Hematological and biochemical changes during a short triathlon competition in novice triathletes

Eur J Appl Physiol (1990) 61:93-99 European Journal of Applied Physiology

and Occupational Physiology © Springer-Verlag 1990

Hematological and biochemical changes during a short triathlon competition in novice triathletes

Dale Long, Mark Blake, Lars Mc Naughton, and Brian Angle

Tasmanian State Institute of Technology, Centre for Physical Education, P. O. Box 1214, Launceston, Tasmania 7250, Australia

Accepted January 16, 1990

Summary. Short-course 'sprint' triathlons have become popular in recent years, often as a precursor to the longer full-course triathlons. We undertook a study investigating the haematological and biochemical changes that occur in novice triathletes between the start and finish and after each of the three legs of a short sprint triathlon involving swimming, cycling and running. The changes that occurred in the triathlon in- cluded a significant ( P < 0.003) decrease in weight from 71.7 kg, SD 7.9 to 70.3 kg, SD 7.6. Throughout the time span of the triathlon, the white blood cell count increased significantly (P<0.001), as did the platelet count (P<0.005) and plateletcrit (P<0.001). There were no significant changes during the period of the race in any of the other haematological variables measured. The biochemical variables measured were glucose, triglycerides, sodium, potassium, calcium, lactate dehydrogenase, creatinine and aspartate aminotransferase. Triglyceride, calcium and potassium values did not change between the pre- and post-race samplings. All other biochemical parameters showed a significant change (P<0.05 or better). Changes that occurred in the haematological and biochemical parameters between stages were many and varied. There was also a significant change in plasma volume during the swimming event ( P < 0.001), but this returned to normal during the later stages of the triathlon. In conclusion the changes that occurred during the triathlon were many and were similar to those reported elsewhere in the literature for longer events. The novice triathletes who participated, found this short triathlon to be as stressful as the full-course triathlon is for the more experienced athlete. We feel, however, that this type of event is use- ful as a precursor to the longer type of events.

Key words: Novice - Short triathlon - Blood profile - Biochemical variables - Plasma volume

Introduction

Triathlon competitions have become very popular in the last 10 years. The original triathlon was the Hawaii

Offprint requests to: L. R. Mc Naughton

Iron Man Competi t ion held in 1978, which started with 14 competitors and now boasts more than 1200 participants. In most cases these endurance athletes must par- ticipate in swimming, cycling and running but on some occasions other activities have been used such as ca- noeing, skiing and running or cycling, running and skiing (van Rensburg et al. 1986). The popularity of the sport can be gauged by the number of participants in the United States alone, an estimated 800000 in 1984 (O'Toole et al. 1987).

'Sprint' triathlons, which are shortened versions of the longer triathlons, usually involve swimming dis- tances of 1-1.5 km, cycling 30-40km and running 10 km. These events have become popular as they are a 'half-way' stage for the less well trained and the highly trained triathlete and allow the less well trained athlete to become accustomed to the rigors of competition. Some work has been undertaken to investigate the physiological responses of triathletes (Kohrt et al. 1987) to exercise of various types and profiles of typical triathlons (Holly et al. 1986) and ultraendurance triath- Ions (O'Toole et al. 1987). Much has been written re- cently of the physiological and biochemical changes that occur in triathlons (O'Toole et al. 1987; van Rens- burg et al. 1984, 1986), as well as the haematological changes that take place during triathlons (Davidson et al. 1987). The aim of this study was to determine the physiological and haematological changes that occurred in novice triathletes during a short sprint triath- Ion.

Methods

Subjects. Ten men participated in this study and gave written informed consent after being informed of the risks involved. These athletes had never performed a triathlon prior to this date and had never taken part in any competitive running, cycling or swimming event. However, they had trained specifically, for at least 3 months prior to the event taking place. The sprint triathlon took place within the city of Launceston, Tasmania, Australia. The first leg consisted of a 1.0-km swim, the second being a 30.0-km cycle ride, and finally there was a 10.0-km run. The physical character- istics of the subjects are described thus (mean and SD), age 26.2

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years, SD 4.3, height 179.3 cm, SD 6.4, weight 71.7 kg, SD 7.9 kg. The weather on the day of competition was overcast with periods of showers. There was little wind and the temperature was 19 ° C.

Protocol. Prior to the start of the triathlon 10 ml blood was taken from the antecubital vein and the subjects were weighed. Blood was again taken after the swim stage, the bicycle stage and at the end of the running stage. The subjects were again weighed at the end of the triathlon. Blood samples during the course of the triathlon were taken in the following positions: pre-race, standing; post-swim, lying; post-cycle, sitting; post-run, standing.

Analysis. Haematological analysis, consisting of a 12-parameter profile, was performed using a Coulter counter (model S Plus II). This was performed immediately after blood collection.

Biochemical analysis of the following parameters was carried out calcium, glucose, sodium, potassium, creatinine, triglycerides, lactate dehydrogenase and aspartate aminotransferase. The sodium, potassium and creatinine analysis was performed using a Beckman Astra 4. This has electrodes selective for sodium and potassium ions and measures creatinine using the alkaline picrate method. All other blood chemistries were performed on a Roche Cobas Mira.

Statistical analysis was performed on all of the collected data. Comparisons between means were undertaken with Student's t- test and, where multiple comparisons were carried out, an analysis of variance (ANOVA) with repeated measures was used. The Scheff6 test was used as a correction for multiple comparisons (Keppel 1982).

Results

The complet ion time for the short-course sprint triath- Ion was 130.8 min, SD 8.9 min, the swim stage taking 23.4, SD 7.7 min, the cycle stage 61.4 km, SD 5.6 and the running stage 49.5 min, SD 3.6. There was a significant ( P < 0.003) decrease in weight during the course of the event with weight decreasing f rom 71.7 kg, SD 7.9 to 70.3 kg, SD 7.6

Haematological variables

All of the ten subjects showed a normal b lood profile prior to the start of the triathlon.

The b lood indices (mean and SEM) of the ten subjects before the short-course triathlon and after each leg are shown in Table 1. There was a highly significant change in while blood cell (WBC) count across the total triathlon, all stages being significantly different f rom each other ( P < 0.001). There was a significant change in platelet count f rom the start to the finish of the tr iathlon ( P < 0.005) and this was also the case for plateletcrit ( P < 0.001). There were no changes in mean cell haemoglobin (Hb) or mean cell Hb concentration. All other measures had highly significant (P<0.01 or greater) differences between subjects indicating that subjects behaved differently during the triathlon to such an extent that the results varied greatly. The following breakdown analyses the results between each stage of the triathlon.

Pre-race post-swim. WBC increased significantly (P<0.05), as did red blood cells (P<0.05). Hb levels increased by 2.4%, which was a significant increase (P<0.05) and there was a 4.2% and 6.5% increase in haematocr i t (haematocr i t /packed cell volume, P < 0.05) and mean cell volume respectively (P<0.01). All subjects showed a small increase in platelet count and also in plateletcrit with a mean increase attaining statistical significance (P<0.05). Values for the red cell distribution w id th decreased significantly during this t ime (e<0.05).

Post-swim post-cycle. The increase in WBC between the post-swim and post-cycle b lood collection stages was significant ( P < 0.05). The red b lood cell count, however, decreased significantly (P<0.05) during the same period of t ime and attained its pre-race level. There was a similar occurrence for Hb, which decreased significantly ( P < 0.05), but this value was still higher than the initial pre-race level ( P < 0.05). Mean cell Hb and mean cell Hb concentration values did not change during this t ime but red cell distribution width increased significantly (P<0.05) after an initial decrease, and at this point was similar to initial pre-race values. Haematocr i t or the packed cell volume decreased by 8.2% f rom the

Table 1. Blood indices [mean (SEM)] before the triathlon and after each of the three stages

Blood indices a Pre-race Post-swim Post-cycle Post-run

10-9×WBC (1-') 6.01 (0.7) 9.86 (1.4) 10-~2× RBC (1-1) 5.03 (0.3) 5.23 (0.3) Hb (g dl) 14.84 (0.8) 15.79 (0.8) Hct (1/1) 0.47 (0.03) 0.49 (0.02) MCV (fl) 93.0 (3.6) 93.96 (3.8) MCH (pg) 30.5 (2.6) 30.30 (1.1) MCHC (g dl) 31.8 (1.7) 32.34 (0.4) RWD 10.24 (0.8) 9.67 (0.5) 10-9 x PLT (l -1) 240 (39.5) 309 (49.0) Pct (%) 0.29 (0.02) 0.33 (0.03) MPV (fl) 9.86 (1.3) 10.54 (1.1) PDW 7.01 (0.2) 7.02 (0.4)

10.36 (3.1) 15.08 (4.1) 5.02 (0.3) 5.03 (0.3)

15.30 (0.7) 15.36 (0.6) 0.45 (0.01) 0.47 (0.02)

93.0 (3.6) 93.4 (3.6) 31.3 (2.1) 30.5 (1.2) 32.9 (1.2) 32.63 (0.3) 10.29 (0.7) 10.6 (0.8)

303 (47.6) 312 (36.7) 0.33 (0.05) 0.33 (0.02)

10.56 (1.2) 10.58 (1.3) 7.1 (0.3) 7.1 (0.3)

a WBC, White blood cells; RBC, red blood cells; Hb, haemoglobin; Hct, haematocrit; MVC, mean cell volume; MCH, mean cell Hb; MCHC, mean cell Hb concentration; RDW, red cell distribution width; PLT, platelets; PCT, plateletcrit; MPV, mean platelet volume; PDW, platelet distribution width

Table 2. Changes in plasma and red cell total blood volume after each stage of the sprint triathlon [mean (SEM)]

Blood Volume (%) constituent

Pre-race P o s t - s w i m Post-cycle Post-run

Plasma 53.0 (3.1) 50.2 (3.1)* 47.93 (2.1)* 53.34 (4.4) Red cell 47.0 (3.1) 46.05 (2.9) 43.65 (1.9)** 45.41 (2.9) Total blood 100 93.98 (1.9)* 96.99 (2.2)** 96.61 (3.8)

* P<O.O01 ** P<O.Ol

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post-swim stage and this was significantly lower (P<0.05). There were no significant changes in either platelet count, plateletcrit or platelet distribution width. There was a small but non-significant increase in mean platelet volume during this time. The mean cell volume remained constant throughout this period also.

Post-cycle post-run. The WBC count once again increased above the value measured at the post-cycle stage. Haematocrit levels rose during this period to the same level as prior to the start of the triathlon. This increase was significant (P< 0.05). All other blood indices remained constant for this particular comparison.

Plasma volume changes. The Hb concentration and haematocrit were used te calculate plasma volume changes according to the formula of Dill and Costill (1974). These changes can be seen in Table 2. The largest decrease in plasma volume occurred after the first stage of the event (swimming). During this time the plasma volume decreased by 9.57 _+ 2.8% (P< 0.001). This was then followed by an increase back to pre-race levels (P<0.001) after the cycling stage.

Biochemical parameters

The values for all of the biochemical parameters measured can be seen in Table 3 and are given a mean (SEM). Sodium levels increased when the pre- and post-race samples were compared. In the first instance

the level was 141.9 (2.9) mmol 1-1, whereas the post- race sample measured 147.4 (2.5) mmol 1-1. This was not true, however, for calcium levels, which remained unchanged. In this case the pre-race measurement was 2.46 (0.08) mmol 1-1 while the post-race sample was 2.49 (0.09) mmol 1-1. There were no significant changes in blood triglyceride levels between the pre- and post- race samples. The pre-race value was 1.4 (0.68) mmol1-1 while the post-race value was 1.5 (0.29) mmol 1-1. Blood glucose levels, however, were significantly elevated after the race when compared with the pre-race values ( P < 0.05). The mean pre-race value was 5.1 (0.83) mmol 1-1, while in the post-race condition the mean value was 6.2 (0.64) mmol 1-1.

Lactate dehydrogenase values rose between the be- ginning of the race and the end of the triathlon (P<0.05). The pre-race value was 260.2 (83.9) IU 1-1 and this increased to 400 (91.6) IU 1-1 by the end of the running stage. Creatinine levels also increased throughout the race. When the pre-race values were compared with the post-run values there was a significant increase (P<0.05). The pre-race value was 75.4 (9.8) mmol 1-1 while the post-race value was 102.0 (14.1) mmol 1-1

Aspartate aminotransferase also rose significantly throughout the three stages of the race. The pre-race level was 26.4 (3.9) IU 1-1 while the post-race value was 34.3 (5.2) IU 1-1 (P<0.05). Potassium levels remained unchanged between pre- and post-race sampling. The pre-race sample was measured at 4.4 (0.3) mmol 1-1 while the post-race sample was measured at 4.4 (0.2) mmol 1-1.

Table 3. Biochemical parameters throughout the course of the triathlon [mean (SEM)]

Parameter" Pre-race Post-swim Post-ride Post-run

Na + (mmol 1-1) 141.9 + 2.9 143.7 + 3.0* 147.4 + 2.7*** 147.4 + 2.5** Ca 2+ (mmol 1 -~) 2.46+ 0.08 2.56+ 0.03* 2.52+ 0.08 2.49+_ 0.09** Glu (mmol 1-1 ) 5.1 _+ 0.83 5.1 + 0.80 5.4 + 0.79 6.2 + 0.64*** Trig (retool 1 -~) 1.4 + 0.68 1.5 + 0.62 1.4 + 0.35 1.5 + 0.29 LDH(IU1-1) 260.2 +83.9 315.3 +81.6" 347.6 +-50.0*** 400.0 ___91.6 a'*** ASP(IU1-1) 26.4 + 3.9 29.6 + 5.3* 28.6 + 5.6 34.3 +- 5.2*'*** K + (mmoll -~) 4.4 + 0.3 4.4 + 0.4 4.6 + 0.4 4.4 + 0.2 CRT(mmol1-1) 75.4 + 9.8 94.2 +-11.2" 96.9 +12.7"** 102.0 +14.1"**

a Trig, triglycerides; LDH, lactate dehydrogenase; ASP, aspartate aminotransferase; CRT, creatinine * Significantly different from preceding measure (P< 0.05) ** Significantly different from post-swim stage (P< 0.05) *** Significantly different from pre-race values (P<0.05)

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Pre-race post-swim. Sodium levels increased significantly during this stage (P< 0.05) as can be seen in Ta- ble 2. Values shown are mean (SEM) calcium levels also rose to be significantly higher than pre-race values (P< 0.05). There were no changes in blood glucose, triglyceride or potassium levels during this phase of the competition.

LDH values rose between the pre-race and post- swim samples. The pre-race value was 260.2 (83.9) IU1 -~ while the post-swim value was 315.3 (18.6) IU 1 -~ (P< 0.05). Aspartate aminotransferase rose during this stage also to be at 29.6 (5.3) IU 1 -~ (P<0.05). Finally creatinine also increased during this stage to a value of 94.2 (11.2) mmol 1 -a (P<0.05).

Post-swim post-cycle. Sodium levels increased slightly during this stage of the race to 147.4 (2.7) mmol 1-1 (P< 0.05). Calcium levels dropped slightly to 2.52 (0.08) mmol 1 -~, but this was not significant. However, the value was still significantly higher than the pre-race value (P< 0.05). Blood glucose, triglycerides, potassium and creatinine levels remained unchanged from their post-swim values.

Lactate dehydr0genase levels again rose significantly (P< 0.05) at the end of this stage and were 347.6 (50.0) IU 1-1. Aspartate aminotransferase rose again to a value of 31.9 (5.1) IU 1 -a (P<0.05).

Post-cycle post-run. There were no changes in the values of blood sodium, calcium, glucose, triglycerides, potassium or creatinine during this stage of the race. Lactate dehydrogenase values again rose to a high of 400.0 (91.6) IUI -~ (P<0.05). The same is true of aspartate aminotransferase, which rose significantly (P< 0.05) to 34.3 (4.2) IU 1-1.

Discussion

This study has reported the many changes in the haematological and biochemical responses of novice triathletes to a short-term sprint triathlon.

Haematological data

Of initial interest is the elevation in the WBC count during almost 2 exercise. This is in agreement with a recent study by Galun et al. (1987), who found in- creases in while blood cells after both short-term and long-term marching. They, as others have done (Finch 1977), would suggest that the elevated WBC count is pseudo-leucocytosis, which has been shown to occur with elevated levels of physical stress, probably because of to increased levels of plasma adrenaline, thus mobil- izing WBC from the marginal pool to join the circulat- ing pool (Jedrzejezak 1979). Other studies have found similar results when investigating other endurance-type events suchas the marathon (Davidson et al. 1987) and full-course triathlons (Davidson et al. 1986).

The largest change in WBC count occurred during

the run stage. This would be appropriate given the work of Finch (1977) and Jedrzejezak (1979). This period of work involves the greatest amount of muscle mass and, with the constant repetitive force being placed upon the hard road surface, it has in our opin- ion, the largest amount of physical stress. Furthermore, it also involves the greatest energy involvement, approximately 3.1 MJ in comparison with approximately 1 MJ for swimming, and 2 MJ for cycling (Williams 1983).

The lack of any significant change in the red blood cell count is likely, owing to the relatively small num- bers, to have been masked by the variability between subjectsl Although no major changes occurred, over the full period of the triathlon there were, at varying times both statistical and non-statistical changes in mean values for cell Hb, Hb concentration, volume and red cell distribution width, which when taken together might in- dicate an increased mobilization and release of larger and younger red cells over the course of the triathlon (Davidson et al. 1986). If this was not the case, then it could be due to small changes involving red cell defor- mability, and/or changes in water content and mem- brane permeability (Galea and Davidson 1985).

The increase in platelet count during the initial phases of the triathlon are in agreement with those of Davidson et al. (1986, 1987) but are smaller than those reported in either the marathon or full-course triath- Ions. The changes in platelet count mimic closely, as would be expected, the WBC count. Again platelets are expected to increase in relation to stress, and major changes occurred during the most stressful periods of the triathlon. This increase in platelets probably comes from the spleen, as the major platelet-releasing organ, but there is also the possibility of a co-existing intravas- cular marginal pool within the pulmonary circulation (Schmidt and Rasmusson 1984).

The changes in Hb and haematocrit are very similar to those reported by Davidson et al. (1986). In the first case there was an initial increase, which was then followed by a decrease buth not back to pre-exercise levels, and this in turn was followed by another light increase; however, this was not to the level of the first increase. In terms of haematocrit the picture was similar to that of Hb, an initial increase at the end of the first exercise period followed by a slight decrease, followed in turn by another slight, insignificant increase. In general our values for haematocrit levels were slightly higher than those of Davidson et al. (1986) and were at normal reference levels (Davidson et al. 1987).

There is a wealth of conflicting information con- cerning the lower Hb and haematocrit values often seen in well-trained endurance athletes. Two recent edito- rials have provided an up-to-date critique of the area (Hallberg and Magnusson 1984; Lancet 1985) but the principal finding is that the so-called sports anaemia is caused by the dilution effect of increased plasma volume exceeding the increase of the red cell mass, analo- gous to the situation found during pregnancy (Hytten and Paintin 1963).

The changes in plasma volume calculated in this

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study are similar to those shown by Davidson et al. (1986, 1987). The shift in plasma volume appeared to be maximal after the end of the first stage of exercise (swimming), which is surprising in light of the similar finding by Davidson et al. (1986) where the first stage was cycling. They suggested that maintenance of plasma volume after this initial stage was due to the availability of fluid to the athletes, but during swimming, fluid is readily available; hence one would not expect such a drop in plasma volume. Hagan et al. (1978) have indicated that rapid plasma volume changes found during exercise are more likely to be due to postural factors than to the intensity or type of exercise being undertaken. We feel this could well explain the changes seen during this study in the swimming stage where postural changes are greatest from rest. Ha- gan et al. (1978) have attributed as little as 1% of plasma volume changes to exercise.

We are at a loss to explain the difference between the results of this study and the results of another similar study from our laboratory (Mc Naughton 1989). During a sprint triathlon of similar duration, plasma volume decreased by 14.3% compared with a resting control change of 6.2%. In this instance the difference of 8.1% was attributed to exercise. In the present study, however, the largest change noted was a decrease of 6.1% during the cycling stage. The Mc Naughton study (1989) found a 2% change during control sitting so it may well be, in this case, that the exercise played a larger part than in previous work, at least during the cycling stage. The changes in plasma volume seen after exercise may be determined not ony by the type of exercise but also by other factors, such as the hydration of the subject, posture and intensity. It has been suggested that the mechanisms of fluid shifts that occur in such events as cycling and running might be quite different (Senay et al. 1980).

Biochemical data

The lack of change for serum triglyceride values is in agreement with several other marathon and triathlon studies (Maron et al. 1975; McKechnie et al. 1982; van Rensburg et al. 1986). There have been reports of both decreased and unchanged levels of serum triglycerides in long-distance cross-country skiers (Carlson and Mossfeldt 1964) but, unlike intramuscular stores of triglycerides, which have been shown to contribute significantly to energy metabolism (Essen 1977; Essen et al. 1977), the importance of blood-borne triglycerides has not been established (van Rensburg et al. 1986). We believe that triglycerides probably play only a small part during endurance activity of this length, especially with athletes not at the elite level. Free fatty acids are more likely to play a substantial role in longer exercise and also with the more highly trained aerobic athlete.

During this short triathlon no competitor developed hypoglycaemia, the lowest blood glucose value being 3.8 mmol 1-1. This is in agreement with the findings of van Rensburg et al. (1986) during full-distance triath-

Ions. The results of this study, with regards to elevation of glucose levels throughout the race, are generally in agreement with other studies employing endurance- type activities (Jooste et al. 1981; Maron and Horvath 1978; Maron et al. 1975; Noakes and Carter 1976; Scheele et al. 1979; van Rensburg et al. 1986). This increase in glucose is probably due to a three- to fivefold increase in glucose output from the liver (Costill 1984; Ahlborg and Felig 1982). The increase in glucose cannot be attributed to the ingestion of food or sweetened liquids as only water was available to the athletes throughout the course of the experiment (though few athletes availed themselves of this). It should be noted, however, that cases of hypoglycaemia have been reported in highly competitive runners (Kelly and God- lonton 1980), since liver glcuose output cannot con- tinue to keep pace with glucose uptake by the muscle (Felig and Wahren 1975).

The elevations in lactate dehydrogenase that occurred in this study are in agreement with those reported elsewhere in the literature (Kielblock et al. 1979; van Rensburg et al. 1986). The changes here are smaller than those reported, and this is probably due to the duration rather than the intensity of the exercise for these particular athletes. The increase in lactate dehydrogenase could have been produced through the increased need to convert lactic acid back to pyruvic acid, or it may have been produced in response to the need to convert pyruvic acid to lactic acid at the end of each of the stages where the athletes would have been working at higher levels (McArdle et al. 1986). In the study by van Rensburg (1986) the distance, and therefore the time taken for the event, was substantially longer than this short triathlon.

The changes that occur to aspartate aminotransferase are generally regarded as contradictory. There have been reports of no effect of moderate exercise in subjects accustomed to exercise: an increase above normal that returns to normal while exercise is continued (Henry et al. 1974) or just after exercise (Tietz 1987). In real terms, the changes that occurred during the course of the triathlon are small, albeit significant, and are probably caused by leakage from the muscle cells. It is generally considered that aspartate aminotransferase is not a significant indicator of muscle damage however, it is used as a liver function test in conjunction with other enzyme tests. Many factors have been described as influencing the degree of rise in enzyme activity, in- cluding type of activity and intensity and duration of activity, as well as the climatic conditions under which the activity was carried out (Critz and Cunningham 1972; Fowler et al. 1968; Magazanik et al. 1974; Wynd- ham et al. 1974).

In this study we noticed a significant increase in serum calcium and serum sodium after the start of the triathlon. This is in general agreement with other reports on endurance-type activities of this duration (Cohen and Zimmerman 1978; Dancaster and Whereat 1971). Interestingly, Imelik (1981) reported a similar increase in Ca 2+ following only the swimming exercise and not running or cycling, as was seen in this experi-

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ment. Whe the r it can be related only to this type o f exercise is unc lear at this time. Krebs et al. (1983) ex- p la ined the rise in serum N a + by the vo lume contrac- t ion occurr ing, as shown by an increase in serum pro- tein. With regards to po tass ium concent ra t ion fo l lowing the tr iathlon, we saw no significant changes. There have been reports bo th o f decreased levels o f po tass ium following endurance activities (Cohen and Z i m m e r m a n 1978; Dancas te r and Wherea t 1971; M a r o n et al. 1975; and Olivier et al. 1978) and o f increased levels o f potas- s ium fol lowing m a r a t h o n events (Rose et al. 1970). Sev- eral invest igators have shown decreases in muscle K + and an increase in venous K + levels dur ing exercise but at present it is no t clear whether certain types o f exercise m a y inf luence a specific ionic gradient (Korge and Viru 1971; Sreter and F r i edman 1963). Rises in serum K + have been expla ined by bo th vo lume contrac- t ion and an efflux o f K + f rom intracel lular stores, which in effect reflects a loss o f muscu la r g lycogen (Taun ton et al. 1986). One wou ld expect a loss o f gly- cogen f rom muscle tissue dur ing the course o f the t r ia thlon bu t possibly the losses were not s ignif icant enough dur ing this activity to effect undu ly the eff lux o f K + f rom intracel lular stores.

The increase in creat inine concen t ra t ion due to endurance exercise is similar to that repor ted elsewhere (van Rensburg et al. 1986; Whit ing et al. 1984). The decreased renal b lood f low and hence g lomeru la r filtra- t ion rate, dehydra t i on and hence hypovo l a e m i a and the release o f creat inine f rom muscles are all factors tha t we believe cou ld help contr ibute to this increase. With- ou t urinalysis, however , this is pure ly speculat ion.

In conclus ion , the overall picture for novice triathletes is tha t they f ind these short-sprint t r ia thlons physiological ly stressful. The responses are similar to those f o u n d in elite triathletes for t r ia thlons o f longer dura- t ion and we wou ld suggest, therefore, that the use o f the short t r ia th lon is an initial first step into the longer and more d e m a n d i n g ful l-course triathlon. We feel tha t more work needs to be unde r t aken with novice athletes especially in the area o f t r iathlons, which are current ly so popular .

Acknowledgements. We wish to thank Dr. Mark Hagreaves and Dr. John Carlson of the Footscray Institute of Technology for their comments on the revised manuscript and the Launceston Pa- thology Clinic for their analysis of the blood samples.

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Hematological and biochemical changes during a short triathlon competition in novice triathletes