significantly different from pre-exercise value in the gymnasts group only

Table 1. Changes in the cellular components of the immune system. WBC and lymphocyte

Table 2. Immunoglobulin levels pre-exercise, immediately post-exercise among gymnasts (46).

subpopulations (cells/µl) following exercise in gymnasts and untrained girls (46).

2 to 4 hours post-exercise (42). This leukocyte trafficking reflect recruitment into the circulation of neutrophils and could be related to hemodynamic changes as increased cardiac output, hyperthermia or could reflect changes in circulating stress hormones, particularly epinephrine and cortisol, released during exercise (42). Resting leukocyte number is generally normal in athletes, although long periods of high-volume training may be associated with long lasting suppression of circulating cell numbers, which may persist low over weeks (43). This may be attributed to migration of leukocytes out of the circulation to possible damaged skeletal muscle (44).

Disproportionate changes in lymphocyte subsets occur during exercise. Usually, during prolonged exercise the NK and CD8 T- cells increase far more than B cells and CD4 T- cells counts (40). Significant decline in the CD4:CD8 ratio was reported after 60 min of treadmill running. Although neutrophil counts may remain elevated for several hours after exercise cessation, lymphocyte number may decline bellow baseline values for up to 6 hours post exercise (7). Following vigorous exercise it was reported a transient fall of circulating natural killer ( NK) cell count (45).

In summary, exercise increases neutrophil numbers and may reflect an appropriate response to exercise-induced stress rather than an impaired immunocompromised state. In contrast, the post-exercise decrease in the absolute lymphocyte counts, the NK decrease and the inversion of the CD4 to CD8 ratio, could indicate immunosuppresion.

It is remarkable that no significant changes were reported in B-cell circulating lymphocytes and only local salivary IgA reduction was shown following intense, prolonged exercise. The relationship between the leukocyte dynamics and the clinical implications is still unclear.

## **4. Immunological studies – Our experience**

Scant information exists on exercise-induced changes in the immune system among children. We investigated the effect of aerobic exercise on several aspects of cellular and humoral functions among 10-12 year-old highly trained female gymnasts and untrained girls (46). All girls were pre-pubertal. Venous blood samples were drawn before, immediately after and 24 h following 20 min of treadmill running (heart rate 170-180 beats.min-1). White blood cells' number rose significantly following exercise and remained elevated for 24 h. The increase in leukocyte number was due to an increase in granulocytes as well as an increase in lymphocytes and monocytes. While neutrophil count returned to basal values after 24 h, lymphocytes and monocytes number remained elevated 24 h following exercise. Exercise resulted in a significant elevation of T cell lymphocytes, T helpers, T suppressors and natural killer cells. All values returned to normal after 24 h. There were no changes in B cell lymphocytes following exercise (Table 1). Exercise had no effect on serum immunoglobulin's and sub-types of IgG {IgG1, IgG2, IgG3 and IgG4} (Table 2). No differences were observed between gymnasts and untrained girls (46). The changes observed were similar to those found in adults (40).

Our laboratory for leukocyte functions focused within the last 30 years on granulocyte functions and dysfunctions in healthy subjects and in patients suffering from recurrent, severe, opportunistic infections. For the last 15 years, our group focused on neutrophil functions following a single bout of submaximal aerobic exercise (47-50). Neutrophil functions as chemotaxis, oxidative burst, and bactericidal activity were unaffected immediately post-exercise, however neutrophil chemotactic activity was found significantly decreased 24 h after the cessation of the exercise (Table 3) (47).


\* significantly different from pre-exercise value in both groups

148 An International Perspective on Topics in Sports Medicine and Sports Injury

2 to 4 hours post-exercise (42). This leukocyte trafficking reflect recruitment into the circulation of neutrophils and could be related to hemodynamic changes as increased cardiac output, hyperthermia or could reflect changes in circulating stress hormones, particularly epinephrine and cortisol, released during exercise (42). Resting leukocyte number is generally normal in athletes, although long periods of high-volume training may be associated with long lasting suppression of circulating cell numbers, which may persist low over weeks (43). This may be attributed to migration of leukocytes out of the

Disproportionate changes in lymphocyte subsets occur during exercise. Usually, during prolonged exercise the NK and CD8 T- cells increase far more than B cells and CD4 T- cells counts (40). Significant decline in the CD4:CD8 ratio was reported after 60 min of treadmill running. Although neutrophil counts may remain elevated for several hours after exercise cessation, lymphocyte number may decline bellow baseline values for up to 6 hours post exercise (7). Following vigorous exercise it was reported a transient fall of circulating natural

In summary, exercise increases neutrophil numbers and may reflect an appropriate response to exercise-induced stress rather than an impaired immunocompromised state. In contrast, the post-exercise decrease in the absolute lymphocyte counts, the NK decrease and the

It is remarkable that no significant changes were reported in B-cell circulating lymphocytes and only local salivary IgA reduction was shown following intense, prolonged exercise. The relationship between the leukocyte dynamics and the clinical

Scant information exists on exercise-induced changes in the immune system among children. We investigated the effect of aerobic exercise on several aspects of cellular and humoral functions among 10-12 year-old highly trained female gymnasts and untrained girls (46). All girls were pre-pubertal. Venous blood samples were drawn before, immediately after and 24 h following 20 min of treadmill running (heart rate 170-180 beats.min-1). White blood cells' number rose significantly following exercise and remained elevated for 24 h. The increase in leukocyte number was due to an increase in granulocytes as well as an increase in lymphocytes and monocytes. While neutrophil count returned to basal values after 24 h, lymphocytes and monocytes number remained elevated 24 h following exercise. Exercise resulted in a significant elevation of T cell lymphocytes, T helpers, T suppressors and natural killer cells. All values returned to normal after 24 h. There were no changes in B cell lymphocytes following exercise (Table 1). Exercise had no effect on serum immunoglobulin's and sub-types of IgG {IgG1, IgG2, IgG3 and IgG4} (Table 2). No differences were observed between gymnasts and untrained girls (46). The changes

Our laboratory for leukocyte functions focused within the last 30 years on granulocyte functions and dysfunctions in healthy subjects and in patients suffering from recurrent, severe, opportunistic infections. For the last 15 years, our group focused on neutrophil functions following a single bout of submaximal aerobic exercise (47-50). Neutrophil

inversion of the CD4 to CD8 ratio, could indicate immunosuppresion.

circulation to possible damaged skeletal muscle (44).

**4. Immunological studies – Our experience** 

observed were similar to those found in adults (40).

killer ( NK) cell count (45).

implications is still unclear.
