Effect of 12 Weeks of Strenuous Physical Training on Hematological Changes

Transcription

1 MILITARY MEDICINE, 170, 7:590, 2005 Effect of 12 Weeks of Strenuous Physical Training on Hematological Changes Guarantor: LTC Satoshi Fujitsuka, MC GSDF Contributors: LTC Yuji Koike, MC GSDF* ; CPT Atsushi Isozaki, MC GSDF*; CPT Yozo Nomura, MC GSDF*; LTC Satoshi Fujitsuka, MC GSDF* It is well known that sports and physical exercise affect the hemoglobin (Hb) concentrations; however, the factors affecting the hematological changes after intense exercise are still not fully elucidated. In the present study, we examined the hematological and biochemical parameters of nine young male soldiers participating in a 12-week ranger training program. The platelet counts before the training showed a strong inverse correlation with the Hb concentrations after the training (r , p 0.01). Furthermore, the Hb concentrations of the subjects whose platelet counts were more than / L decreased significantly after the training (p 0.05). Our findings suggest that an association exists between high platelet counts even within the normal range before strenuous physical training and the risk of a subsequent decrease in the Hb concentrations. Introduction he impact of various sports and type of exercise on the T physiology of humans has been well discussed. It is well known that biochemical parameters such as creatine kinase (CK), lactate dehydrogenase (LD), and aspartate aminotransferase (AST) increase after intensive exercise. 1,2 These findings suggest that intensive exercise causes skeletal but not myocardial muscle damage. 3 In addition, hepatic damage 4 and hyponatremia 2 to some extent have also been reported to be caused by physical exercise. Furthermore, strenuous exercise is reported to affect immune functions, 5 including the immunoglobulin production ability 6 or T cell function. 7,8 Consistent with these findings, athletes or soldiers who participate in rigorous physical training sometimes tend to easily come down with viral infections, such as the common cold and herpes simplex infection. 8 Hematological changes such as decreases in the hemoglobin (Hb) concentrations and red blood cell (RBC) counts are often found to result from participation in impact sports, 9,10 intensive physical exercise, 11 and strenuous military training. 12 Recently, long-term sports anemia in Special Forces trainees was also reported. 13 These changes are suggested to be mainly caused by an iron deficiency, and a negative iron balance can thus be caused by intense physical exercise, 14 especially in women. 15 In addition, an increased gastrointestinal blood loss, 15 hematuria, 16 and intravascular hemolysis 17,18 are known to be caused by intensive exercise. In the present study, we examined the effects of a 12-week *Department of Pediatrics, Self-Defense Forces Central Hospital, Ikejiri, Setagaya, Tokyo, , Japan. Surgeon of the 4th Division, Ground Self-Defense Force, 5-12 Yamatomachi, Kasuga, , Japan. This manuscript was received for review in November The revised manuscript was accepted for publication in June Reprint & Copyright by Association of Military Surgeons of U.S., ranger training program, including 7 weeks of basic training and 5 weeks of field training on the hematological and biochemical changes in young soldiers, and also evaluated the relationship between the hematological parameters as well as the biochemical parameters in the subjects before and after undergoing this strenuous training program. Methods Subjects Nine subjects were selected who were healthy, well-trained male soldiers in the Japan Ground-Self Defense Force with an average age of years (range, years). Although six of the nine of the subjects had been smokers, all quit smoking during the training program. They did not take any medications or supplements. Their body weight was measured with a digital scale before and after the ranger training; however, no significant changes were observed before and after the training ( kg before vs kg after). Ranger Training The subjects participated in 7 weeks of basic ranger training followed by a subsequent 5 weeks of field training. The basic training mainly consisted of an enhancement of physical fitness, running and road marches with and without carrying loads. The field training consisted of continuous training in field areas for 1 to 4 days nine times during this program as Kosano et al. 3 described previously. For instance, the trainees moved approximately 50 km through a secluded place among the mountains, carrying 30 to 40 kg of equipment. Sleep was limited to about 3 hours and meals to approximately 600 kcal/day each. All subjects were examined by a physician at least three times (before, during, and after the ranger training course). Peripheral Blood Samples and Analysis Peripheral blood samples were obtained from the subjects before, during (at the completion of basic training and before the field training), and after the training. All samples were obtained at 7 a.m. before breakfast from the cubital vein. Informed consent was obtained from all subjects. The white blood cell (WBC) counts, RBC counts, Hb concentrations, mean corpuscular volume (MCV), and platelet counts in the blood samples were analyzed by an automated hematology analyzer (SE-9000, Sysmex, Kobe, Japan). To analyze the biochemical parameters, including AST, LD, CK, blood urea nitrogen (BUN), total protein (TP), albumin (Alb), total cholesterol (TC) and triglyceride (TG), the blood samples were allowed to clot at room temperature for 30 to 40 minutes and were centrifuged. Next the parameters in the sera were analyzed by a clinical chemistry analyzer (AU-800, Olympus, Tokyo, Japan). There was no evidence of hemolysis in any of the samples. 590

2 Effect of Physical Training on Hematological Changes Statistical Analysis A statistical analysis was performed using the StatView program (version 4.5) for Windows (Abacus Concepts, Berkeley, California). All data are expressed as the mean SD. The Mann- Whitney U test was used to compare any intergroup differences and the Wilcoxon s signed rank test was used to compare any differences between paired parameters. Spearman s rank correlation was used to examine the relationship between various parameters and the p value was examined by Fisher s Z exchange. Differences were considered to be significant when p Results Changes in the Hematological Parameters before and after the Training Program The Hb concentrations and RBC counts decreased g/dl to g/dl ( 12.2%) and / L to / L ( 11.6%), respectively, after the training program (p 0.01, Fig. 1). On the other hand, the platelet counts and MCV increased / L to / L and fl to fl, respectively, after the training program (p 0.01, Fig. 1). The WBC counts did not change significantly (6,044 1,699/ L before vs. 7,000 2,070/ L after). Changes in the Biochemical Parameters before and after the Training Program The levels of AST, LD, BUN, and TC increased after the training (p 0.01, Figs. 2 and 3). Although we did not analyze CK in the blood samples before the training, the CK levels also increased after the training (p 0.05, Fig. 2). The levels of TP and Alb decreased (p 0.01, Fig. 3); however, the TG levels did not change after the training (Fig. 3). 591 Factors before the Training Program Associated with the Subsequent Decrease in the Hb Concentrations or RBC Counts We examined the factors before the training in association with a decrease in either the Hb concentrations or RBC counts. Interestingly, among the parameters examined before the training, only the platelet counts showed a strong inverse correlation with the Hb concentrations during and after the training (r and 0.829, respectively, p 0.01 Fig. 4, A and B). Although the platelet counts before the training did not correlate with the RBC counts during the training (Fig. 4C), the platelet counts before the training also correlated with the RBC counts after the training (r 0.719, p 0.01, Fig. 4D). Effect of the Decrease in the Hb Concentrations on the Platelet Counts In addition to the above findings, to clarify the effect of the decrease in the Hb concentrations on the platelet counts before, during, and after the training, we divided the subjects into two groups according to their Hb concentrations after the training. One group consisted of three subjects with Hb concentrations of 14.0 g/dl after the training (Hi Hbs) and the other group consisted of six subjects with Hb concentrations 14.0 g/dl after the training (Lo Hbs). Accordingly, although the platelet counts in Hi Hbs did not change any more, the platelet counts in Lo Hbs increased significantly after the training (p 0.05, Fig. 5A). Furthermore, there were significant differences in the platelet counts between Hi Hbs and Lo Hbs, even before the training (p 0.05, Fig. 5A). However, no differences were observed between the groups regarding the Hb concentrations or RBC counts before the training (data not shown). Fig. 1. Hematological changes before, during, and after ranger training. Values are the mean SD from nine subjects. Hb, the normal range is g/dl; RBC, the normal range is / L; MCV, the normal range is fl; and Plt, the normal range is / L., p 0.01;, p 0.05.

3 592 Effect of Physical Training on Hematological Changes Fig. 2. Biochemical changes before, during, and after ranger training (1). Values are the mean SD from nine subjects. AST, the normal range is IU/L; LD, the normal range is IU/L; CK, the normal range is IU/L; and BUN, the normal range is 8 20 mg/dl., p 0.01;, p Fig. 3. Biochemical changes before, during, and after ranger training (2). Values are the mean SD from nine subjects. TP, the normal range is g/dl; Alb, the normal range is g/dl; TC, the normal range is mg/dl; and TG, the normal range is mg/dl., p 0.01;, p The Platelet Counts before the Training and the Decrease in the Hb Concentrations To further clarify the relationship between the platelet counts before the training and the subsequent decrease in the Hb concentrations, we also divided the subjects into two groups according to the platelet counts before the training. One group consisted of four subjects with platelet counts of / L before the training (Hi Plts) and the other group consisted of five subjects with the platelet counts / L before the training (Lo Plts). The Hb concentrations of the Hi Plts decreased significantly after the training (p 0.05, Fig. 5B), and significant differences were observed in the Hb concentrations during and after the training between the Hi Plts and Lo Plts (p 0.05, Fig. 5B). Fig. 4. Relationships between the platelet counts before ranger training and the hematological parameters during and after such training. The platelet counts inversely correlated strongly with the Hb concentrations during training (A), after training (B), and the RBC counts after training (D) but not during training (C). The data are based on the findings from nine subjects. Hb, the normal range is g/dl; and RBC, the normal range is / L. Discussion Either anemia or a decrease in the Hb concentrations is often observed in healthy individuals after various intensities of sports and physical exercise. 11,15 It is speculated that a negative iron balance is the main cause of hematological changes; however, the factors related to the pathophysiology before participating in physical exercise have not yet been fully elucidated. As far as we know, the present study is the first to demonstrate an association between the platelet counts before participating in a prolonged strenuous training program and the risk of a decrease in the Hb concentrations due to such exercise. One of the important causes of anemia or a decrease in the Hb concentrations due to physical exercise is iron deficiency. The

4 Effect of Physical Training on Hematological Changes 593 Fig. 5. Effects of both the decrease of Hb concentrations on the platelet counts and the high platelet counts before ranger training on the Hb concentrations. The platelet counts in the group (n 6) with the Hb concentrations 14.0 g/dl after training increased significantly (A). On the other hand, the Hb concentrations in the group (n 4) with platelet counts of / L before training decreased significantly (B). Values are the mean SD. Hb, the normal range is g/dl; and Plt, the normal range is / L., p cause of the iron deficiency is considered to be that exercise itself often leads to a negative iron balance. 15 Heme iron is an important dietary source of iron because it is more effectively absorbed than non-heme iron. 19 Therefore, it is well known that vegetarians, especially female athletes are at a relatively greater risk for iron deficiency attributable to physical exercise. 14 In addition to the iron deficiency, intravascular hemolysis 17 during exercise with intensive footstriking, 18 increased the gastrointestinal blood loss, 15 and hematuria 17 can occur during or after strenuous exercise and thus can also play important roles in a decrease in the Hb concentrations. In general, the elevation of AST, CK, and LD after intense physical training indicates skeletal muscle damage. 1,3 The elevation of LD is caused by hemolysis 20 as well. We did not examine the isoenzyme levels of LD in the subjects; the levels of LD after the training in Lo Hbs tend to be higher than those in Hi Hbs ( IU/L vs IU/L). This may be partly caused by the intravascular hemolysis during the training. 20 Although we did not estimate the ferokinetics of the subjects, the MCV did not decrease after the 12- week training program even in Lo Hbs. We speculate that in addition to the progression of iron deficiency, intravascular hemolysis is also considered to play an important role in the decrease in the Hb concentrations during and after prolonged strenuous exercise. Another effect of long-term strenuous exercise on hematological changes is an increase in the platelet counts. 10,11,21 One of the causes of the increased platelet counts after exercise is speculated to be a fresh release of platelets from the spleen, bone marrow, and lungs. 21 We herein showed that the platelet counts increased in Lo Hbs but not in Hi Hbs during and after the ranger training. Anemia is known to cause reactive thrombocytosis and increased levels of erythropoietin attributable to anemia may possibly stimulate the thrombopoiesis of bone marrow. 22,23 Interestingly, the platelet counts in patients with iron deficiency anemia whose platelet counts are / L as well as / L were reported to decrease after iron replacement therapy. 22 Therefore, our findings suggest that reactive thrombocytosis (although within the normal range) associated with the decline of the Hb concentrations is one of the major causes of the increase in the platelet counts after prolonged strenuous exercise. A circadian rhythm of the platelet counts has been reported in healthy individuals 24 and thus platelet counts are considered to be fundamentally stable in healthy individuals if obtained at the same time of day. Griesshammer et al. 25 reported that an elevated platelet count of / L on routine examination was considered to have diagnostic, prognostic, and therapeutic implications regarding tissue damage, infection, malignancy, and chronic inflammation; however, there have so far been few reports concerning platelet counts within the normal range in association with a pathophysiology of diseases. Thaulow et al. 26 demonstrated that the annual coronary heart disease and total mortality increased with increasing platelet counts within the normal range in healthy middle-aged men who were followed up for 13.5 years. They concluded that the platelet counts were a strong and independent predictor of coronary heart disease mortality. 26 We found platelet counts of / L, even when within the normal range, before the training, to be correlated with a subsequent decrease of Hb concentrations after the training. We speculate that high platelet counts before the training also represent reactive thrombocytosis within the normal range before the training. This phenomenon may have been caused by a subclinical iron deficiency or hemolysis (e.g., due to occult vascular damage) without any overt anemia in Hi Plts before participating in the training. This is a possible explanation as to why there was no significant difference in Hb concentrations before the training between Hi Plts and Lo Plts. Furthermore, along with progression of the pathophysiology, as described above, due to the strenuous exercise, it seems that the decrease in the Hb concentrations became more obvious in the Hi Plts than in the Lo Plts. In conclusion, our findings suggest that an association exists between platelet counts of / L before strenuous physical training and the risk of a subsequent decrease in the Hb concentrations. Kehat et al. 13 recommend a complete anemia workup when below normal hematological indices are found when participating in prolonged strenuous training. Although further studies are needed to establish the association because our study population was small, we also propose that serial hematological monitoring may thus be desirable for those with high platelet counts before such training, even if they are still within the normal range. References 1. Miles MP, Naukam RJ, Hackney AC, Clarkson PM: Blood leukocyte and glutamine fluctuations after eccentric exercise. Int J Sports Med 1999; 20: Warburton DE, Welsh RC, Haykowsky MJ, Taylor DA, Humen DP: Biochemical

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