A well-developed anaerobic system is important for success in swimming, particularly in sprint and middle distance events (14). Nevertheless, the relative contribution from aerobic and anaerobic energy pathways differs between such events. For example, the contribution of the anaerobic pathways to adenosine triphosphate (ATP) resynthesis falls from around 85% during a 50-yd race-paced swim to 67% during 100 yds (5), to 34% during 200 m (8), and to 18% during 400 m (14) with blood lactate concentration the highest after distances of 100 and 200 m (26).
As a result of the substantial contribution of nonmitochondrial ATP resynthesis during events of 200 m or less, proton (H+) production increases. If buffering mechanisms or transport mechanisms of the cell are compromised, then H+ will accumulate in the muscle cell leading to acidosis (20). Given that the rise in H+ concentration is accompanied by an increase in lactate concentration (12,13), it is little surprise that an elevated blood lactate concentration is associated with impaired subsequent exercise performance (10) and various metabolic perturbations (9,11). Importantly, the greatest accumulation of H+ is seen with high-intensity exercise lasting between 1 and 10 minutes (4), which is typical of the time frame for sprint and middle distance swimming (15).
Given that an elevated pre-swim blood lactate concentration is associated with a slower subsequent swimming velocity (3,7), it is not surprising that coaches have looked at ways to expedite the removal of blood lactate between multiple competitive swimming events on a single day. The limited swimming research in this area has tended to focus on passive out-of-water vs. recovery swimming (active) and has found active recovery to be better at reducing blood lactate than a passive out-of-water recovery (7,17,22–25). Additionally, swimming at lactate threshold (LT) velocity (LTv) has been shown to enhance the removal of blood lactate compared with swimming above or below LTv (7). However, as the blood LT is sensitive to training (10), the accurate determination of LTv necessitates frequent blood lactate testing. If the assessment of this threshold is not a routine part of a swimmer's training program, assigning a post-race recovery swimming velocity based on the LTv is impossible. Because of logistical constraints, such assessments are not commonplace in club or regional-level English swimming (Amateur Swimming Association of England [ASA], personal communications, December 2009). Consequently, an alternative means of assigning post-race recovery swimming velocity must be sought for these and similar swimmers.
In England, such recovery protocols typically consist of either a coach-prescribed swimming recovery or a self-paced continuous steady rate swim (ASA, personal communications). However, not all championships are held at facilities where a swim down pool is available. In this situation, land-based recovery activities consisting of light-intensity walking, skipping, and stretching are usually undertaken as an alternative means of facilitating blood lactate removal (ASA, personal communications). Whether the removal of blood lactate is facilitated more in response to one of the recovery protocols is not known. Determining the answer to this question will provide coaches and swimmers with practical information and, where the choice exists between swimming-based and land-based recovery activities, will help swimmers and coaches to choose the most appropriate recovery strategy.
Thus, the aim of the present study was to compare the effects of 2 typically administered swimming recovery protocols (self-paced continuous steady rate swimming and an adapted warm-up) and 1 land-based recovery protocol on blood lactate removal in highly trained youth swimmers after race-paced swimming. Given that light walking and stretching have a lower metabolic demand than swimming (1) and that immersion itself induces hydrostatic fluid shifts beneficial for blood lactate removal (3), it was hypothesized that blood lactate clearance would be greater in the swimming protocols than the land-based protocol but that no difference would exist between the 2 swimming protocols.
Experimental Approach to the Problem
Studies have shown that an active swimming recovery removes more blood lactate than a passive out-of-water recovery (7,17,22–25). Additionally, swimming at rather than above or below the blood LT expedites the removal of blood lactate (7). Basing a recovery on LTv, however, is only viable if the blood LT is regularly assessed. If such testing is not routinely undertaken, then an alternative method of assigning post-race recovery swimming intensity is needed. As blood LT testing is not common practice in English club or regional-level swimming, coaches typically advise swimmers to undertake either a self-paced continuous steady rate swim or a modified warm-up consisting of various strokes, intensities, and rest intervals: This differs from the percentage of maximum velocity approach. However, not all competitions are held at venues where a swim down pool is available. As an alternative, coaches advise a land-based recovery, which typically consists of light-intensity walking, stretching, and skipping (ASA, personal communications). How effective each recovery protocol is at removing blood lactate is unknown. Given that an elevated blood lactate concentration is associated with a slower subsequent swim time (3,7), determining if one recovery protocol removes more blood lactate than another is of practical importance to coaches and swimmers. Indeed, such knowledge will permit swimmers (and coaches) to gain a better understanding of recovery protocols and hence inform their decision about the type to adopt. The present study was therefore designed to mimic the recovery protocols currently used during club and regional-level English competitions and was developed in collaboration with the ASA.
Thirty-three (18 males) youth swimmers gave informed written consent to participate in this study. Where swimmers were younger than 18 years, parental/guardian informed written consent was given in addition to written child assent. Subjects were informed before the study that they had the right to withdraw at any time. The subjects' mean ± SD values for age, body mass, and height were 15.8 ± 1.7 years, 65.9 ± 7.7 kg, and 1.73 ± 0.07 m, respectively. All swimmers were free from cardiorespiratory disease, as determined by a health history questionnaire, and were well-trained competitive swimmers forming part of the South East Regional Team. Relative swimming standard was similar between swimmers along with training volume. Testing took place over the course of a year with swimmers in a mini-taper. Swimmers were asked to maintain their normal dietary habits and to ensure that they were well hydrated before testing (guidance was given on how to assess this). Institutional ethical clearance was received before the start of the study.
An independent group study design was adopted with swimmers randomly allocated to 1 of 3 groups. Each group was assigned a different 20-minute recovery protocol to be completed after a race-paced 200-m swim. The recovery protocols and demographic information of each group can be found in Table 1. The swimmers completed their race-paced swim from a dive start in their main 200-m event. Each 200-m event was represented in this study with 12 swimmers undertaking front crawl (FC), 7 swimmers undertaking backstroke (BK), 7 swimmers undertaking breaststroke (BR), 5 swimmers undertaking butterfly (FLY), and 2 swimmers undertaking an individual medley (IM). Because allocation to recovery protocols was random, the number of swimmers completing the 200-m race-paced swim using FC, BK, BR, FLY or completing an IM differed between recovery protocols (Table 1). However, as similar anaerobic and aerobic energy contributions occur between the 4 swimming strokes during 200-m swimming (5,26), this difference was deemed acceptable. Testing was completed over the course of a year, at the same time of day, and in the same 50-m pool (pool temperature was 29.1 ± 0.5° C). Swimmers began their recovery protocol within 2–3 minutes of the post-swim blood lactate sample being taken. It should be noted that unlike the coach-prescribed and land-based protocols, where strict instructions and timings were adhered to (Table 1), the only instructions given to the self-paced recovery swimming group was to complete a 20-minute continuous steady rate swim (pacing clocks were available to aid the swimmers). This contrasts with the coach-prescribed protocol where the required pacing was associated with a rating of perceived exertion (RPE) of 10–12 and a heart rate range of 40–50 b·min−1 below maximum.
Blood lactate concentration was measured from the fingertip and assessed using a portable blood lactate analyzer (Lactate Pro; Accusport, Arkray, Japan): High correlations (r > 0.96) and good levels of agreement have been reported between the Lactate Pro and other blood lactate analyzers across the physiological range of 1.0–18.0 mmol·L−1, thereby supporting its use in the sport science field (19). Before a fingertip blood sample being taken, the swimmer's hand was dried and the finger was cleaned with an alcohol wipe. All samples were taken from the middle finger of the left hand. The first drop of blood was disregarded. Blood lactate concentration was measured before each swimmer's race-paced swim, 1 minute after each swim, and approximately 60 seconds after the completion of the recovery activity.
As parametric assumptions were met (Shapiro-Wilks test, p > 0.05), a mixed-design analysis of variance was used to compare blood lactate concentration within trial (baseline, post 200-m swim, and post recovery) and between protocols (self-prescribed, coach prescribed, land based). Where differences were found, pairwise comparisons were used to assess for differences within trials (baseline, post 200-m swim, and post recovery), and independent t-tests were used to assess for differences between protocols (self-prescribed, coach prescribed, land based): Bonferroni's corrections were applied. Observed power and effect sizes (Cohen's d) were calculated where relevant. Accordingly, an effect size of up to 0.2 was deemed small, 0.5 medium, and 0.8 or above large (6). The SEM and the upper and lower limits of the 90% confidence interval (90% confidence limits) were also calculated. An alpha level of 0.05 was set a priori for statistical significance. All statistical analyses were conducted using Data PASW 18 (SPSS, Inc., Chicago, IL, USA), and data are expressed as mean ± SD.
Differences in blood lactate concentration were observed across time (F = 243.763, p = 0.000, observed power 1.000) and between time and protocol (F = 3.520, p = 0.012, observed power 0.837). Specifically, blood lactate was the highest after 200-m race-paced swimming and subsequently declined toward baseline after each recovery protocol (Table 2). When the impact of recovery protocol was examined, no differences (p > 0.05) were observed in blood lactate concentration between the 3 recovery protocols at baseline or after 200-m race-paced swimming (Table 2). Similar post-recovery blood lactate concentrations were observed between the self-prescribed and coach-prescribed recovery protocols (t = 1.0798, p = 0.294), but blood lactate concentration was higher after the land-based recovery protocol when compared with the self-prescribed (t = 2.693, p = 0.014, d = 1.17) and coach-prescribed (t = 3.689, p = 0.002, d = 1.40, Table 2) recovery protocols.
The aim of this study was to compare blood lactate removal between 3 recovery protocols (self-prescribed, coach prescribed, and land based) after race-paced 200-m swimming. The recovery protocols were designed to mimic those currently in use at club and regional-level English swimming competitions and to provide a practical alternative to LTv and percentage maximum velocity–derived approaches. The results demonstrated that lactate removal was similar between self-paced continuous steady rate swimming (self-prescribed) and a swimming recovery protocol consisting of various modes, intensities, and rest intervals (coach prescribed) but was reduced when light-intensity walking, skipping, and stretching only (land-based) were used (Table 2). Specifically, blood lactate concentration fell by 81 and 83% in response to self-prescribed and coach-prescribed recovery swimming, respectively, but fell by only 66% after the land-based recovery.
To date, studies employing active recovery sets have based recovery pace on the LTv (7) or assigned a percentage of maximum swimming velocity (16,22,24). As the former requires frequent blood lactate testing, which can be cost and logistically prohibitive, basing the recovery activity around swimming effort or swimming velocity may be more appealing to coaches and swimmers. Where recovery velocity is based on a percentage of maximum swimming velocity, studies have shown similar blood lactate clearance rates when velocities of 50–75% (based on 25- or 100-m distances) of maximal are adopted (16,22,24). Moreover, the most comfortable velocity is reported to be around 65% of maximum velocity (16,22) during recovery swims of 6–15 minutes. It is therefore not surprising that when free to choose a recovery, swimming pace swimmers tend to adopt a velocity of 60–70% of maximum (15,22). It is thought that slower velocities interfere with stroke mechanics (22), whereas faster paces increase the metabolic stress placed on the body and potentially retard blood lactate removal (2).
Because achieved velocity was not recorded during the self-paced recovery, it is not possible to determine the actual swimming pace adopted. Conversely, the coach-prescribed protocol was designed to reflect workloads associated with an RPE of 10–12 and a heart rate range of 40–50 b·min−1 below maximum. Despite the protocol differences between the self-prescribed and coach-prescribed recovery activities, both were associated with a similar magnitude of blood lactate removal (81 and 83%, respectively), which was greater than that observed in previous studies (66–70%) using a swimming velocity associated with 65% of maximum velocity or LTv for 10 or 20 minutes after race-paced 200-yd swimming (7,17). Interestingly, the actual post-swim blood lactate concentrations were quite variable between these studies ranging from 9.5 to 10.6 mmol·L−1 (7) and 2.4 to 13.2 mmol·L−1 (17). It is not clear why such differences in post-swim blood lactate concentration occurred or why the range was so large in the case of the study by Neric et al. (17). For example, swimmers were of a similar age (17–20 years) and standard, and the same make of blood lactate analyzer was used. However, the mean body mass of participants varied considerably between the studies. It is also possible that temperature and nutritional status also varied.
Given that lactate removal is dependent on skeletal muscle blood flow (2), it is no surprise that blood lactate clearance was slower (p < 0.05) in the land-based protocol compared with self-prescribed and coach-prescribed protocols (Table 2). Indeed, as 85% of the land-based recovery consisted of very light intensity activity (75%) or rest (10%), and only 15% consisted of moderate-intensity exercise (skipping) (Table 1), one would expect the metabolic demands (1) and in turn blood flow to the working muscles to be less when compared with either swimming recovery (21). In addition, the hydrostatic compressive forces induced by immersion cause fluid shifts (3) and an increase in blood flow (18), which should enhance blood lactate removal (2,3). Such differences between the water-based and out-of-water recovery protocols most likely explain the large effects sizes observed when the land-based recovery was compared with the self-prescribed (d = 1.17) and coach-prescribed (d = 1.40) recovery swims.
Based on the findings of Greenwood et al. (7), it seems likely that the reduced rate of blood lactate removal in the land-based recovery would negatively impact subsequent 200-m performance when compared with self-prescribed and coach-prescribed protocols. Greenwood et al. (7) demonstrated that if blood lactate is elevated before a race-paced 200-yd swim, the magnitude of elevation has significant implications for swimming velocity. They found that a blood lactate concentration of 3.8 mmol·L−1 (which is similar to that observed after the land-based recovery, Table 2) was associated with a slower mean swim time of 1.67 s (p < 0.001) compared with a blood lactate concentration of 3.1 mmol·L−1. They also showed that the magnitude of blood lactate removal can account for up to 24% of subsequent swimming time trial performance. Whether similar coefficients of determination are evident in different swimming events is difficult to determine as the impact of an elevated blood lactate concentration on performance does appear to be affected by swimming distance and recovery duration (3,24). Nevertheless, a difference in swim time of less than 2 seconds can determine whether a swimmer wins or loses a race or whether they progress from a heat to a final.
It is not possible to determine if the land-based recovery removed more blood lactate than a passive recovery (i.e., a control group) as the latter was not included in the present study. However, results from previous studies using recovery durations of 15–20 minutes suggest that a land-based recovery would remove more blood lactate than a passive recovery (17,25). Although the aim of the present study was to examine current practice and hence maximize ecological validity, the lack of a control group is nevertheless a limitation but does not detract from the practical usefulness of the findings. Indeed, the protocols assessed provide swimmers with a practical alternative to using either percentage of maximum velocity or LTv-derived recovery swims. It is also not possible to determine the impact of immersion alone on blood lactate clearance, which is known to induce fluid shifts (3) and enhance perfusion (18). It can also be argued that because swimmers in the present study were tested over the course of a year rather than a matter of weeks, they might have been in different training phases at the time of testing. To counteract this, participants were randomly assigned to 1 of the 3 protocol groups and were in a mini-taper. In addition, baseline and post-swim blood lactate levels were similar between groups (Table 2), which also indicates that the unbalanced distribution of FC, BK, BR, FLY, and IM 200-m swimmers between the 3 protocol groups was unlikely to have confounded the results. It should also be noted that unequal numbers of males and females undertook the recovery activities (Table 1). Although the blood lactate response to exercise can differ between males and females (26), blood lactate concentration was similar after race-paced 200-m swimming in all 3 groups (Table 2). This suggests that the unequal number of males and females per group had little impact on the mean blood lactate response.
In conclusion, the findings of the present study offer an alternative to assigning swimming recovery protocols based on the LTv or percentage of maximum velocity. Not only are the swimming recoveries in the present study likely to be simpler for swimmers to follow (particularly the self-prescribed protocol), but are also reflective of current practice in club and regional-level English competitions. Importantly, both swimming recovery protocols removed significantly more blood lactate than the land-based protocol, which resulted in a blood lactate concentration similar to the desired pre-swim concentration of less than 2 mmol·L−1 (26). Whether swimmers choose to adopt a self-prescribed or coach-prescribed swimming protocol does not appear to be of practical importance. However, where facilities permit, either protocol should be prioritized over a land-based protocol.
This study demonstrates that blood lactate removal is similar after a 20-minute swim regardless of whether well-trained youth swimmers self-select a continuous steady rate pace (self-prescribed) or undertake a modified warm-up consisting of different swimming modes, intensities, and rest intervals (coach prescribed). Furthermore, both types of active swimming recovery removed more blood lactate than a similar duration land-based recovery consisting of light-intensity walking, skipping, and stretching. Although the 3 recovery protocols are typical of those used during club and regional-level English swimming competitions, coaches and swimmers are advised to employ a self-prescribed or coach-prescribed recovery swim similar to that adopted in the present study rather than a land-based recovery activity. Only when a cool down pool is not available should a land-based protocol consisting of light-intensity walking, skipping, and stretching be adopted.
The author thanks the Amateur Swimming Association of England for their financial support of this study. The author also wishes to thank the swimmers and coaches for their participation and Dr. Jo Corbett for his helpful comments in the preparation of this article.
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