The Ratio HLa: RPE as a Tool to Appreciate ...

The Ratio HLa : RPE as a Tool to Appreciate Overreaching in Young High-Level Middle-Distance Runners Physiology and Biochemistry 16

Abstract The purpose of the present investigation was to study the effects of eight weeks of intensive training at the beginning of the athletic season on perceived exertion and on the ratio of blood lactate concentration to ratings of perceived exertion (HLa : RPE) in young runners. Eight high-level middle-distance runners performed two exhausting exercises on an indoor track before and after eight weeks of training. The first test was an incremental exercise to determine their maximal oxygen uptake (V˙O2 max), the velocity associated with V˙O2 max (vV˙O2 max), the velocity of the lactate concentration threshold (vLT) and the velocity delta 50 (vD50 : the velocity halfway between vV˙O2 max and vLT). The second test was a constant-load all-out run at vD50 to determine the time to exhaustion at this intensity (tlim vD50). There were five training sessions a week with interval training twice a week. After eight weeks of training, vV˙O2 max, vLT and tlim vD50

Introduction

were not significantly different. The athletes perceived exercise as being harder after training than before at a same given relative velocity in the incremental test. During the all-out run at vD50, they felt that, at the same given relative time, they could endure less after than before training. Moreover, the HLa : RPE ratio was significantly lower after intensive interval-training performed immediately after the holidays. Consequently, two intervaltraining sessions per week would induce an overreaching state that is not yet characterized by a decrease in performance and physiological values whereas perceived exertion (RPE, ETL) and especially the HLa : RPE ratio allows the detection of changes in young high-level middle-distance runners. Key words Perceived exertion · exhaustion time · middle distance running · overreaching

haustion time (Estimated Time Limit, ETL) has also been used in addition to RPE during exercise, to further understand how the subject is feeling [15]. Whereas slight changes in the feelings of athletes while exercising could have substantial effects upon their performance, it seems interesting to focus on athletes’ feelings during exercise in order to appraise and check training effects. Some studies have already dealt with the effects of endurance training on perceived exertion [10,12,13,16, 27, 31]. However, no longitudinal

Institution 1 Laboratoire d’Etudes de la Motricit= Humaine, Facult= des Sciences du Sport et de l’Education Physique, Universit= de Lille 2, Ronchin, France 2 Centre de M=decine du Sport C.C.A.S., Paris, France Corresponding Author M. Garcin · Laboratoire d’Etudes de la Motricit= Humaine · Facult= des Sciences du Sport et de l’Education Physique · Universit= de Lille 2 · 9 rue de l’Universit= · 59790 Ronchin · France · Phone: +33 (320) 88 73 69 · E-Mail: [email protected] Accepted after revision: May 9, 2001 Bibliography Int J Sports Med 2002; 23: 16–21 G Georg Thieme Verlag Stuttgart · New York · ISSN 0172-4622

Int J Sports Med 1/2002 20.12.2001 blackcyanmagentayellow

Physiological parameters are often used to appraise training effects, whereas athletes feelings during exercise are overlooked. Nevertheless, numerous studies have shown that the use of the Rating Scale of Perceived Exertion (RPE, from 6 – 20), described by G.V. Borg in 1970, was a good indicator of physical stress and physical working capacity [2, 8,14]. This scale is used for clinical, ergonomic, pedagogical and sporting applications [25]. A second perceived exertion scale based on subjective estimation of ex-

M. Garcin1 A. Fleury1 V. Billat1,2

study has focused on the effects of interval training performed on the track at the beginning of the athletic season for young high-level runners on perceived exertion. Indeed, most studies dealing with healthy young adults were on sedentary or active young men or women and did not approach training [1,14, 23, 24].

Therefore, the purpose of the present investigation was to study the effects of eight weeks of interval training at the beginning of the athletic season on perceived exertion and on the ratio of blood lactate concentration to ratings of perceived exertion in young high-level middle-distance runners.

The criteria used for V˙O2 max were a plateau in V˙O2 despite an increase in running speed and heart rate (HR) over 90 % of the predicted maximal heart rate [29]. The velocity associated with V˙O2 max (vV˙O2 max) was the lowest running speed which elicited a V˙O2 value equal to V˙O2 max [5]. The velocity of the lactate concentration threshold (vLT) was determined by the relationship between blood lactate concentrations and velocity and was defined as the velocity for which an increase in lactate concentration correponding to 1 mmol U l–1 occurred between 3 and 5 mmol U l–1 [3]. Velocity delta 50 (vD50) which was the velocity halfway between vV˙O2 max and vLT, was calculated as follows: vD50 = vLT + ([vV˙O2 max–vLT]/2).

Method Subjects Eight high-level endurance-trained males (20.1 M 4.0 years, 62.5 M 5.1 kg, 176.0 M 5.1 cm) participated in the study at the beginning of the athletic season (October – December). The subjects were medically examined before they signed an informed consent form about the purpose and procedures of the experiment.

Materials

Two days later and on the same track the athletes performed a constant-load exercise up to exhaustion at vD50 to determine the time to exhaustion at this intensity (tlim vD50). Each subject was verbally encouraged to continue for as long as possible. For eight weeks, the runners completed five training sessions each week (two interval training and three continuous training sessions). Intermittent exercise training stimulus was standardized by alternating four repetitions of periods equal to 50 % of tlim vD50 at velocity vD50 with half durations of recovery at 50 % of vV˙O2 max (i. e. periods of recovery equal to 25 % of tlim vD50) (work : rest = 1 : 1/2) [11]. Continuous exercise training stimulus was 1 hour running at 65 – 75 % vV˙O2 max.

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Thereafter, in a second session on the same track they performed the same exhausting exercises at the same time of day. Before and after training, speed was checked during the incremental and the constant exercises by the experimenters. On the track, the runners followed a pacing cyclist travelling at the required velocity. The cyclist received audio cues via a Walkman (SonyN), the cue rhythm determining the speed needed to cover 25 m. Visual marks were set at 25-m intervals along the track (inside the first lane) [6]. Moreover, experimenters independently measured the time required to complete 25 m in order to check the pacer and runner speed. For the incremental and the constant-load exercises, exhaustion was defined when the subject was unable to sustain the velocity, i. e., when the runner was more than 5 m behind the cyclist. During the exercise, heart rate and oxygen uptake were averaged every 15 seconds. Fingertip blood samples were taken at the end of every stage (during the 30-seconds rest) during the incremental exercise and at the end of the constant-load all-out run. The scales were explained before each exercise. These scales were written on a board fixed on the back of the experimenter


M. Garcin et al., The Ratio HLa : RPE as … Int J Sports Med 2002; 23: 16 – 21

Heart rate (HR) and oxygen uptake (V˙O2) were measured with a telemetric system (CosmedN K4b2, Italy). This material has been validated by Hausswirth et al. [17]. Heartbeats and expired gases were collected and transmitted to the K4b2 receiving unit. Before each exercise, the O2 analysis system was calibrated using ambient air, which was assumed to contain 20.9 % of O2 (K4b2 instructions manual). The calibration of the turbine flowmeter of the K4b2 was performed using a 3 – 1 syringe (Quinton InstrumentsN, Seattle). Fingertip capillary blood samples were collected in a capillary tube and were analyzed for lactate concentration using a Dr LangeN, LP20 (Berlin, Germany). Blood lactate concentration was determined by enzymatic oxidation analysis. The perception of exertion was expressed according to two scales: a French translation [26] of the Rating scale of Perceived Exertion (RPE) [7] which consisted of 15 assessments between 6 and 20 (from “very very light” to “very very hard”), and a second scale based on subjective Estimation of Time Limit (ETL) [15] which consisted of 20 assessments between 1 and 20 (from “more than 16 hours” to “2 minutes”). This scale was designed as a function of the logarithm of the estimated exhaustion time (tlim) (ETL = a-b log [tlim]).

Physiology and Biochemistry

Snyder et al. [28] used perceived exertion (CR-10 scale) combined with blood lactate concentration (HLa) in order to detect over-reached status in male adult competitive cyclists. The authors showed that the ratio of blood lactate concentration to ratings of perceived exertion (HLa:RPE ratio multiplied by 100) decreased for all workloads following two weeks of intensive interval-training. The major reason for the decline in the HLa:RPE ratio during the overtraining period was a reduction in lactate concentration, as RPE did not change.

Experimental design In a first session, the subjects performed an incremental exhausting exercise on an indoor track (200 m) to determine their maximal oxygen uptake (V˙O2 max). According to the performances of these athletes, the initial speed was set at 14 km U h–1 and increased by 1 km U h–1 every 3 minutes until 17 km U h–1 was attained. Each stage was separated by a 30-seconds rest. Then, after a 90 seconds rest, each incremental stage lasted 2 minutes and the speed was increased by 1 km U h–1 until exhaustion, without resting time. Each subject was verbally encouraged to give maximum effort.

Table 1

˙O2 max, vD50 and vLT, before and after eight weeks of Physiological and psychological means (M) and standard deviations (SD) at vV training (n = 8) V˙O2

velocity

Physiology and Biochemistry 18

HR

BLC

(km h–1) before after

(ml min–1 kg–1) before after

(bpm) before after

(mmole l–1) before after

RPE

ETL

before

after

before

after 17.0

at ˙O2 max vV

M

20.6

20.6

64.8

64.2

191

192

12.1

11.1

17.1

17.6

16.1

SD

1.0

0.8

3.6

3.8

8

6

3.1

2.9

1.4

1.2

3.2

at

M

19.5

19.8

62.7

63.1

186

188

7.6

7.2

15.2

16.8

13.3

vD50

SD

1.0

0.8

3.5

3.1

5

5

2.8

1.8

1.7

0.9

2.9

at

M

18.2

18.4

58.4

58.3

181

182

4.1

4.2

13.9

14.8

11.3

vLT

SD

1.2

1.0

3.0

3.2

4

4

0.6

0.9

1.9

1.3

2.1

2

1.9 2

15.4 1.8

2

12.6 1.5

˙O2: oxygen uptake. HR: heart rate. BLC: blood lactate concentration. RPE: Rating scale of Perceived Exertion. ETL: Estimated Time Limit. vV ˙O2 max: velocity associated V ˙O2 max and vLT. vLT: velocity of the lactate concentration threshold. 2significantly p < 0.05. ˙O2 max). vD50: velocity halfway between vV with maximal oxygen uptake (V

who rode in front of the subject. The subjects were asked “How hard do you feel this exercise is ?” and “How long would you be able to perform an exercise at this intensity to exhaustion?” During the incremental exercise, subjects had to give ratings corresponding to their sensations during the end of each stage. Up to 17 km U h–1, the subjects had to point to a value on the perceived exertion scales and the ratings were collected during the 30-seconds rest. Thereafter, subjects expressed the perceived exertion values with their fist (= 10 points) or fingers (each = 1 point) at the end of each step, i. e., during the last 15 seconds of each 2 minutes stage to a second experimenter who rode next to the runner and collected the values. The procedure was the same for the constant-load exercises but perceived exertion values were recorded every 2 minutes up to the end of exercise. The order of RPE and ETL was the same during the four exercises for each subject, but was randomized among the subjects.

We checked that before and after training, perceived exertion and estimated time limit were significantly correlated with V˙O2, HR or velocity expressed in percentage of vV˙O2max (% vV˙O2max) (p < 0.01; Fig. 1). However, training induced a significant upward shift of the %vV˙O2 max-RPE regression shown by the covariance analysis (F[1,123] = 7.05) (p < 0.01) (Fig. 1). This means that for a same given relative velocity (% vV˙O2 max), athletes perceived exercise as harder after training than before. Concerning the estimated time limit, there was the same upward shift of the %vV˙O2 max-ETL regressions after training, however, the result of the covariance analysis was not statistically significant (F[1,123] = 3.64). The results were similar for heart rate - perceived exertion or estimated time limit, and perceived exertion – estimated time limit relationships. Indeed, the relationship between RPE and ETL before and after training was not significantly different in the incremental test (F[1,123] = 1.08) (Fig. 2). This means that estimated time limit remained the same after training as before for a given perceived exertion value.

Results V˙O2 max, maximal heart rate (HR max) and running economy at the same absolute speed, i. e., 14 km U h–1 did not change after eight weeks of interval training (66.2 M 3.8 ml U min–1 U kg–1 vs. 66.3 M 2.1 ml U min–1 U kg–1, 192 M 7 bpm vs 193 M 6 bpm, and 45.8 M 3.1 ml U min–1 U kg–1 vs. 45.5 M 1.6 ml U min–1 U kg–1, respectively). The lactate threshold was 88.2 M 3.4 % V˙O2max before training vs 88.1 M 4.0 % V˙O2max after training and physiological averages at vV˙O2 max, vD50 or vLT were not significantly different after training (Table 1). vD50 elicited 94.8 M 1.8 % vV˙O2max

Fig. 1 Relationships between perceived exertion (RPE) and velocity ˙O2 max) during the incremental ex(expressed in percentage of vV hausting exercise before training (black dots and thick regression line, r = 0.85) and after training (empty circles and dashed regression line, r = 0.91) (n = 8).


For a given relative time (%tlim), physiological responses but V˙O2 were not significantly different after training. Indeed, the upward shift of the %tlim-V˙O2 regression with training was signifi-


Statistical analysis Results are presented as mean (M) M standard deviation (SD) values. The Kolmogorov-Smirnov test (with Lilliefor’s correction) was used to test data for normality (Sigma StatN, Jandel, Germany). Statistical differences between pre- and post-training means for the different parameters (velocity, V˙O2, HR, RPE or ETL) at a given velocity (vV˙O2 max, vD50 or vSL) were tested with a Student’s t-test for paired data (with parametic data) or a Wilcoxon test (with nonparametic data) (Sigma StatN, Jandel, Germany). The relationships between pairs of variables were analyzed by a Pearson product moment test (Sigma StatN, Jandel, Germany). A covariance analysis [18] was carried out for the relationships between parameters in order to estimate the effect of training on perceived exertion for a given parameter.

before training vs 95.8 M 1.8 % vV˙O2 max after training. Tlim vD50 was not significantly different after compared to before training (325 M 104 seconds vs. 335 M 85 seconds, respectively).

Fig. 4 Relationships between perceived exertion (RPE) and the estimated time limit (ETL) during the constant-load exhausting exercise before training (black dots and thick regression line, r = 0.82) and after training (empty circles and dashed regression line, r = 0.55) (n = 8).

Fig. 5 Relationships between the ratio of blood lactate concentration to ratings of perceived exertion (HLa : RPE ratio) and velocity during the incremental exhausting exercise before training (black dots and thick regression line, r = 0.71) and after training (empty circles and dashed regression line, r = 0.60) (n = 8).

Fig. 3 (a) Relationships between perceived exertion (RPE) and time (expressed in percentage of exhaustion time) during the constantload exhausting exercise before training (black dots and thick regression line, r = 0.54) and after training (empty circles and dashed regression line, r = 0.56) (n = 8); (b) Relationships between the estimated time limit (ETL) and time (expressed in percentage of exhaustion time) during the constant-load exhausting exercise before training (black dots and thick regression line, r = 0.61) and after training (empty circles and dashed regression line, r = 0.63) (n = 8).

cant (F[1,46] = 11.93) (p < 0.01). Hence, at given relative time (%tlim), V˙O2 was higher after training. RPE and ETL were significantly correlated with time expressed in percentage of exhaustion time (%tlim) (p < 0.01; Fig. 3 a,b). This means that athletes perceived exercise as being harder and felt that they could endure this velocity less with exercise duration. The upward shift of the %tlim-ETL regressions with training was significant

In the incremental test, submaximal and maximal lactate concentrations decreased with training but not significantly (p = 0.15 and p = 0.48, respectively), whereas RPE increased significantly with training (p < 0.01). Consequently, HLa : RPE ratio was significantly lower after training (p < 0.01) (Fig. 5). Examination of individual responses revealed that, of the eight athletes studied, five subjects showed a decrease in the HLa : RPE ratio after training. In constant-load test, maximal lactate concentrations, RPE values and HLa : RPE ratio at the end of exercise did not significantly decrease after intensive training (13.61 M 3.44 mmol U l–1 vs 13.46 M 4.07 mmol U l–1, 18.25 M 1.75 vs 18.00 M 1.20, and 74.16 M 15.37 vs 72.44 M 20.23, respectively) (p = 0.91, p = 0.71 and p = 0.81, respectively).

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(F[1,46] = 11.32) (p < 0.01; Fig. 3 b)., i. e., at the same given relative time (%tlim), athletes felt that they could endure less after training than before at 95 % vV˙O2max. Concerning perceived exertion, there was the same upward shift of the %tlim-RPE regressions after training, however, the result of the covariance analysis was not statistically significant (F[1,46] = 1.77). In the end, the upward shift of the RPE-ETL regression with training in constantload test was significant (F[1,46] = 7.75) (p < 0.01) (Fig. 4), i. e., for a same given perceived exertion, athletes felt that they could endure less after training.


Fig. 2 Relationships between perceived exertion (RPE) and the estimated time limit (ETL) during the incremental exhausting exercise before training (black dots and thick regression line, r = 0.81) and after training (empty circles and dashed regression line, r = 0.87) (n = 8).

Discussion The main results of this study were that 8 weeks of intensive training performed immediately after the holidays including two weekly sessions of interval training at 95 % vV˙O2max added to three weekly sessions of continuous training (65 – 75 % vV˙O2max) did not induce an additional improvement of aerobic capacity (V˙O2max, vV˙O2max, vLT, vD50, tlim vD50). Moreover, intensive interval training increased perceived exertion values and decreased HLa : RPE ratio. This could mean that a possible overreaching was induced by intensive interval training performed immediately after the holidays.

Physiology and Biochemistry 20

Our results are similar to those of Billat et al. [4] who did not find any improvement in V˙O2max or vV˙O2max after three intervaltraining sessions (five repetitions of periods equal to 50 % of tlim vV˙O2max at velocity vV˙O2max with the same durations of recovery at 60 % of vV˙O2 max) and three continuous training sessions (two sessions at 60 – 70 % vV˙O2max and one session at the onset of blood lactate accumulation velocity) per week. The great mean variation of RPE or ETL for a given %tlim (Figs. 3a, b) can be explained by both the lower values of tlim vD50 and by the fact that RPE and ETL values were collected every 2 minutes. Indeed, some subjects with a lower time limit rated higher values (RPE or ETL = 19 or 20) before the end of the constant-load exercise. For example, one subject with tlim vD50 = 325 seconds, rated RPE = 19 at 2 minutes. This value corresponded to 37 % tlim.

Despite a calibration of interval training with individual time to exhaustion at vD50, it seems that eight weeks of training including two weekly sessions of interval training was too intense just after the holidays and one session of interval training might be sufficient [4]. Moreover, it is very interesting to observe that the RPE-ETL relationship was very similar during incremental exercise after training. It implies that there was a close relationship between hardness and exhaustion time during an incremental exercise, whatever the results of a training program. Therefore, perceived exertion scales seem to be an important complementary tool to physiological parameters in order to estimate the effects of a training program during exhausting exercises. This subjective approach has the advantage of not being invasive in the detection of a state of overtraining [4].


After eight weeks of training our subjects estimated the exercise intensity as being harder during an incremental exhausting exercise and thought they would be able to maintain the exercise intensity for a shorter time during a constant exhausting exercise. Thus we may suggest that either these athletes lost their rating ability at the beginning of the athletic season and were optimistic, or these results were the beginning of an overreaching state due to eight weeks of interval training without a holiday. As our subjects were high-level athletes, they were well aware of their capacities, and probably became overreached during this period. Indeed, the increase in perceived exertion values during exercise may suggest that this training could have compromised the recovery to the point of inducing an overtraining syndrome.

As each exercise was carried out only once before and after the training period, dependence of subjective tests on daily individual performance may be considerable. Consequently, physiological data such as HLa may contribute to attest the results obtained from the psychological data. The combined result would appear in the HLa : RPE ratio. Snyder et al. [28] and Jeukendrup et al. [21] found similar RPE values in competitive cyclists after two weeks of normal training followed by two weeks of intensive interval-training, whereas they showed a decrease in lactacte concentration values after training. Consequently, they observed a decline in the HLa : RPE ratio during the overtraining period. All seven athletes were classified as overreached after these four weeks of training. Bosquet et al. [9] found similar results on endurance athletes after four weeks of high volume training (continuous slow running was increased by 100 % within 4 weeks). Seven athletes were classified as overreached and three as overtrained after these four weeks of training. However, the decline in the HLa : RPE ratio could also be explained by a decrease in maximal lactate concentration during an incremental test whereas RPE increased during the test after an overtraining period [30]. Similarly, the decline in the HLa : RPE ratio observed in our study (Fig. 5) is explained by unchanged submaximal and maximal lactate concentrations, whereas RPE increased significantly after intensive training. As some subjects presented a significant increase in RPE, whereas the ratio did not change, we may suggest that some subjects are likely to be overreached when the ratio decreases significantly. Consequently, the use of a ratio of blood lactate concentration to ratings of perceived exertion may confirm the hypothesis suggesting higher RPE or ETL values during exhausting exercise. Therefore HLa : RPE ratio would be useful to appreciate the effects of training programs in detecting the occurrence of short-term overtraining (overreaching).


Despite any statistical performance and physiological difference after training, the results of the present study demonstrated that there was an effect of two interval-training sessions per week on RPE during an incremental exhausting exercise. Indeed, two interval-training sessions per week induced an increase in perceived exertion values for the same relative velocity. Bosquet et al. [9] found similar results but the increase in perceived exertion values was not significant. However, Womack et al. [31] showed that end-exercise RPE values were statistically lower after training despite no improvement of physiological values. These subjects were untrained males. James and Doust [20] observed higher RPE values after intensive training (6 x 800 m intervals at 1 km U h–1 below velocity achieved at V˙O2 max with 3 minutes recovery between each interval), however this result was due to fatigue because these tests were performed 1 hour or 72 hours after the interval-training session.

In effect, this overtraining syndrome is often caused by daily high-intensity interval training with little recovery between repetitions [22]. This increase in perceived exertion values was probably the premise symptom of an overreaching state i. e., a state which is not always characterized by a decrease of performance and physiological values. Since Billat et al. [4] showed that subjective ratings of muscle soreness and quality of sleep according to the Hooper scale increased after interval training, it would be interesting in future research to question subjects about their other perceptions and to use Hooper scales [9,19].

Perceived exertion (RPE and ETL) and especially the HLa : RPE ratio seem to be useful to appreciate the effectiveness of an interval-training program at the beginning of the season for high-level middle-distance runners. Therefore, coaches can introduce it in training of athletes combined with the Hooper scales to check the results of the training program of the athletes.

Acknowledgements The authors gratefully acknowledge the administration of the “Stade Couvert R=gional de Li=vin” (France) in which the field tests were performed.

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