The Effects of Training Volume and Repetition Distance on Session ...

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Purpose: To assess swimmers' session rating of perceived exertion (sRPE) after standardized sets of interval swimming training performed at the same relative ...
International Journal of Sports Physiology and Performance, 2015, 10, 848  -852 http://dx.doi.org/10.1123/ijspp.2014-0410 © 2015 Human Kinetics, Inc.

Original Investigation

The Effects of Training Volume and Repetition Distance on Session Rating of Perceived Exertion and Internal Load in Swimmers Renato Barroso, Diego F. Salgueiro, Everton C. do Carmo, and Fábio Y. Nakamura Purpose: To assess swimmers’ session rating of perceived exertion (sRPE) after standardized sets of interval swimming training performed at the same relative intensity but with different total volume and repetition distance. Methods: Thirteen moderately trained swimmers (21.1 ± 1.1 y, 178 ± 6 cm, 74.1 ± 8.3 kg, 100-m freestyle 60.2 ± 2.9 s) performed 4 standardized sets (10 × 100-m, 20 × 100-m, 10 × 200-m, and 5 × 400-m) at the same relative intensity (ie, critical speed), and 1 coach (age 31 y, 7 y coaching experience) rated their efforts. Swimmers’ sRPE was assessed 30 min after the training session. Coach sRPE was collected before each training session. Internal load was calculated by multiplying sRPE by session duration. Results: When bouts with the same repetition distance and different volumes (10 × 100-m vs 20 × 100-m) are compared, sRPE and internal load are higher in 20 × 100-m bouts. When maintaining constant volume, sRPE and internal load (20 × 100-m, 10 × 200-m, and 5 × 400-m) are higher only in 5 × 400-m bouts. The coach’s and swimmers’ sRPE differed in 10 × 200-m and 5 × 400-m. Conclusions: These results indicate that sRPE in swimming is affected not only by intensity but also by volume and repetition distance. In addition, swimmers’ and the coach’s sRPE were different when longer repetition distances were used during training sessions. Therefore, care should be taken when prescribing swimming sessions with longer volume and/or longer repetition distances. Keywords: swimming, critical speed, interval training The aim of any sports training is to induce morphological, metabolic, and functional changes that cause improvements in athletes’ performance. An optimal training program should offer the appropriate stimuli (ie, training loads) to produce performanceleading adaptations.1,2 A theoretical model suggests that internal training load is responsible for training adaptations.3 In addition, it is thought that internal-training-load variations throughout periods and cycles of periodization play an important role in the success of the training process.4 Consequently, coaches and practitioners deliberately plan these variations in an attempt to induce adaptations and to improve performance. Therefore, monitoring and controlling internal load are of paramount importance to ensure optimal performance enhancement.5,6 Internal load is particularly influenced by external load (ie, training variables) but is difficult to assess.7 In cyclic sports such as swimming, external load is mainly determined by volume (eg, distance), intensity (eg, %V˙O2max), and frequency (number of weekly training sessions) of training, which can be easily controlled. Although external load is the main influencing factor, individual characteristics such as training status and genetic potential may greatly affect internal load.3,8 According to this paradigm, internal load results from the interaction of external load and individual characteristics. Thus, it is conceivable that the same external load, even when exercise intensity is controlled, does not induce the same physiological stress (internal load) in different athletes, thus affecting training adaptations.9 Barroso and Salgueiro are with the Dept of Sport Sciences, State University of Campinas, Campinas, Brazil. do Carmo is with the School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil. Nakamura is with the Multicentric Research Group in Sports Sciences, State University of Londrina, Londrina, Brazil. Address author correspondence to Renato Barroso at [email protected]. 848

In spite of the difficulties in controlling and monitoring internal training load, blood lactate, heart rate, and oxygen uptake (V˙O2) have been suggested for quantifying the magnitude.3,9 Nevertheless, their assessment is not feasible in a “real-world” setup,5,6 especially in swimming, where the environment (ie, water) may cause equipment malfunction. Training impulses (TRIMPs), such as that of Banister or Edwards, have been created to quantify training loads. Unfortunately, these TRIMPs also require heart-rate data to be calculated, which hinders their use. In addition, it is arguable whether these assessments would provide valid measures that are comparable to perceptual assessments.10 Perceptual assessments, which include rating of perceived exertion (RPE), have been successfully used both during and after exercise to assess exercise intensity. For instance, according to the estimation-production paradigm, individuals are able to accurately produce any given intensity assessed in a previous exercise trial when they should estimate their perception of effort.11 The results of studies on this paradigm support the use of in-task (during-exercise) RPE for prescribing, regulating, and assessing exercise intensity.12–14 In an innovative application of the concept of perceived exertion, Foster et al15 used a modified CR-10 Borg scale16 and asked athletes to rate their effort for an entire workout 30 minutes after the end of the exercise, yielding the session RPE (sRPE). This sRPE positively correlates to the average percentage heart-rate reserve15 and replaces heart rate as a marker of intensity in the Banister17 TRIMP concept. Notably, even though sRPE has been considered a marker of training intensity, there is evidence that it may be sensitive to other external-training-load-determining factors such as the volume of continuous and stochastic exercise and the repetition duration/ distance during interval training.2,18–20 Even though the influence of these variables is considered minor, these results were obtained from stochastic and continuous training in dry-land exercises. In addition, it is important to point out that interval training is the most common method used during swimming training.21 Thus, it

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is essential to understand whether volume and repetition distance during interval training influence swimmers’ perception of effort and internal training load. Wallace et al22 and Barroso et al23 reported that swimmers’ and coaches’ sRPE differed in several training bouts, which implies that external training loads prescribed by the coaches may not induce the desired adaptations in all swimmers. Although those authors did not mention the training sessions performed, it is possible that variables associated with external load affect how swimmers perceive training stimuli and thus affect the coaches’ and swimmers’ sRPE relationship. Thus, the objective of this study was to assess sRPE after standardized sets of interval training performed at the same relative intensity in swimmers, except with different total volume and repetition distance. These sets were designed to allow a comparison of training volume and repetition distance. We hypothesized that both volume and repetition distance would affect sRPE in moderately trained swimmers.

Methods

a typical training session for these swimmers. In addition, the sets allowed us to investigate the effects of training volume (10 × 100-m vs 20 × 100-m) and repetition distance (20 × 100-m, 10 × 200-m and 5 × 400-m) on sRPE. All repetitions were performed at the intensity corresponding to individually determined CS. The rest interval between repetitions was individually set to allow a 4:1 effort:rest relationship, which is close to that recommended by Maglischo25 when using this intensity.

Statistical Analysis Data are expressed as mean ± SD; normality was ensured through standard visual inspection and a normality test (Shapiro-Wilk). To compare the effects of volume on sRPE, a paired Student t test was performed comparing 10 × 100-m with 20 × 100-m. Mixed-model analysis, assuming set (20 × 100-m, 10 × 200-m, or 5 × 400-m) as a fixed factor and subjects as a random factor, was used to compare repetition distance. A Tukey post hoc adjustment was used in case of significant F values. To compare swimmers’ and the coach’s sRPE we used the 1-sample t test, assuming the coach’s sRPE as the hypothesis mean. Significance level was set at P < .05.

Sample Thirteen moderately trained male swimmers (21.1 ± 1.1 y, 178 ± 6 cm, 74.1 ± 8.3 kg, 100-m freestyle 60.2 ± 2.9 s) and 1 coach (age 31 y, 7 y coaching experience) participated in this study. All swimmers competed regularly in local championships in 50-m and 100-m in all strokes (n = 8) and 100-m in all strokes and 200-m individual medley (n = 3). This study was approved by the university’s ethics committee; participants were informed of the objectives, possible risks, and benefits of the study; and before participation they provided written informed consent.

Experimental Procedures Participants were familiarized with the CR-10 Borg RPE scale2 as this was part of their training routine. The RPE (ie, load intensity) was determined through the sRPE method. This method uses a simple question: “How was your training session today?” The answer was provided 30 minutes after the end of the session by choosing a descriptor and a number from 0 to 10, which could also be provided in decimals (eg, 7.5). Internal load was calculated by the multiplication of sRPE by the duration of the training session in minutes. Concerning the coach, the planned load-intensity classification was rated before the beginning of each training session. Swimmers were evaluated on 6 nonconsecutive days. During the first and the second days, swimmers were asked to perform either a 200-m or a 400-m repetition aiming at their best result. Times for each distance were plotted and a regression line was drawn for each swimmer. Critical speed (CS) was then calculated as the angular coefficient (ie, slope) of the regression line between distance and time of these 2 distances.24 CS was then used during experimental sessions. Experimental training sessions took place in a heated pool (26–28°C) and were performed as part of the specific conditioning phase, in a randomized order 48 hours apart. Between-sessions intervals consisted of light-intensity training sessions. During the experimental session, swimmers performed a standardized warm-up. Ten minutes after the warm-up, they performed 1 of the standardized sets. Four standardized sets were designed: 10 × 100-m, 20 × 100-m, 10 × 200-m, and 5 × 400-m. We chose these sets as they represented

Results Swimmers’ average performances in 200-m, 400-m, and CS were 149.6 ± 8.6 s, 329.6 ± 17.7 s, and 1.11 ± 0.07 m/s, respectively. Figure 1 illustrates sRPE means and individual values for 10 × 100-m and 20 × 100-m bouts, where it is possible to observe the effects of training volume, keeping all other variables (intensity and repetition distance) constant. The coach rated sRPE for 10 × 100-m as 3 and for 20 × 100-m as 4, and these values were not different from those of the swimmers (P = .57 and P = .28 for 10 × 100-m and 20 × 100-m, respectively). Figure 2 presents means and individual values of sRPE for 20 × 100-m, 10 × 200-m, and 5 × 400-m bouts. It can be observed that, keeping volume and intensity constant, the 400-m bout induced higher sRPE values than 200-m (P = .002) and 100-m (P = .029) bouts. Notably, there was no difference between 100-m and 200-m bouts. The coach’s sRPE for the 20 × 100-m, 10 × 200-m, and 5 × 400-m were 4, 5, and 6, respectively. Coach and swimmer sRPE differed for 10 × 200-m (P = .005) and 5 × 400-m (P = .033). Regarding training volume, the coefficient of variation (CV) of sRPE increased from 16.9% to 19.2% in the 10 × 100-m and 20 × 100-m, respectively. The CV was even higher in the 10 × 200-m (21.6%) and 5 × 400-m (27.2%).

Discussion The aim of this study was to compare sRPE values and internal load for training bouts with different volumes and repetition distances and durations. The main findings of this study are that both training volume and repetition distance affect sRPE and internal load in moderately trained swimmers. Even though sRPE has been considered a marker of training intensity, the possible influence of training volume on sRPE can be observed in Foster et al.2 From their results, it is possible to calculate sRPE in 30-minute and 90-minute bouts at the same intensity, with sRPE for 90 minutes being ~10% higher than for 30 minutes (4.8 vs 4.3, respectively). Similar results were obtained by Haddad et al20 and Green et al,19 who reported a minor influence of volume on sRPE in tae kwon do athletes and physically active subjects,

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Figure 1 — Session rating of perceived exertion (SRPE) and internal load (a.u.) for 10 × 100-m and 20 × 100-m. Open circles and dashed lines represent individual values. Filled circles and continuous line represent mean ± SD. Abbreviations: a.u., arbitrary units. *P < .05 between bouts.

Figure 2 — Session rating of perceived exertion (sRPE, arbitrary units, a.u.) and internal load (a.u.) for 20 × 100-m, 10 × 200-m, and 5 × 400-m. Open circles and dashed lines represent individual values. Filled circles and continuous line represent mean ± SD. Abbreviations: a.u., arbitrary units. *P < .05: 5 × 400-m greater than 20 × 100-m and 10 × 200-m.

respectively. Although these results were obtained from stochastic and continuous exercises, interval training is the most common method used during swimming training.21 Thus, it is important to know how volume during interval training affects swimmers’ perception of effort and internal training load. The results of this study demonstrate that interval-training volume affects sRPE and internal training load. The influence of greater volume on internal load is expected, since internal load is calculated by the multiplication of a marker of intensity (ie, sRPE) by the volume (ie, duration in minutes). Nevertheless, as sRPE is also affected by training volume, the latter has been taken into account twice, overestimating the importance of training volume on internal training load. Therefore, caution should be taken when prescribing longer training volumes. Notably, repetition distance also affects sRPE. During continuous exercise with constant intensity, in-task RPE has been shown to rise linearly.12,18,26,27 The sRPE, on the other hand, is supposed to reflect the overall intensity of the training session. It should, then, not be affected by modifying set distance while maintaining constant intensity, as in the current study. However, increasing repetition distance from 100 m to 400 m induced an increase in sRPE without any change in training intensity. In addition, internal training load was higher in the 5 × 400-m training session. This result is contrary to those reported by Foster et al2 during cycling exercise. Those authors did not observe any difference in training load when vol-

unteers performed 30/30-second, 60/60-second, or 120/120-second interval training for 30 minutes at the same relative intensity. We did not assess heart rate, V˙O2, or blood lactate to have a physiological variable. These variables are not easy to measure during a swimming session. However, Bentley et al28 assessed these variables during 2 different sets (4 × 400-m and 16 × 100-m) in elite swimmers, which were similar to those used in this study. Even though intensity was a little higher than that in the current study, V˙O2, time spent near V˙O2max, blood lactate, and heart rate were not different between sets, suggesting that these variables would be similar in the current study. It is possible that this response is sport-dependent, related to the environment where the exercise is performed. During swimming, drag created by the swimmer’s body (ie, passive drag), and movement (ie, active drag) is an important factor that hinders displacement. In-task RPE rises during the exercise, reflecting a greater effort during longer repetition distances. Thus, fatigue may develop and impair swimmers’ body positioning.25 A poor body position increases drag and, consequently, effort to maintain the same swimming speed throughout the distance,29 ultimately affecting sRPE. Alternatively, it is possible to suggest that the findings of this study are dependent on swimmers’ training status. Garcin et al27 observed that moderately trained athletes rated exercise at similar relative intensities as more strenuous than did highly trained athletes.

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Seiler and Kjerland30 reported that training near the second ventilatory threshold, similar to the intensity obtained with the CS, is supposed to yield an sRPE close to 7. We are surprised by the large variation of sRPE responses to the interval training prescribed using the individual CS, especially since Wakayoshi et al31 demonstrated a close agreement between CS derived from 200-m and 400-m trials and the maximal lactate steady state in swimmers. sRPE ranged from less than first-ventilatory-threshold values (ie, ≤4) to second ventilatory threshold (ie, ≥7) in our sample, taking as reference the values reported by Seiler and Kjerland.30 Therefore, future studies should clarify the cause of the large variability in sRPE in response to the same physiological intensity in swimmers. Alternatively, it is possible that, even though CS is a wellrecognized and -studied method to prescribe training intensities,32 it overestimated the swimming speed at which anaerobic threshold was achieved in some swimmers. If this is true, swimmers were not swimming in steady state and V˙O2 was still increasing (ie, slow component), eventually reaching V˙O2max if the exercise was of sufficient duration. Thus, it is possible that in the longer-distance set (ie, 5 × 400-m), swimmers attained V˙O2max,33 thus elevating sRPE. The same did not happen in shorter-distance sets (ie, 20 × 100-m and 10 × 200-m), as swimmers’ V˙O2 did not reach maximal values (along with ventilation) and sRPE was not affected. This result highlights the importance of correctly prescribing intensities,9 especially those near anaerobic threshold (ie, CS). In addition, this fact may have contributed to the increase in the CV of sRPE and internal load observed with higher volume and longer distances. The higher CV means that athletes’ perceptions of effort are more variable and may represent a challenge for coaches to precisely prescribe internal training loads for all athletes on the same team. Unexpectedly, the sRPE expressed by the coach was also affected by volume and repetition distance, indicating that swimming coaches may already take into account the influence of volume and repetition distance observed in this study. However, the coach overestimated sRPE (compared with swimmers) in longer repetition distances (ie, 200 m and 400 m). The validity and feasibility of prescribing training based on the expected RPE (production mode) to reduce the between-subjects variation in the training loads and hence induce the desired training adaptations remains to be established. It is important to highlight that only 1 coach rated the training sessions, and this result may not be reproduced with other coaches.

Practical Application Increasing volume by adding repetitions and/or the distance per repetition seems to be related to amplified interindividual sRPE variability (ie, CV). This fact may hamper internal-load control, even if external load is the same and based on individual CS. Thus, alternative methods for prescribing training to a group of athletes aiming at the same internal load might be more appropriate, such as those based on the estimation-production paradigm. This suggestion should be investigated and could alter how interval endurance training is prescribed.

Conclusion Greater volume and repetition distance during interval training influences session rating of perceived exertion (sRPE), increases interindividual variability, and may affect coaches’ and swimmers’ sRPE relationship.

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