- Email: [email protected]
Blood chemistry and immune cell changes during 1 week of intensive firefighting training
ARTICLE IN PRESS
Journal of Thermal Biology 29 (2004) 725–729 www.elsevier.com/locate/jtherbio
Blood chemistry and immune cell changes during 1 week of intensive firefighting training D.L. Smitha,, K. Dyerb, S.J. Petruzzelloc a
Skidmore College, Human Performance Laboratory, Exercise, Dance and Athletics, 815 North Broadway, Saratoga Springs, NY 12866, USA b Carle Medical Center, Urbana, IL, USA c University of Illinois, Champaign, IL, USA
Abstract Blood chemistry and immune cell parameters were examined in firefighters in a 1-week program of ‘‘live fire’’ training exercises. Blood samples were obtained at the beginning (AM) and end (PM) of each of the last 4 days of training. Analyses revealed significant time (AM-to-PM) effects for of the blood chemistry and immune variables along with significant leukocytosis over the 4 days of training. Despite the significant changes, these data suggest that serial days of supervised firefighting training do not appear to cause dangerous changes in blood chemistry or immunosuppression. r 2004 Elsevier Ltd. All rights reserved. Keywords: Blood chemistry; Immune cell count; Leukocytosis; Physical stressors; Live-fire training
1. Introduction It is known that components of blood chemistry (e.g., glucose, creatinine, sodium) and the immune system (e.g., WBCs, lymphocytes, monocytes) are affected by a variety of physiological and psychological stressors. Exercise causes an alteration in blood chemistry and immune cell count that is dependent on the intensity and duration of the exercise (Gabriel et al., 1992; Mitchell et al., 2002). Hyperthermia is another physical stressor that is known to cause hormonal and immunological changes (Brenner et al., 1995; Cross et al., 1996; Downing et al., 1988; Pedersen et al., 1997). Exercise performed in a hot environment represents a combination of stressors that may have an additive effect on the immune systems and on blood chemistry (Brenner et al., 1998; Cross Corresponding author. Tel.: +1-518-580-5389; fax: +1518580-5396 E-mail address: [email protected] (D.L. Smith).
et al., 1996; Gaffin and Hubbard, 2001; Mitchell et al., 2002). Firefighting involves strenuous physical activity that is performed in hot and hostile environments. Firefighters experience high levels of physical exertion and are subject to significant psychological stress (Smith et al., 2001a,b). Thus, firefighting leads to significant cardiovascular and thermal strain, and may lead to dehydration due to profuse sweating (Manning and Griggs, 1983; Smith et al., 1997, 2001a,b). Therefore, it is not surprising that initial studies have reported that firefighting activities lead to acute changes in blood chemistry and immune cell counts (Smith et al., 2001a,b). To our knowledge, the effect of repeated days of firefighting activity on blood chemistry and immune cell counts has not been investigated. It is important to characterize these responses to serial days of firefighting because firefighters routinely enroll in training programs that involve several days of intensive, live-fire training
0306-4565/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtherbio.2004.08.046
ARTICLE IN PRESS 726
D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
and because repeated days of strenuous activity mimics the situation that emergency workers might face in the event of a large scale disaster. The purpose of this study, therefore, was to describe changes in blood chemistry and in immune cell counts in a group of firefighters (N ¼ 16) undergoing a 1-week intensive training course at the State Fire Academy.
2. Materials and methods Firefighters (N ¼ 16) undergoing a 1-week intensive training program (Breathing Apparatus Specialist; Smoke Divers) served as participants in this study. All participants were informed of the requirements of the study and provided written informed consent. Participants were career firefighters who had received a medical examination within the past 2 years and were medically cleared for active duty. The training program included subject recruiting and classroom activities on the first day (day 0) of class and ‘‘live fire’’ training exercises in specially designed buildings during the last four days. During the training program participants worked in real and simulated fire conditions while performing functions where self-contained breathing apparatus was essential. The participants were also exposed to self-rescue and firefighter rescue techniques, as well as procedures for effective search and rescue. All training activities were closely supervised and participants were mandated to drink large volumes of water. Measures of nude body weight were obtained at the beginning and end of each of days 1–4. Blood samples were obtained from the antecubital vein via venipuncture at the beginning (AM) and end (PM) of each of the last 4 days of training (days 1–4). All blood samples were obtained following 15 min of supine rest. Blood samples for leukocyte counts were collected into vacutainer tubes containing K3-EDTA and analyzed using radio frequency and direct current. Samples for blood chemistry testing were collected in SST vacutainer tubes containing a gel separator. The specimens were centrifuged at 2800 rpm for 10 min and the serum analyzed using standard methodology. Changes in blood volume were calculated from changes in hemoglobin and hematocrit using the equation of Strauss (Greenleaf et al., 1979). Blood chemistry values and leukocyte counts were corrected for changes in blood volume. Descriptive statistics are reported as mean plus or minus standard deviation. Repeated measures analyses of variance (RMANOVA) were employed to determine significant main effects for time (AM, PM) and days (1–4), with a significance level of po0.05 considered accpetable.
3. Results Nude body weight decreased significantly from AM to PM (1.0–1.5 kg) each day, representing dehydration of approximately 1.0–1.7%. There was, however, no significant change in body weight across days. Furthermore, there was no significant difference among the morning body weight values across days (0.25 kg decrease from day 1 to 4). Changes in the blood chemistry variables (corrected for changes in plasma volume) are presented in Table 1. RMANOVA revealed a significant time effect for 4 of the 9 variables. There was also a significant day effect, indicative of changes from day 1 to 4, for all of the 9 blood chemistry variables. Changes in leukocyte counts (corrected for changes in plasma volume) are shown in Table 2. RMANOVA revealed a significant time effect for total leukocytes and each of the subsets with cell count increasing from AM to PM. Only total leukocytes, lymphocytes and monocytes had a significant day main effect, seemingly reflecting greater total leukocytes and lymphocytes on days 3 and 4 and greater monocytes on Day 2. Finally, a significant day Time interaction occurred for total leukocytes, neutrophils, and lymphocytes, reflecting the greatest AM-to-PM increase in each on day 3 followed by the smallest AM-to-PM increase on day 4.
4. Discussion The primary findings of this investigation were that (a) firefighting activity leads to acute changes in many blood chemistry variables and an overall leukocytosis (after correcting for plasma volume changes), and (b) that repeated days of firefighting activity lead to significant alterations in blood chemistry and immune cell counts. The magnitude of the alteration in blood chemistry values and blood cell counts was greater within days (AM-to-PM) than it was from day 1 to day 4. It has long been known that high intensity exercise leads to alterations in blood chemistry (Van Beaumont, 1973). Although there were significant changes in all of the 9 blood chemistry variables over the course of the four days of training, none of the values reached clinically significant levels in this group of relatively healthy firefighters. There was a significant increase of circulating leukocytes from AM-to-PM, with the number of leukocytes increasing by approximately 100% within each day. The magnitude of exercise-induced leukocytosis is dependent on intensity of exercise, with increases of 20–50% being common for moderate-intensity exercise and increases of 200–300% being reported during high intensity exercise (Mackinnon, 1999; Plowman and Smith, 2003). The increase in circulating
Table 1 Blood chemistry changes from AM-to-PM over 4 days of training Variable
Time
Stats
M Calcium (mg/dl)
SD
9.86 0.17 10.29 0.46 99.15 32.2 84.18 9.34 14.77 2.71 18.27 3.52 1.15 0.13 1.30 0.20 140.77 1.64 143.81 8.79 4.20 0.24 4.16 0.27 105.23 1.92 106.80 5.99 28.11 1.82 27.77 3.92 11.63 1.31 13.32 2.26
M
Day 3 SD
M
Day 4 SD
M
Day
Time
DT
SD
9.96 0.44 10.01 0.64 10.46 0.99 F(1.7,20.7)=6.90 p=.007 10.36 0.60 10.59 0.79 10.96 0.82 108.11 37.97 109.17 38.30 115.81 38.78 F(2.1,25.7)=3.75 p=.035 85.76 12.74 89.61 16.3 94.22 15.93 15.20 4.14 17.31 5.61 19.07 5.33 F(1.7,20.6)=9.40 p=.002 19.47 5.27 21.36 6.12 21.04 4.76 1.14 0.18 1.16 0.17 1.24 0.19 F(2.1,24.7)=11.17 po.001 1.35 0.22 1.42 0.25 1.46 0.21 142.44 8.75 144.25 10.41 151.61 14.05 F(1.8,21.8)=5.90 p=.011 142.85 10.78 145.00 11.03 150.81 13.43 4.14 0.21 4.34 0.48 4.49 0.64 F(2.1,24.9)=4.37 p=.023 4.30 0.46 4.31 0.64 4.58 0.58 107.74 6.50 110.66 7.82 115.15 10.40 F(1.9,22.8)=9.44 p=.001 107.86 8.18 110.25 8.09 116.31 10.50 29.05 1.65 28.27 2.82 30.34 3.25 F(2.2,26.4)=5.87 p=.006 28.21 2.74 27.64 3.81 30.48 3.82 9.79 2.02 9.66 1.04 10.62 1.58 F(2.2,26.7)=32.05 po.001 10.80 1.78 11.07 2.10 7.90 1.50
F(1,12)=34.13 po.001 F(1.12)=4.89 po.001 F(1.12)=59.74 po.001 F(1.12)=44.72 po.001
F(2.2,26.8)=15.24 po.001
ARTICLE IN PRESS
AM PM Glucose (mg/dl) AM PM Blood urea N (mg/dl) AM PM Creatinine (mg/dl) AM PM Sodium (mmol/l) AM PM Potassium (mmol/l) AM PM Chloride (mmol/l) AM PM Carbon dioxide (mmol/l) AM PM Anion gap AM PM
Day 2
D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
Day 1
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ARTICLE IN PRESS
F(1,12)=6.16 po.001
F(1,12)=46.37 po.001 F(2.5,29.5)=6.73 p=.002
F(1,12)=1317 po.001
F(1,12)=33.29 po.001
F(2.2,25.8)=5.35 p=.010 F(1,12)=163.90 po.001
1.50 1.55 1.28 1.50 0.64 0.51 0.19 0.19 0.13 0.12 0.02 0.02 6.56 9.49 3.86 6.30 1.94 2.23 0.52 0.78 0.21 0.17 0.03 0.03 0.96 2.23 0.89 2.21 0.44 0.80 0.12 0.23 0.11 0.11 0.01 0.02 Basophils ( 103/ml)
Eosinophils ( 103/ml)
Monocytes ( 103/ml)
Lymphocytes ( 103/ml)
Neutrophils ( 103/ml)
3
WBC ( 10 /ml)
AM PM AM PM AM PM AM PM AM PM AM PM
5.74 10.16 3.58 7.13 1.56 2.31 0.42 0.73 0.16 0.17 0.02 0.03
1.29 1.59 1.14 1.59 0.46 0.73 0.13 0.20 0.11 0.13 0.01 0.01
5.83 9.57 3.46 6.57 1.68 2.04 0.48 0.80 0.19 0.12 0.02 0.03
1.10 1.56 0.97 1.32 0.40 0.65 0.17 0.16 0.13 0.07 0.01 0.02
5.80 10.89 3.44 7.49 1.69 2.36 0.45 0.85 0.19 0.16 0.03 0.03
SD M M M
SD
Day 2 Day 1
SD
M
SD
F(1.8,21.9)=3.66 p=.046
F(2.0,24.1)=10.40 p=.001 F(2.7,32.8)=3.15 p=.042
F(1,12)=227.11 po.001
DT Time Day Day 3
Day 4
Stats Time Variable
Table 2 Leukocyte changes from AM-to-PM over 4 days of training
F(2.3,28.0)=4.00 p=.024
D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
728
leukocytes following exercise is often attributed to the action of the sympathoadrenal-mediated stress hormones; however, there is also evidence that increased body temperature influences the magnitude of stress hormone release. Rhind et al. (1999) performed an experiment in which participants performed two exercise trials, one in cold water and one in hot water. Body temperature increased during the hot-water trial but was unchanged during the cold-water trial. In this experiment there was a significantly greater level of circulating epinephrine, norepinephrine and cortisol in the trial in which body temperature increased. Likewise, there was a greater increase in circulating leukocytes (and lymphocytes) in the hot-water trial. Repeated bouts of exercise within a day (intermittent) have been shown to lead to greater increase in leukocyte number than a single bout of exercise (Brenner et al., 1996). Furthermore, these authors reported that the greater increase in cell counts during the second bout of exercise was exacerbated when the exercise was performed in the heat. Nielsen et al. (1996) investigated the effects of repeated bouts (subsequent days) of maximal exercise (6-min maximal ergometer rowing) on blood cell counts and reported that the maximal effort resulted in a two-fold (100%) increase in leukocyte number on day one and a three-fold increase in leukocyte number on day two.
5. Summary The results from this study suggest that there are significant changes in blood chemistry that occur as a result of a single day of firefighting training, and furthermore, most of the blood variables were significantly disrupted over the course of the 4 day training period (although not approaching clinically significant levels). Firefighting activities resulted in a leukocytosis that was evident from the beginning of the day to the end of the day, and over the course of the 4 days of training. Despite the significant changes that were detected, none of the reported variables fell outside of the normal range for healthy young subjects. These data suggest that healthy young men can engage in serial days of supervised firefighting training without causing dangerous changes in blood chemistry or evidence of immunosuppression.
Acknowledgements The assistance and cooperation of the University of Illinois Fire Service Institute instructors is gratefully acknowledged.
ARTICLE IN PRESS D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
References Brenner, I.K.M., Shek, P.N., Shephard, R.J., 1995. Heat exposure and immune function: potential contribution to the exercise response. Exercise Immunol. Rev. 1, 49–80. Brenner, I.K.M., Shek, P.N., Shephard, R.J., 1998. Stress hormones and the immunological responses to heat and exercise. Int. J. Sports Med. 19, 130–143. Cross, M.C., Radomski, M.W., Vanhelder, J.W.P., Rhind, S.G., Shephard, R.J., 1996. Endurance exercise with and without a thermal clamp: effects on leukocytes and leukocyte subsets. J. Appl. Physiol. 81, 822–829. Downing, J.F., Martinez-Valdez, H., Elizondo, R.S., Walker, E.B., Taylor, M.W., 1988. Hyperthermia in humans enhances interferon-g synthesis and alters the peripheral lymphocyte population. J. Interferon Res. 8, 143–150. Gabriel, H., Schwarz, L., Steffens, G., Kinderman, W., 1992. Immunoregulatory hormones, circulating leukocyte and lymphocyte subpopulations before and after endurance exercise of different intensities. Int. J. Sports Med. 13, 359–366. Gaffin, S.L., Hubbard, R.W., 2001. Pathophysiology of heatstroke. In Pandolf, K.B., Burr, R.E. (Eds.), Medical Aspects of Harsh Environments, Office of the Surgeon General. Greenleaf, J.E., Convertino, V.A., Mangseth, G.R., 1979. Plasma volume changes during stressing man: osmolality and red cell volume. J. Appl. Physiol. 47, 1031–1038. Mackinnon, L.T., 1999. Advances in exercise immunology. Human Kinetics, Champain, IL.
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Manning, J., Griggs, T., 1983. Heart rates of firefighters using light and heavy breathing equipment: similar near maximal exertion in response to multiple work load conditions. J. Occup. Med. 25, 215–218. Mitchell, J.B., Dugas, J.P., McFarlin, B.K., Nelson, M.J., 2002. Effect of exercise, heat stress, and hydration on immune cell number and function. Med. Sci. Sports Exercise 34 (12), 1941–1950. Nielsen, H.B., Secher, N.H., Christensen, N.J., Pedersen, B.K., 1996. Lymphocytes and NK cell activity during repeated bouts of maximal exercise. Am. J. Physiol. 271, 222–227. Plowman, S.A., Smith, D.L., 2003. Exercise Physiology: for Health, Fitness, and Performance, Second ed. Benjamin Cummings, San Francisco, CA. Rhind, S.G., Gannon, G.A., Shek, P.N., et al., 1999. Contribution of exertional hyperthermia to sympathoadrenal-mediated lymphocyte subset redistribution. J. Appl. Physiol. 87, 1178–1185. Smith, D.L., Petruzzello, S.J., Kramer, J.M., Misner, J.E., 1997. The effects of different thermal environments on the physiological and psychological responses of firefighters to a training drill. Ergonomics 40, 500–510. Smith, D.L., Petruzzello, M.A., Chludzinski, J.J.R., Woods, J.A., 2001a. Effects of strenuous live-fire fire fighting drills on hematological, blood chemistry, and psychological measures. J. Thermal Biol. 26 (4-5), 375–380. Smith, D.L., Petruzzello, S.J., Manning, T.S., 2001b. The effect of strenuous live-fire drills on cardiovascular and psychological responses of recruit firefighters. Ergonomics 44 (3), 244–254.
Journal of Thermal Biology 29 (2004) 725–729 www.elsevier.com/locate/jtherbio
Blood chemistry and immune cell changes during 1 week of intensive firefighting training D.L. Smitha,, K. Dyerb, S.J. Petruzzelloc a
Skidmore College, Human Performance Laboratory, Exercise, Dance and Athletics, 815 North Broadway, Saratoga Springs, NY 12866, USA b Carle Medical Center, Urbana, IL, USA c University of Illinois, Champaign, IL, USA
Abstract Blood chemistry and immune cell parameters were examined in firefighters in a 1-week program of ‘‘live fire’’ training exercises. Blood samples were obtained at the beginning (AM) and end (PM) of each of the last 4 days of training. Analyses revealed significant time (AM-to-PM) effects for of the blood chemistry and immune variables along with significant leukocytosis over the 4 days of training. Despite the significant changes, these data suggest that serial days of supervised firefighting training do not appear to cause dangerous changes in blood chemistry or immunosuppression. r 2004 Elsevier Ltd. All rights reserved. Keywords: Blood chemistry; Immune cell count; Leukocytosis; Physical stressors; Live-fire training
1. Introduction It is known that components of blood chemistry (e.g., glucose, creatinine, sodium) and the immune system (e.g., WBCs, lymphocytes, monocytes) are affected by a variety of physiological and psychological stressors. Exercise causes an alteration in blood chemistry and immune cell count that is dependent on the intensity and duration of the exercise (Gabriel et al., 1992; Mitchell et al., 2002). Hyperthermia is another physical stressor that is known to cause hormonal and immunological changes (Brenner et al., 1995; Cross et al., 1996; Downing et al., 1988; Pedersen et al., 1997). Exercise performed in a hot environment represents a combination of stressors that may have an additive effect on the immune systems and on blood chemistry (Brenner et al., 1998; Cross Corresponding author. Tel.: +1-518-580-5389; fax: +1518580-5396 E-mail address: [email protected] (D.L. Smith).
et al., 1996; Gaffin and Hubbard, 2001; Mitchell et al., 2002). Firefighting involves strenuous physical activity that is performed in hot and hostile environments. Firefighters experience high levels of physical exertion and are subject to significant psychological stress (Smith et al., 2001a,b). Thus, firefighting leads to significant cardiovascular and thermal strain, and may lead to dehydration due to profuse sweating (Manning and Griggs, 1983; Smith et al., 1997, 2001a,b). Therefore, it is not surprising that initial studies have reported that firefighting activities lead to acute changes in blood chemistry and immune cell counts (Smith et al., 2001a,b). To our knowledge, the effect of repeated days of firefighting activity on blood chemistry and immune cell counts has not been investigated. It is important to characterize these responses to serial days of firefighting because firefighters routinely enroll in training programs that involve several days of intensive, live-fire training
0306-4565/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtherbio.2004.08.046
ARTICLE IN PRESS 726
D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
and because repeated days of strenuous activity mimics the situation that emergency workers might face in the event of a large scale disaster. The purpose of this study, therefore, was to describe changes in blood chemistry and in immune cell counts in a group of firefighters (N ¼ 16) undergoing a 1-week intensive training course at the State Fire Academy.
2. Materials and methods Firefighters (N ¼ 16) undergoing a 1-week intensive training program (Breathing Apparatus Specialist; Smoke Divers) served as participants in this study. All participants were informed of the requirements of the study and provided written informed consent. Participants were career firefighters who had received a medical examination within the past 2 years and were medically cleared for active duty. The training program included subject recruiting and classroom activities on the first day (day 0) of class and ‘‘live fire’’ training exercises in specially designed buildings during the last four days. During the training program participants worked in real and simulated fire conditions while performing functions where self-contained breathing apparatus was essential. The participants were also exposed to self-rescue and firefighter rescue techniques, as well as procedures for effective search and rescue. All training activities were closely supervised and participants were mandated to drink large volumes of water. Measures of nude body weight were obtained at the beginning and end of each of days 1–4. Blood samples were obtained from the antecubital vein via venipuncture at the beginning (AM) and end (PM) of each of the last 4 days of training (days 1–4). All blood samples were obtained following 15 min of supine rest. Blood samples for leukocyte counts were collected into vacutainer tubes containing K3-EDTA and analyzed using radio frequency and direct current. Samples for blood chemistry testing were collected in SST vacutainer tubes containing a gel separator. The specimens were centrifuged at 2800 rpm for 10 min and the serum analyzed using standard methodology. Changes in blood volume were calculated from changes in hemoglobin and hematocrit using the equation of Strauss (Greenleaf et al., 1979). Blood chemistry values and leukocyte counts were corrected for changes in blood volume. Descriptive statistics are reported as mean plus or minus standard deviation. Repeated measures analyses of variance (RMANOVA) were employed to determine significant main effects for time (AM, PM) and days (1–4), with a significance level of po0.05 considered accpetable.
3. Results Nude body weight decreased significantly from AM to PM (1.0–1.5 kg) each day, representing dehydration of approximately 1.0–1.7%. There was, however, no significant change in body weight across days. Furthermore, there was no significant difference among the morning body weight values across days (0.25 kg decrease from day 1 to 4). Changes in the blood chemistry variables (corrected for changes in plasma volume) are presented in Table 1. RMANOVA revealed a significant time effect for 4 of the 9 variables. There was also a significant day effect, indicative of changes from day 1 to 4, for all of the 9 blood chemistry variables. Changes in leukocyte counts (corrected for changes in plasma volume) are shown in Table 2. RMANOVA revealed a significant time effect for total leukocytes and each of the subsets with cell count increasing from AM to PM. Only total leukocytes, lymphocytes and monocytes had a significant day main effect, seemingly reflecting greater total leukocytes and lymphocytes on days 3 and 4 and greater monocytes on Day 2. Finally, a significant day Time interaction occurred for total leukocytes, neutrophils, and lymphocytes, reflecting the greatest AM-to-PM increase in each on day 3 followed by the smallest AM-to-PM increase on day 4.
4. Discussion The primary findings of this investigation were that (a) firefighting activity leads to acute changes in many blood chemistry variables and an overall leukocytosis (after correcting for plasma volume changes), and (b) that repeated days of firefighting activity lead to significant alterations in blood chemistry and immune cell counts. The magnitude of the alteration in blood chemistry values and blood cell counts was greater within days (AM-to-PM) than it was from day 1 to day 4. It has long been known that high intensity exercise leads to alterations in blood chemistry (Van Beaumont, 1973). Although there were significant changes in all of the 9 blood chemistry variables over the course of the four days of training, none of the values reached clinically significant levels in this group of relatively healthy firefighters. There was a significant increase of circulating leukocytes from AM-to-PM, with the number of leukocytes increasing by approximately 100% within each day. The magnitude of exercise-induced leukocytosis is dependent on intensity of exercise, with increases of 20–50% being common for moderate-intensity exercise and increases of 200–300% being reported during high intensity exercise (Mackinnon, 1999; Plowman and Smith, 2003). The increase in circulating
Table 1 Blood chemistry changes from AM-to-PM over 4 days of training Variable
Time
Stats
M Calcium (mg/dl)
SD
9.86 0.17 10.29 0.46 99.15 32.2 84.18 9.34 14.77 2.71 18.27 3.52 1.15 0.13 1.30 0.20 140.77 1.64 143.81 8.79 4.20 0.24 4.16 0.27 105.23 1.92 106.80 5.99 28.11 1.82 27.77 3.92 11.63 1.31 13.32 2.26
M
Day 3 SD
M
Day 4 SD
M
Day
Time
DT
SD
9.96 0.44 10.01 0.64 10.46 0.99 F(1.7,20.7)=6.90 p=.007 10.36 0.60 10.59 0.79 10.96 0.82 108.11 37.97 109.17 38.30 115.81 38.78 F(2.1,25.7)=3.75 p=.035 85.76 12.74 89.61 16.3 94.22 15.93 15.20 4.14 17.31 5.61 19.07 5.33 F(1.7,20.6)=9.40 p=.002 19.47 5.27 21.36 6.12 21.04 4.76 1.14 0.18 1.16 0.17 1.24 0.19 F(2.1,24.7)=11.17 po.001 1.35 0.22 1.42 0.25 1.46 0.21 142.44 8.75 144.25 10.41 151.61 14.05 F(1.8,21.8)=5.90 p=.011 142.85 10.78 145.00 11.03 150.81 13.43 4.14 0.21 4.34 0.48 4.49 0.64 F(2.1,24.9)=4.37 p=.023 4.30 0.46 4.31 0.64 4.58 0.58 107.74 6.50 110.66 7.82 115.15 10.40 F(1.9,22.8)=9.44 p=.001 107.86 8.18 110.25 8.09 116.31 10.50 29.05 1.65 28.27 2.82 30.34 3.25 F(2.2,26.4)=5.87 p=.006 28.21 2.74 27.64 3.81 30.48 3.82 9.79 2.02 9.66 1.04 10.62 1.58 F(2.2,26.7)=32.05 po.001 10.80 1.78 11.07 2.10 7.90 1.50
F(1,12)=34.13 po.001 F(1.12)=4.89 po.001 F(1.12)=59.74 po.001 F(1.12)=44.72 po.001
F(2.2,26.8)=15.24 po.001
ARTICLE IN PRESS
AM PM Glucose (mg/dl) AM PM Blood urea N (mg/dl) AM PM Creatinine (mg/dl) AM PM Sodium (mmol/l) AM PM Potassium (mmol/l) AM PM Chloride (mmol/l) AM PM Carbon dioxide (mmol/l) AM PM Anion gap AM PM
Day 2
D.L. Smith et al. / Journal of Thermal Biology 29 (2004) 725–729
Day 1
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ARTICLE IN PRESS
F(1,12)=6.16 po.001
F(1,12)=46.37 po.001 F(2.5,29.5)=6.73 p=.002
F(1,12)=1317 po.001
F(1,12)=33.29 po.001
F(2.2,25.8)=5.35 p=.010 F(1,12)=163.90 po.001
1.50 1.55 1.28 1.50 0.64 0.51 0.19 0.19 0.13 0.12 0.02 0.02 6.56 9.49 3.86 6.30 1.94 2.23 0.52 0.78 0.21 0.17 0.03 0.03 0.96 2.23 0.89 2.21 0.44 0.80 0.12 0.23 0.11 0.11 0.01 0.02 Basophils ( 103/ml)
Eosinophils ( 103/ml)
Monocytes ( 103/ml)
Lymphocytes ( 103/ml)
Neutrophils ( 103/ml)
3
WBC ( 10 /ml)
AM PM AM PM AM PM AM PM AM PM AM PM
5.74 10.16 3.58 7.13 1.56 2.31 0.42 0.73 0.16 0.17 0.02 0.03
1.29 1.59 1.14 1.59 0.46 0.73 0.13 0.20 0.11 0.13 0.01 0.01
5.83 9.57 3.46 6.57 1.68 2.04 0.48 0.80 0.19 0.12 0.02 0.03
1.10 1.56 0.97 1.32 0.40 0.65 0.17 0.16 0.13 0.07 0.01 0.02
5.80 10.89 3.44 7.49 1.69 2.36 0.45 0.85 0.19 0.16 0.03 0.03
SD M M M
SD
Day 2 Day 1
SD
M
SD
F(1.8,21.9)=3.66 p=.046
F(2.0,24.1)=10.40 p=.001 F(2.7,32.8)=3.15 p=.042
F(1,12)=227.11 po.001
DT Time Day Day 3
Day 4
Stats Time Variable
Table 2 Leukocyte changes from AM-to-PM over 4 days of training
F(2.3,28.0)=4.00 p=.024
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leukocytes following exercise is often attributed to the action of the sympathoadrenal-mediated stress hormones; however, there is also evidence that increased body temperature influences the magnitude of stress hormone release. Rhind et al. (1999) performed an experiment in which participants performed two exercise trials, one in cold water and one in hot water. Body temperature increased during the hot-water trial but was unchanged during the cold-water trial. In this experiment there was a significantly greater level of circulating epinephrine, norepinephrine and cortisol in the trial in which body temperature increased. Likewise, there was a greater increase in circulating leukocytes (and lymphocytes) in the hot-water trial. Repeated bouts of exercise within a day (intermittent) have been shown to lead to greater increase in leukocyte number than a single bout of exercise (Brenner et al., 1996). Furthermore, these authors reported that the greater increase in cell counts during the second bout of exercise was exacerbated when the exercise was performed in the heat. Nielsen et al. (1996) investigated the effects of repeated bouts (subsequent days) of maximal exercise (6-min maximal ergometer rowing) on blood cell counts and reported that the maximal effort resulted in a two-fold (100%) increase in leukocyte number on day one and a three-fold increase in leukocyte number on day two.
5. Summary The results from this study suggest that there are significant changes in blood chemistry that occur as a result of a single day of firefighting training, and furthermore, most of the blood variables were significantly disrupted over the course of the 4 day training period (although not approaching clinically significant levels). Firefighting activities resulted in a leukocytosis that was evident from the beginning of the day to the end of the day, and over the course of the 4 days of training. Despite the significant changes that were detected, none of the reported variables fell outside of the normal range for healthy young subjects. These data suggest that healthy young men can engage in serial days of supervised firefighting training without causing dangerous changes in blood chemistry or evidence of immunosuppression.
Acknowledgements The assistance and cooperation of the University of Illinois Fire Service Institute instructors is gratefully acknowledged.
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