The association
of the blood lymphocytes to neutrophils ratio with overtraining in endurance athletes
By Kaori Matsuo, Mayumi Kubota, Hiroshi Sasaki, Jiro Toyooka, Ryoichi Nagatomi
AUTHORS
Kaori Matsuo, PhD,
is an assistant professor at the Department of Medicine and Science in Sports and Exercise, Tohoku University Graduate School
of Medicine, Sendai, Japan, and the College of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan. He is a former
endurance runner.
Mayumi Kubota is a research assistant in the Department of Sports Management, Osaka
International University, Osaka, Japan.
Hiroshi Sasaki, MSc, is a professor in the Department of
Sports Management, Osaka International University, Osaka, Japan. He is a former sprinter.
Jiro Toyooka,
MSc, is a professor at the Osaka University of Health and Sports Sciences, Osaka, Japan. He is the former coach of the university's
women's Ekiden team.
Ryoichi Nagatomim, MD, PhD, is a professor in the Department of Medicine and
Science in Sports and Exercise, Tohoku University Graduate School of Medicine, Sendai, Japan.
ABSTRACT
Overtraining often compromises competitive performance in distance runners. A means for predicting overtraining in time to
take corrective action may help improve training effectiveness. Overtraining is characterised by a deregulated autonomic response
of the cardiovascular system and therefore assessment of the autonomic nervous system may provide the basis for such a means.
The authors examined whether alterations in the ratio of blood lymphocytes to neutrophils (L/N), believed to reflect the activities
of sympathetic and parasympathetic sub-systems of the autonomic nervous system, was associated with performance in four female
endurance runners over an eight-month period. Blood was sampled and analyzed monthly. The results were compared to performances
in a series of time trials plus the runners' subjective assessments of their condition. Those who performed well had lower
L/N ratios before the time trials while those who did not showed higher ratios. Although the number of subjects in the study
was small, the authors conclude that the L/N ratio shows a close relationship with performance and that an increased L/N ratio
may be associated with fatigue, exhaustion or stress in endurance runners.
Introduction
Competitive long-distance
runners train with the aim of achieving better performance in races. However, overtraining, which is characterised by a deregulated
autonomic response of the cardiovascular system, frequently compromises their competitive results. A means for predicting
overtraining or indicating the condition in time to take corrective action may help these athletes to improve the effectiveness
of their training and their performances in competition. Assessment of the autonomic nervous system may provide the basis
for such a means.
It is known that the distribution of circulating lymphocytes and neutrophils, white
blood cells that play an important part in the human immune system, is under autonomic control. In other words, the body regulates
them through a system below the level of consciousness. Moreover, a number of observations suggest that the levels of lymphocytes
and neutrophils in circulation may reflect the activities of the sympathetic and parasympathetic nervous systems, two subsystems
of the autonomic nervous system:
• there is an increase in the
proportion of circulating lymphocytes after electro-acupuncture, which stimulates the parasympathetic nervous system as detected
by decreased heart rate4;
• platelet activating factor-induced
neutrophilia, a high level of neutrophils associated with bacterial infection, inflammation
and other forms of stress,
is dependent on the stimulation of beta-adrenoceptors by catecholamines released from the adrenal glands, the "fight
or flight" response mechanism?;
• blood granulocytes and
lymphocyte subsets that increase in the daytime, show a high density of adrenergic receptors while lymphocyte subsets that
increase at night show a high proportion of cholinergic receptors.
With these points in mind, we decided
to examine whether the proportion of lymphocytes and neutrophils could be associated with the athletic performance of long-distance
runners over an eight-month period to see if this parameter could be used as an indicator of overtraining.
Methods
Subjects
The subjects, runners A-D, were four female high-school Ekiden (road relay) participants aged 15
to 18 years old. All had more than three years of experience in Ekiden competition (3.8 ± 1.0 year; mean ± SD)
and were members of a high-school Ekiden team that competed in the All Japan High School Ekiden Championships in November
every year.
As shown in Table 1, in July the subjects' height was 156.6 ± 7.1cm, body weight
was 44.3 ± 5.1 kg, % body fat was 13.4 ± 0.5% and maximal oxygen uptake was 61.2 ± 5.5ml/kg/min. The
table also gives their years of training experience and personal best time for 3000m.
Performance
Assessment
The results in a series of 3,000m time trials were used as an indicator of athletic
performance. The subject's condition was considered "good" when her performance improved on her personal best or
the time was within 2% of her personal best. Each runner's condition was also assessed on the basis of her subjective comments
after time trials and races and of the basis of the time achieved for her segment of the Ekiden Championship race, taking
into consideration the course profile (percentages of uphill, downhill and flat).
Blood sampling and analysis
Blood was sampled in the morning within two hours of breakfast once or twice per month from
April to November, and analyzed for the numbers of leucocytes, lymphocytes and granulocytes. The performances in the time
trials were compared to the lymphocyte to neutrophil (UN) ratio of the blood samples obtained within the five days before
each time trial (Figure 2), and the correlation coefficient was calculated. Statistical significance was determined as P<0.05.
Case Study - Runner A
Runner A was the only one of the subjects considered
well-conditioned throughout the study. She had a good performance in a race in June, when lymphocyte count was dominant. In
the autumn, when the lymphocyte count was still dominant, she achieved a time close to her personal best in the 3000m time
trial before the Ekiden Championships and was then ranked 4th in her section in the championship. See Figure 1 A.
Case
Study - Runner B
Runner B suffered anaemia in May, and did not participate in competitions
until the summer. At the end of the summer, she was still anaemic despite iron supplementation. Lymphocyte count became dominant
one month before the Ekiden Championships but then returned to neutrophil predominance. Her performance in the championships
was not satisfactory, which was probably due to her anaemia. See Figure 1 B.
Case
Study - Runner C
In spring, Runner C's neutrophil count was predominant but her record in
an 800m time trial was satisfactory. In the autumn, a predominant lymphocyte count lasted for a considerably long period and
she broke her personal record in a time trial 10 days before the Ekiden Championships. However, the blood test just before
the championships showed a predominant neutrophil count. Runner C was not informed of this result, but her performance in
the championships was unsatisfactory. See Figure 1 C.
Case
Study - Runner D
The initial blood test for Runner D showed predominance in neutrophil count,
but it soon showed lymphocyte predominance lasting nearly three months. Soon after the neutrophils count again became predominant
at the end of July, she had an unsatisfactory result in a 3000m competitive time trial. Lymphocyte count became predominant
again in October when her record at the pre-championship trial was close to her personal best. Five days before the Ekiden
Championships, she not only became neutrophil predominant but also developed a fever. Runner D participated in the championships
but her performance was unsatisfactory.
Relationship
between 3,000m performance and UN ratio
Two of the subjects, Runner A and Runner D, showed
good condition in the 3000m time trial performances over the eight-month period of the study, while the other two did not.
The two who showed improvements had a higher L/N ratio before the time trials and the Ekiden Championships in November while
those who failed to improve showed a lower L/N ratio before the time trials and the championships. Figure 2 shows the relationship
between percentage gain or loss in the 3000m time trials and the L/N ratio of 11 data points from the four runners over the
eight-month study period. A statistically significant correlation with a coefficient of 0.662 was found (P < 0.05).
Discussion
Performance in the 3000m time trials or the subjective condition of the subjects tended to be better when lymphocyte count
was predominant, and poorer when neutrophil count was predominant. Although these are preliminary observations in a small
number of runners, we can assume that the UN ratio is a good reflection of the physical and possibly psychological condition
of individual runners. A statistically significant correlation between the 3000m time trial result index and UN ratio with
a correlation coefficient of 0.66 implies not only an intra-individual relation but also a general trend among runners.
It is possible that this correlation may represent a dichotomous distribution of blood Iymphocytes
and neutrophils, as suggested in a previous study that demonstrated a predominance of killer-type lymphocytes and neutrophils
during the day and of helper type lymphocytes at night. Further studies are required to confirm this relationship.
The night-time profile of leucocytes, which is thought to be parasympathetic-driven, may be a representation of better recovery
from fatigue or exhaustion in the morning. Therefore, the UN ratio may a useful factor to determine the correct daily training
volume (running distance per day) to prevent overtraining syndrome in an endurance runner.
DHABHAR
et al. reported a decrease in the number of circulating lymphocytes in rats induced by acute stress, which was reversed by
adrenalectomy (surgical removal of the adrenal glands). Administration of a glucocorticoid blocker also inhibits the decrease
in circulating lymphocyte number caused by acute stress. We have also suggested that endogenous glucocorticoid (gluccorticoid
naturally produced by the body) may account for lymphopenia (abnormally low level of Iymphocites) through up-regulation of
chemokine receptors on T Iymphocytes. Taken together, the present observations of the poorly performing runners with
decreased proportions of circulating lymphocytes suggests that increased levels of physical or psychological stress induces
adrenocortical hormones as well as sympathetic activity.
Conclusion and future perspective
1. Performance in 3000m time trials
and the subjective condition of female highschool runners tends to be better when lymphocyte count is predominant, and
poorer when blood neutrophil count is predominant.
2. These results suggested that the ratio
of peripheral neutrophil to lymphocyte may reflect the physical and possibly the psychological condition of individual runners.
The L/N ratio may serve as one of the considerations for determining daily training volume (running distance per day) to prevent
overtraining syndrome in an endurance runner.
3. Although the number of subjects in the study
population was small, the L/N ratio showed a close relationship with the competitive performance. Increased UN ratio may be
associated with fatigue, exhaustion or stress in endurance runners.
4. Autonomic and HPA axis
(hypothalamopituitary-adrenal axis) dependent regulation of L/N balance need to be further investigated.
FROM: IAAF NSA 4-2009
