Letters to the Editor
International Journal of Sports Physiology and Performance, 2011, 6, 2-7
© 2011 Human Kinetics, Inc.
Intersubjective Comparisons Are Possible with an Accurate
Use of the Borg CR Scales
To the Editor:
We recently read the interesting commentary of Lambert and Borresen,1 which
discusses the advantages and disadvantages of the various measures of training
load in sports. This commentary addressed an important issue in sport science. As
a further contribution, we would like to clarify some arguments presented in the
commentary, particularly on the determination of the training load using the RPE
and the session-RPE method.
Lambert and Borresen1 reported in the abstract that because the session-RPE
method depends on subjective assessment, the intersubject comparisons may be
inaccurate. We believe it is important to clarify that this should not be the case,
since by choosing Borg’s category ratio scales (CR10 and CR100) for subjective
assessment such systematic variance is minimized in agreement with modern
psychophysical theory. Indeed, these scales are level-anchored, semi-ratio scales
that combine the advantages of a ratio scale with those of a labeled category scale
according to the Borg’s range model.2-5 This model asserts that the subjective range
of intensity (from minimal to maximal) is equal between individuals, and evidence
accumulated during the last 40 y has provided support to this theory.3-7 This is why
the Borg scales are valid for prescribing and evaluating exercise intensity in both
the clinical and sport setting. Failure in intersubject comparisons usually arises
from using of scales that (1) have not been developed following the appropriate
psychophysical procedures (ie, not valid) and (2) have been modified so that the
original properties of the scale are lost or changed (eg, self-translation, modification of the numbers and anchors, and similar), or by (3) correlating the perceived
exertion with exercise intensity indicators under different contexts (eg, indicators
not ranging from minimum to maximum, such as the percentage of anaerobic
threshold8). Another crucial point for intersubject comparisons is the use of the
correct instructions and administration procedures, including a valid interindividual
reference point (the so-called fixed star).3 Furthermore, the appropriate instructions are also important because the CR scales are general intensity scales and the
instructions define the domains measured.7 This underlines the importance of using
appropriately validated psychophysical instruments that comprise both the scale
and the relative instructions. Accordingly, when using the session-RPE method,
the original CR10 (or CR100) scale should be used.
Another point raised in the commentary requiring further discussion was the
suggestion that the session-RPE method may be not suitable for quantifying training
load in sports such as rugby union and rugby league. However, there is evidence
of convergent validity between session-RPE and other measures of exercise intensity (eg, heart rate and blood lactate concentration) during both rugby union9 and
rugby league,10-12 with results similar to those of other sports. Additionally, it has
also been shown that the match session-RPE is moderately correlated (r = 0.54)
to the number of tackles completed during a game in professional rugby league,13
2
Letters to the Editor 3
suggesting that the global perceived exertion is also affected by tackling. Although
further studies are probably needed, on the basis of these studies we suggest that the
session-RPE method is an acceptable indicator of training load and can be applied
to the rugby codes in the same manner as to other sports.
Finally, we generally agree that gaining consensus and providing evidence-based
practice guidelines can improve scientific practice, but we do not believe a consensus
on training load measures is warranted at this early stage. Rather, more well-designed
studies experimentally investigating the theoretical link between the training load
and training outcomes are still necessary before such a consensus can be made.
Franco M. Impellizzeri
Research Centre for Sport, Mountain and Health
University of Verona
Rovereto, Italy
franco.impellizzeri@gmail.com
Elisabet Borg
Department of Psychology
Stockholm University
Stockholm, Sweden
Aaron J. Coutts
School of Leisure, Sport and Tourism
University of Technology
Australia
References
1. Lambert MI, Borresen J. Measuring training load in sports. Int J Sports Physiol Perform.
2010;5:406–411.
2. Borg E, Borg G. A comparison of AME and CR100 for scaling perceived exertion.
Acta Psychol (Amst). 2002;109:157–175.
3. Borg G, Borg E. A new generation of scaling methods: Level-anchored ratio scaling.
Psychologica. 2001;28:15–45.
4. Borg G. Borg’s Perceived Exertion and Pain Scales. Champaign, Illinois: Human
Kinetics, 1998.
5. Sagal P, Borg G. The Range Principle and the Problem of Other Minds. Brit J Phil Sci.
1993:477–491.
6. Marks LE, Borg G, Ljunggren G. Individual differences in perceived exertion assessed
by two new methods. Percept Psychophys. 1983;34:280–288.
7. Marks LE, Borg G, Westerlund J. Differences in taste perception assessed by magnitude
matching and by category-ratio scaling. Chem Senses. 1992;17:493–506.
8. Robinson DM, Robinson SM, Hume PA, Hopkins WG. Training intensity of elite male
distance runners. Med Sci Sports Exerc. 1991;23:1078–1082.
9. Cunniffe B, Griffiths H, Proctor W, Davies B, Baker JS, Jones KP. Mucosal immunity
and illness incidence in elite Rugby Union players across a season [published online
ahead of print July 7, 2010]. Med Sci Sport Exerc. doi:10.1249/MSS.0b013e3181ef9d6b.
10. Killen NM, Gabbett TJ, Jenkins DG. Training loads and incidence of injury during the
preseason in professional rugby league players. J Strength Cond Res. 2010;24:2079–2084.
11. Coutts AJ, Reaburn PRJ, Murphy AJ, Pine MJ, Impellizzeri FM. Validity of the sessionRPE method for determining training load in team sport athletes. J Sci Med Sport.
2003;6:525.
4 Letters to the Editor
12. Gabbett TJ, Domrow N. Relationships between training load, injury, and fitness in
sub-elite collision sport athletes. J Sports Sci. 2007;25:1507–1519.
13. Coutts AJ, Sirotic AC, Knowles H, Catterick C. Monitoring Training Loads in Professional Rugby League. In: Reilly T, Korkusuz F, editors. Science and Football VI.
London, UK: Routledge, 2008:272–277.
Response
To the Editor:
We appreciate the thoughtful comments about our article.1 We would like to respond
to the comments and clarify some of the points we made in the paper.
We accept the theory behind the Borg category ratio scale and acknowledge
that the subjective range of intensity is equal between individuals, as you have
pointed out. However, in practice the relationship between internal workload and
perception of effort is not perfect, and therefore there will always be some error
around the measurement.2 This does not negate the practical value of using the
10-point scale in a measurement such as the session-RPE, as we have mentioned
in this article,1 and others.3,4
Our assertion that the session-RPE may not be suitable for assessing training
load in collision sports such as rugby union and rugby league is based on the fact
that there are further aspects to the game that are not captured simply by measuring
session-RPE. The physical demands of the game vary considerably depending on
the playing position. For example, the number of tackles a player makes during a
game can vary threefold,5 and considering that the number of tackles is directly
proportional to the plasma creatine kinase activity 24 h later,6 it can be inferred that
muscle damage also varies considerably between players. We would argue that the
relationship between session-RPE and tackles (r = 0.54) is moderate at best and
only explains 29% of the variance. Clearly, there are aspects of the physiological
stress that are not detected by session-RPE alone.
In order to facilitate the progression of research in this area, we suggest that
the methods of quantifying internal workload need to be standardized, given that
the training and match demands of different sports vary considerably. For example,
aspects specific to the game of rugby (session-RPE, tackles, rucks, lineouts, etc)
during practice and matches need to documented. The definition of each aspect
of the game needs to be carefully standardized, just as the definitions for injuries
have been standardized for cricket,7 rugby,8 and football.9 In our opinion, if training loads are expressed in a more standardized way across studies, the training
outcomes will be interpreted with more vigor.
Michael Ian Lambert
MRC/UCT Research Unit for Exercise Science and Sports Medicine
Department of Human Biology
University of Cape Town
Cape Town, South Africa
Jill Borresen
Discovery Vitality
Johannesburg, South Africa
Letters to the Editor 5
References
1. Lambert MI, Borresen J. Measuring training load in sports. Int J Sports Physiol Perform.
2010;5:406–411.
2. Chen MJ, Fan X, Moe ST. Criterion-related validity of the Borg ratings of perceived
exertion scale in healthy individuals: a meta-analysis. J Sports Sci. 2002;20:873–899.
3. Borresen J, Lambert MI. Quantifying training load: a comparison of subjective and
objective methods. Int J Sports Physiol Perform. 2008;3:16–30.
4. Borresen J, Lambert MI. The quantification of training load, the training response and
the effect on performance. Sports Med. 2009;39:779–795.
5. Hendricks S, Lambert M. Tackling in rugby: Coaching strategies for effective technique
and injury prevention. Int J Sport Sci Coaching. 2010;5:117–135.
6. Takarada Y. Evaluation of muscle damage after a rugby match with special reference
to tackle plays. Br J Sports Med. 2003;37:416–419.
7. Orchard JW, Newman D, Stretch R, Frost W, Mansingh A, Leipus A. Methods for injury
surveillance in international cricket. Br J Sports Med. 2005;39:e22.
8. Fuller CW, Molloy MG, Bagate C, Bahr R, Brooks JH, Donson H, et al. Consensus
statement on injury definitions and data collection procedures for studies of injuries in
rugby union. Br J Sports Med. 2007;41:328–331.
9. Fuller CW, Ekstrand J, Junge A, Andersen TE, Bahr R, Dvorak J, et al. Consensus
statement on injury definitions and data collection procedures in studies of football
(soccer) injuries. Br J Sports Med. 2006;40:193–201.
Erroneous Readings from Ingestible Temperature Capsules
Due to Ingestion of Crushed Ice
To the Editor:
Recent studies have consistently shown that the use of cold fluids/slurry in reducing
body core temperature (Tc) prior to exercise can improve endurance performance
and capacity (Lee et al, 2008; Siegel et al, 2010). The recent study by Ihsan et al
(2010) supports these findings by feeding crushed ice to lower Tc, measured using
ingestible temperature capsules, leading to an improvement in a 40-km cycling
time trial.
A key consideration when using ingestible temperature capsules to monitor
Tc as an alternative to conventional modes (rectal, esophageal, etc), especially in
studies involving ingestion of fluids/foods with temperature very different from
normal Tc, is the uncertainty of its location during measurement due to a range of
gastrointestinal transition times among individuals (Byrne and Lim, 2007). The
ingested capsule can either be excreted on trial day or there can be insufficient time
for it to travel to the distal intestines. The latter can confound the Tc data.
In this study by Ishan et al (2010), even when the capsules were ingested 8–10
h prior to trial, the Tc data (Figure 1; Ihsan et al, 2010) were likely to be directly
influenced by the ingested crushed ice. This assumption is based on a reduction of
1.1 ± 0.59°C in Tc (implying that an individual[s] within the group had Tc lower than
35°C) following completion of the cooling phase, which is physiologically impossible with the approximately 550 g of crushed ice consumed (Siegel et al, 2010;
Stanley et al, 2010). If the readings were true, they would have caused a significant
degree of thermal discomfort. The reported mean difference in perceived thermal
sensation was only about 1.5 units with no difference in mean skin temperature
following ingestion of crushed ice. It was previously shown that poor accuracy may
6 Letters to the Editor
result from using ingestible temperature capsules (even when they were ingested 8
to 11 h prior) with drinks at temperatures lower than normal Tc (Lee et al, 2010),
although the degree is subjected to varying gastrointestinal transition time.
With no robust solution to the problem of insufficient transition time for the
capsule to reach the distal end of intestines, we are left with three alternatives: (1)
removal of data when suspected of transient influence from ingestion of fluids/
foods; (2) extension of capsule ingestion time to greater than 12 h prior to experiment (may even be longer for some individuals but will require pilot trial[s] to
ascertain), but bear the risk of excretion of capsule upon testing; (3) insertion of
capsule as a suppository (Adam et al, 1975; Kenefick et al, 2009). The last option
may not be welcomed by some volunteers.
Jason Kai Wei Lee
Military Physiology Laboratory
Defence Medical and Environmental Research Institute
DSO National Laboratories
Republic of Singapore
lkaiwei@dso.org.sg
References
Adams WC, Fox RH, Fry AJ, MacDonald IC. Thermoregulation during marathon running
in cool, moderate, and hot environments. J Appl Physiol. 1975;38:1030–1037.
Byrne C, Lim CL. The ingestible telemetric body core temperature sensor: a review of
validity and exercise applications. Br J Sports Med. 2007; 41:126–133.
Ihsan M, Landers G, Brearley M, Peeling P. Beneficial effects of ice ingestion as a precooling strategy on 40-km cycling time-trial performance. Int J Sports Physiol Perform.
2010;5:40–51.
Kenefick RW, Ely BR, Cheuvront SN, Palombo LJ, Goodman DA, Sawka MN. Prior heat
stress: effect on subsequent 15-min time trial performance in the heat. Med Sci Sports
Exerc. 2009;41:1311–1316.
Lee JK, Shirreffs SM, Maughan RJ. Cold drink ingestion improves exercise endurance
capacity in the heat. Med Sci Sports Exerc. 2008;40:1637–1644.
Lee JK, Teo YS, Goh LF, Lim CL. Effects of drink temperature after exercise: thermoregulatory responses and accuracy of ingestible temperature capsules. Med Sci Sports Exerc.
2010;42:113.
Siegel R, Maté J, Brearley MB, Watson G, Nosaka K, Laursen PB. Ice slurry ingestion
increases core temperature capacity and running time in the heat. Med Sci Sports
Exerc. 2009;42:717–725.
Stanley J, Leveritt M, Peake JM. Thermoregulatory responses to ice-slush beverage ingestion
and exercise in the heat. Eur J Appl Physiol. 2010;110:1163–1173.
Response
To the Editor:
Thank you for the opportunity to respond to the letter written to you regarding JK
Lee’s thoughts on the recently published paper “Beneficial effects of ice ingestion as
a precooling strategy on 40-km cycling time-trial performance” (Ihsan et al, 2010).
The insights provided by this letter are acknowledged as potential confounding
factors to the use of telemetric pills for the measurement of core temperature (Tc)
Letters to the Editor 7
when consuming crushed ice as a precooling strategy. With this in mind, Ishan et al
(2010) chose to use the term gastrointestinal temperature (Tgi) to represent the data
obtained from the pill, as a result of its potential varied location along the gastrointestinal tract. Unfortunately, the investigation by Lee et al (2010) was not published
at the time of data collection or paper submission. Therefore, the use of the telemetric
pill by Ihsan et al (2010), consumed 8 to 10 h prior to exercise, was appropriate and
in accordance with previously published literature (O’Brien et al, 1998).
When considering the comments in the letter that the Tc of the subjects would
have been lower than 35°C following the completion of the cooling, it must be
highlighted that this assumption has been inferred from a figure, and is unfortunately incorrect. The starting temperature of the participants was 37.1°C, and the
postcooling temperature was 36.1°C. Previous research investigating the use of an
ice slushy or cold water ingestion as a precooling strategy have also shown Tc to
fall to around 36°C (36.4°C, Lee et al, 2008; 36.55°C, Siegel et al, 2010). Because
there have been only three published papers regarding ice slushy ingestion on the
Tc response, it is likely that further research is required before we can confidently
conclude that core temperatures in the low 36°C range (ie, 36.0–36.5°C) are not
possible from crushed ice ingestion.
To this end, the authors acknowledge the comments of this Letter to the Editor
as plausible confounding factors related to the temperature changes seen when using
telemetric temperature pills ingested prior to precooling with crushed ice. However,
it is possible that more research is required to confirm the magnitude of temperature
change one can expect to see from such a precooling strategy. Additionally, the key
findings that a performance improvement of 6.5% can be attained when rapidly
cooling the body prior to exercise should not be overshadowed.
Peter Peeling
Western Australian Institute of Sport
Australia
ppeeling@wais.org.au
References
Ihsan M, Landers G, Brearley M, Peeling P. Beneficial effects of ice ingestion as a precooling strategy on 40-km cycling time-trial performance. Int J Sports Physiol Perform.
2010;5:40–51.
Lee JK, Teo YS, Goh LF, Lim CL. Effects of drink temperature after exercise: thermoregulatory responses and accuracy of ingestible temperature capsules. Med Sci Sports Exerc.
2010;42:113.
O’Brien C, Hoyt RW, Buller MJ, Castellani JW, Young AJ. Telemetry pill measurement of
core temperature in humans during active heating and cooling. Med Sci Sports Exerc.
1998;30:468-472.
Lee JK, Shirreffs SM, Maughan RJ. Cold drink ingestion improves exercise endurance
capacity in the heat. Med Sci Sports Exerc. 2008;40:1637–1644.
Siegel R, Maté J, Brearley MB, Watson G, Nosaka K, Laursen PB. Ice slurry ingestion
increases core temperature capacity and running time in the heat. Med Sci Sports
Exerc. 2010;42:717–725.