From the Tropics to Tassie:
Investigations during a hockey tournament

Wood, R.J., Marsden, J.F. Finn, J.P., From the Tropics to Tassie: Investigations during a hockey tournament. Proceedings of the 7th Applied Physiology Conference, Darwin, Australia, Dec 2000.

The aim of this research project was to gain a better understanding of the body’s responses to travel and competition in a cold climate for Northern Territory athletes. This was achieved by traveling with the NT representative female under twenty-one years hockey team to Hobart, Tasmania, to compete in the national titles. The NT players were analyzed, with players from the ACT squad acting as controls for some measures.

The athletes traveled from the mean daily temperature range of 20.0-30.5oC for Darwin during June, to the mean daily temperature range of 4.0-12.2oC for Hobart in July.

It is always difficult to analyze game data as there are many variables to consider, making the interpretation of results difficult. Although there were differences as the tournament progressed, it is hard to know whether this was due to adaptation to the cold, or because the last games of the tournament included to coldest games.

Full Report

Effect of Competing in a Cold Climatefor Heat Acclimatised Female U/21 Hockey Players

REPORT PREPARED by Rob Wood

SUMMARY

The aim of this research project was to gain a better understanding of the body’s responses to travel and competition in a cold climate for Northern Territory athletes. This was achieved by traveling with the NT representative female under twenty-one years hockey team to Hobart, Tasmania, to compete in the national titles. The NT players were analyzed, with players from the ACT squad acting as controls for some measures.

INTRODUCTION

Athletes from the Northern Territory Institute of Sport (NTIS) who travel away to cold or temperate climates for competition and training often complain and report adverse effects of exercising in the cold. As many athletes are required to travel away from the tropical conditions of Darwin and the Northern Territory (NT) to colder climates as part of their athletic careers, a better understanding of the demands and responses of this is required.

Most previous research in this area has used non-heat acclimatised subjects in determining the physiological effects of exercising in cold environments. The thermoregulatory effects that have been shown include increases in respiratory and peripheral heat loss and subsequent changes to body temperature, and decreases in the threshold for sweating. There are also additional cardiopulmonary and metabolic changes while exercising in the cold compared to thermoneutral conditions, with the net result of decreases in VO2max and performance (Doubt, 1991).

The strategies employed by the body for coping with cold are varied, and the interpretation of the research is not clear (Armstrong, 2000). Young (1996) has identified several strategies that the human body employs to adapt to the cold. The process can be either habituation (or desensitization) in which the body changes in how it senses to cold, or an acclimatization to the cold which involves physiological adaptations for the body to better cope with the cold.

The mechanisms and responses of heat acclimatised athletes exercising in the cold has not been fully investigated, and considering the problems encountered by NT athletes traveling to cooler southern states for training and competition, this was an area worthy of study.

The aim of this research project was to gain a better understanding of the body’s responses to competition in a cold climate for heat acclimatised athletes. This research project determined the effect of the cool conditions on temperature regulatory mechanisms, by monitoring body temperature and sweating during games and during a controlled submaximal exercise test, and determined the effect of this on performance and perceptions of the cold. Also determined was whether acclimatization or desensitization occurred to the cool conditions, and if so to what physiological parameters, and under what time frame.

METHODS

This study involved traveling with the NT representative female under twenty-one years hockey team to Hobart, Tasmania, to compete in the 2000 national titles. The athletes traveled from the mean daily temperature range of 20.0-30.5oC for Darwin during June, to the mean daily temperature range of 4.0-12.2oC for Hobart in July. Humidity was also expected to be 20-30% lower in Hobart, and the chance of rain very high.

Subjects

The subjects for this study were female hockey players competing in the Australian under 21 years National Championships conducted in Hobart, Tasmania. The players in the main study group comprised residents of the northern region of Australia, nine from Darwin, NT, and two from Mt Isa, Queensland. A control group comprised three residents from Victoria (playing in the NT team) and nine from the Australian Capital Territory (playing in the ACT team). All players gave informed consent and the study was approved by the Northern Territory University Human Ethics Committee.

Protocol

Pre-tournament

The players completed a questionnaire every morning (see Appendix 6), starting one week prior to the players leaving Darwin, and continuing until one week after returning (a total of four weeks). The questionnaire required them to fill out their morning body weight and heart rate (optional), the number of hours sleep, and they also had to rate the quality of sleep, muscle soreness and general health levels.

During the two weeks prior to departure, game analysis was performed during a practice game in Darwin on the northern region players only. They also performed a Multistage Fitness Test for determination of aerobic fitness level and maximum heart rate.

Both the Northern Region players and the ACT players performed a submaximal exercise test conducted in controlled conditions in the Sport Science laboratory at either the NTIS or ACT Academy of Sport.

In Hobart

During three tournament games (on days 4, 8 & 14, or days 3, 7 & 13 in Hobart), game physiological parameters were measured on nine players. The nine players to be monitored were split between the two groups of testing days.

During rest days (10, 14, and 20 July), physiological responses were measured using the submaximal exercise protocol, performed in ambient external conditions. These days correspond to days 2, 6, & 12 in Hobart.

Post-tournament

In the week following returning to Darwin or the ACT, the submaximal exercise test was repeated

Data Collection Methods

Step-Test

The physiological responses to exercise in the cold was monitored using a sub-maximal stepping test (for proforma see Appendix 1). A modified Harvard Step Test (Brouha et al., 1943) was performed, using a 50cm step and a stepping rate of 20 steps per minute, for a total time of five minutes.

Heart rate was recorded throughout each test using a heart rate monitor (Polar Vantage NV, Finland). Blood lactate was measured from capillary blood taken from the fingertip using a portable blood lactate analyzer (Accusport, Boehringer Mannheim). Lactate measurements were taken prior to exercise and at one minute post-exercise. Skin temperatures were recorded from thermistors placed on the midpoint anterior surface of the forearm, the midpoint of the posterior surface of the leg, and on the chest on the skin overlaying the manubrium. Skin temperature measurements were taken pre-exercise and at the end of each minute of the test. A mean skin temperature was calculated from these measurements (Dawson, 1994). Tympanic temperature was measured pre-exercise and immediately post-exercise using a tympanic thermometer (Braun Pro 3000 ThermoScan).

Subjective ratings of the cold were taken pre-exercise, and during the final minute of the test. For this the players were required to state how they felt at the time, whether they were not cold at all, slightly cold, moderately cold, very cold or extremely cold (see more). Rating of Perceived Exertion (RPE) using a 10 point scale (Borg, 1982) was also recorded during the final minute of the test. This required them to state how difficult the exercise felt at the time, ranging from nothing at all (0) and very very light (0.5) to maximal (10).

Hockey Game

The following parameters were measured on nine of the players from the Northern region of Australia during four hockey games (one practice game and three tournament games).

Heart rate was recorded using a heart rate monitor set to record the average of every five second period. The monitor was worn around the chest, with the recorder watch strapped to the back of the players. The heart rates were later downloaded from the watch onto a computer and analyzed. Core body temperature was estimated by the measurement of tympanic temperature using a tympanic thermometer. Temperatures were recorded pre-game, at half time, whenever a player was substituted off the playing field, and post-game. Body mass was measured in minimal clothing before and after the game, and fluid consumption by weighing of individual drink bottles was measured during the same time period, for determination of fluid intake, sweat losses and fluid balance. Playing position and time on field was recorded. Immediately after the game the players were also asked to rate subjectively the cold and RPE during the game.

Perceptions of the environmental conditions and game performance were obtained from a post-game questionnaire, from all players following several games (Appendix 4). Also after several games a modified short form Profile of Mood States (POMS) questionnaire was administered.

Fitness Tests

The multistage fitness test (Australian Sports Commission, 1998) (also known as the shuttle run test or beep test) was performed on all northern region players. Body fat measures (sum of seven skinfolds) were also recorded on all players from the NT team.

Daily Measures

The POMS questionnaire was also administered approximately every third day early morning. While in Hobart, this was completed during breakfast, when all players were present. All players completed a daily questionnaire (Appendix 6) early every morning, in which they had to record their morning heart rate, sleep patterns and rank physical as well as psychological states.

Environmental conditions

The environmental conditions were recorded for each game, immediately prior to the game, and half time, and at the end of the game, using a portable weather instrument (Kestral 3000 Pocket Weather Meter, Nielsen-Kellerman). The measurements included air temperature, relative humidity, average wind speed, and rain conditions were also recorded. The weather conditions for all days from two weeks prior to the tournament until two weeks after the tournament were also gained from the weather bureau.

Data Analysis

Correlations of multistage fitness test scores as a measure of aerobic fitness and the physiological and psychological responses to exercise in the cold will be determined.

RESULTS

Player Data

Average body mass was 63.9 ± 9.5 kg (range 49.8 to 83.7 kg). The sum of seven skinfold sites was 101.6 ± 36.9 mm (range 72.7 to 189.1 mm). The average multistage fitness test result was level 9/4. The range of scores were 5/9 to 11/4. This equates to a predicted VO2max of 44.4 ± 5.5 ml.kg.min-1.

The Northern Region players had lived at their current location for on average 16 years, and had played hockey for an average of 11 years.

GAME RESULTS

The NT U/21 female team played several practice games in Darwin prior to departure, and one practice game against the local team in Tasmania the day after arriving. The tournament consisted of 7 regular games and two final matches. Measurements were taken on nine players, during four games each (one practice and three tournament games). The NT team finished in seventh position. The game results and environmental conditions where known are presented in Table 1.

TABLE 1: Game results and environmental conditions.

date game opposition result temperature humidity wind




(degrees) (%) (m.sec-1)

June 21

Practice

NT mens vets

?

25.6

74

?

June 28

Practice

Banks

?

24.5

76

?

July 5

Practice

Warratahs

?

27.2

61

0.3

July 9

Practice

TAS local

Won

13.3

71

0.3

July 11

Tournament

TAS U21

Drew 1-1

12.5

58

0.6

July 12

Tournament

WA

Lost 6-1

10.5

71

0.5

July 13

Tournament

ACT

Lost 6-1

?

?

?

July 15

Tournament

QLD

Lost 2-0

13.2

72

0.3

July 16

Tournament

NSW

Lost 2-1

13.7

63

0.7

July 18

Tournament

SA

Lost 3-0

?

?

?

July 19

Tournament

VIC

Lost 6-0

9.8

79

0.5

July 21

Semi-final

VIC

Lost 5-2

7.1

89

2.0

July 22

classification

TAS

Drew 1-1

14.2

63

0.2

The Practice games in Darwin prior to the tournament were played in the evenings when the environmental conditions were not as severe. Though compared to the conditions encountered in Hobart, there was a very big difference. The game conditions in Hobart averaged 11.8 oC and 70.8 % humidity compared to 25.7 oC and 70.3 % humidity in Darwin.

Heart Rates

Only complete data is available for seven of the nine players, due to missing data and for some data being rejected due to less than half a game completed. The data is presented for each group of players analyzed.

Figures 1-3 shows the percentage of time spent in each heart rate range for the practice and tournament games, for groups 1 (Figure 1) and 2 (Figure 2) and for all seven players combined (Figure 3).

All graphs show the practice game in Darwin was of a lower intensity, with 60-75% of the time with heart rates below 90% of maximum, compared to generally less than 40% for the tournament games.

The graph of the average heart rates for all subjects (Figure 3) indicates a trend for lower heart rates during the last games of the tournament. However, looking at each group shows that this is a result of differences for only group 1. For group 2 (Figure 2), the results for the three games in Tasmania were similar. For group 1 (Figure 1), the heart rates during the final game were much lower, similar to the Darwin game

Figure 1: Percentage of time in each heart rate range (as a percentage of maximum heart rate) for the practice and tournament games, for group 1 (n=3).

table

Figure 2: Percentage of time in each heart rate range (as a percentage of maximum heart rate) for the practice and tournament games, for group 2 (n=4).

table

Figure 3: Percentage of time in each heart rate range (as a percentage of maximum heart rate) for the practice and tournament games, for all subjects (n=7).

table

Sweat rate and fluid intake

Though sweat loss tended to be lower as the tournament progressed, there were differences in fluid intake which compensated for this. Therefore, the net changes in body mass were similar for all games (Table 2).

The change in body mass as a percentage of initial body mass was only small (average range (-0.1 to -0.4%). If there was no fluid intake, the average body mass loss would have been 2.0% in Darwin down to 1.3% for the last game in Tasmania.

TABLE 2: Average body mass changes, fluid intake and sweat loss during hockey games.

Game Body mass decrease Fluid intake Calculated sweat loss

(kg)

(l)

(l)

Darwin

0.23 ± 0.49

0.97 ± 0.29

1.19 ± 0.25

TAS 1

0.27 ± 0.53

0.70 ± 0.28

0.97 ± 0.45 *

TAS 2

0.07 ± 0.44

0.71 ± 0.26

0.84 ± 0.43 *

TAS 3

0.19 ± 0.43

0.57 ± 0.26 *

0.77 ± 0.32 *

* significantly different from Darwin value.

Tympanic temperature

The core body temperature as estimated by the measure of tympanic temperature was higher in Darwin as expected. There was a general trend of decreasing values from the before warm-up to post-game for all games. The lowest values were from the final games of the tournament which also corresponded to the coldest games.

TABLE 3: Average tympanic temperature (degrees Celsius) before, during and after hockey games in Darwin and Tasmania.

Game initial Post-warm-up Half-time Full-time

Darwin

37.2 ± 0.3

36.7 ± 0.7

37.1 ± 0.6

36.5 ± 0.5

TAS 1

36.5 ± 0.5

36.0 ± 0.5

36.1 ± 0.7

35.8 ± 0.6

TAS 2

36.7 ± 0.7

36.2 ± 0.8

35.8 ± 0.8

35.6 ± 0.8

TAS 3

36.0 ± 0.7

35.3 ± 0.9

35.0 ± 1.2

34.6 ± 1.1

Figure 4: Average tympanic temperature (degrees Celsius) before, during and after hockey games in Darwin and Tasmania.

ear temp chart

Post-game comments

In response to the post-game questionnaire question asking in what way did the cold affect their performance, the answers were categorised into several general responses (Table 4).

TABLE 4: Post-game comments, summarised into generalised comments.

Response Number
difficulty getting and staying warm 13
ventilatory problems 12
cold body parts 10
felt fitter, could run more 7
hard to hit / control ball 6
difficulty concentrating 5
other 9

STEP TEST RESULTS

The NT squad performed five step tests (pre and post the tournament, and three in Tasmania). The ACT squad performed four test, missing the third test in Tasmania.

Table 5: Average results for the ACT and NT squads step tests. Statistics were performed separately on the pre-post data, and the Hobart data.

Pre Tas 1 Tas 2 Tas 3 Post
Number of subjects NT 7 8 8

8

7

ACT 5 3 3

3

5

Temperature

oC

NT 23.0 14.3 10.3

10.3

22.5

ACT 17.1 13.6 8.2

17.6

Humidity

%

NT 60 63 67

62

50

ACT 61 61 66

69




Coldness Rating NT 1.4 2.6 2.4

2.5

1.0

Pre test

ACT 1.6 2.2 3.3

1.6

Coldness rating NT 1.4 2.0 2.0

1.8

1.0

Post test

ACT 1.0 1.2 1.8

1.0




Blood lactate

mmol.l-1

NT 4.7 4.1 4.0

3.4

3.9

Post test

ACT 3.2 2.6 2.2

3.5

Tympanic temp

oC

NT 36.6 36.7 36.6

36.6

36.2

Post test

ACT 36.8 36.7 35.8

36.4

Mean skin temp.

oC

NT 29.9 27.6 27.6

27.8

30.7

ACT 28.6 26.9 25.6

27.8

Max. heart rate

B.min-1

NT 171 172 170

167

165*

ACT 165 168 169

-

170

* significantly different from pre

DISCUSSION

As the amount of adipose tissue can affect temperature regulation, it would be interesting to look at the correlation of skinfold measures and body surface area to the physiological and psychological responses (e.g. cold ratings) to exercise in the cold.

As fitness level can also affect responses to the cold (as fitter players have a better vasoconstriction mechanisms, greater muscle mass for heat productions, and can maintain higher intensity exercise for longer periods and therefore maintain high levels of heat production), does this affect responses?

Game heart rates

The lower game intensity in Darwin, as indicated by the heart rate measures, was as expected due to the decreased importance of the results, and the lower standard of competition. The higher temperature in Darwin, making prolonged high intensity exercise difficult, may also have added to the lower game heart rates.

The lower heart rates for group 1 during the final game may be a result of the lower temperature. These measures were recorded during the semi-final, which was the coldest game they played during the tournament (Table 1). It was an important game in terms of the results, so the motivation to try hard should have been high.

Sweat rate and fluid intake

Sweat loss tended to be lower as the tournament progressed. This may have been an adaptation to the cold conditions, though it may also have been a reflection of the differences in conditions, as the last games were also the coldest games.

The percentage loss in body mass was only small, even in Darwin, and would not be expected to affect performance. This was a consequence of good fluid replacement strategies by all the players.

Tympanic temperature

The body temperature measurements were estimated using a tympanic thermometer. While these results showed differences which seemed to reflect the changes in external temperature, some of the values recorded were outside the possible range for normal core temperature (<34 oC). This places some doubt on the accuracy of these measures to reflect core temperature. The temperature measure appears to be affected by the air temperature around the ear, and the ear skin temperature.

Post-game comments

Of the post-game comments, the difficulty warming up or staying warm was of greatest concern. Although the warm-up procedures were attempted to be more extensive than usually performed in Darwin, due to the tournament conditions, they were only allowed onto the playing surface for the half hour prior to the game. Consequently, the warm up was sometimes rushed. Also, at half time the preferred option was to go into the change room to keep warm. However, due to limited time and availability of the change rooms this was not possible.

Comments such as ventilatory problems, cold body parts, difficulty concentrating represent external distractions which may affect the game performance. The cold hand, making hitting and controlling the ball difficult, affect the player's skill directly. The only positive comments were that some players felt they could run for longer or harder in the cold conditions.

CONCLUSIONS

It is always difficult to analyze game data as there are many variables to consider, making the interpretation of results difficult. Although there were differences as the tournament progressed, it is hard to know whether this was due to adaptation to the cold, or because the last games of the tournament included to coldest games.

RECOMMENDATIONS

REFERENCES

APPENDIX 1: Step test proforma

STEP TEST PROFORMA

Name: ______________________ Date: ______________ time: ___________ Body weight: _________________ Age: _________ 90% predicted max HR (0.9 x 220-age): _____________

Clothing: ___________________________________________________________ Step height ___________ Stepping rate ___________ test time: ___________ ENVIRONMENTAL CONDITIONS: Location: ________________________________________________ Temperature __________________ Humidity __________________ Wind __________________ Heart rate monitor number: ___________

RPE Coldness rating* Blood La- Auditory temp chest temp forearm temp calf temp
Pre-exercise
minute 1
minute 2
minute 3
minute 4
End/post-ex

APPENDIX 4: post game questionniare

POST-GAME QUESTIONNAIRE

Name: ________________________ date: _________ time: ________

Please complete all of these questions below

How would you rate your physical effort (not skill performance)?

  • Poor
  • Below average
  • Average
  • Good
  • Very good

How would you rate your skill performance ?

  • Poor
  • Below average
  • Average
  • Good
  • Very good

Which of the following best describe how you felt during the game?

  • Not cold at all
  • Slightly cold
  • Moderately cold
  • Very cold
  • Extremely cold

How much do you think the environmental conditions affected your game?

  • Not at all
  • Slightly affected
  • Moderately affected
  • Greatly affected
  • Extremely affected

Describe the way in which the cold affected your performance today, if you feel it did so.

__________________________________________________________

__________________________________________________________

__________________________________________________________

 

APPENDIX 6: Daily Questionnaire

DAILY DIARY name: _________________________

Please fill in the appropriate number, or circle your results on how you feel about each of the areas below. Do this first thing every morning. Circle your results from 1 to 5 (1=very good, 2=good, 3=OK or average, 4=below average, 5=poor)
day date Body weight Resting heart rate No. of hours sleep Quality of sleep Muscle soreness General health comments
Sunday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Monday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Tuesday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Wednesday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Thursday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Friday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Saturday

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

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