replicate a real-life rescue, a simulated scenario is never the same as a real-world setting. All life guards in this study had experience swimming with fins, but they had different preferences re- garding auxiliary materials (rescue can or rescue tube). To eliminate this experience or preference bias, we chose to no use any auxiliary ma- terial and utilize a body to body technique with fins for the rescues.

Conclusion

We found that surf lifesavers benefit from implementing an active recovery protocol after performing a water rescue, as they clear out blood lactate more efficient and therefore might be in a better shape to perform a subsequent water rescue.

This study also indicates that foam rolling is an effective method of increasing the rate of blood lactate clearance. This provides new evi- dence that foam rolling might be an effective intra-session recovery strategy in complement to earlier proofs of its effectiveness on inter- session recovery.

To establish physiological recovery protocols for rescue teams could be an important area of study in the coming years, as it has the potential to improve the safety and quality of lifesaving.

Acknowledgment

We would like to thank the lifeguards and their instructors involved in this experiment.

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