MSc by Research Student

Course Start: October 2017

Supervisor: John Hough
Supervisor 2: Jeff Aldous

Working thesis title

Exercise-induced immune alterations in response to a 12-day period of intensified training

Abstract

Continuous loading of physical stress coupled with an array of potential external stressors such as inadequate nutrition, illness and psychosocial stress can induce a state of overtraining (OT). Within the athletic population, the diagnosis of OT can be detrimental towards physical performance and subsequent recovery from exercise, with athletes spending several weeks to months pursuing a full recovery. Prolonged periods of inadequate and subdued training can therefore interfere with the preparation and ensuing performance at competition. Due to the subjective nature of the symptoms surrounding OT, the development of an objective marker to measure such a state is difficult to quantify.

In response to an acute bout of high-intensity exercise, leukocytes (granulocytes, monocytes and all lymphocyte subsets) are mobilized to circulation by the activation of several multifactorial pathways to inhibit/ acutely promote (depending on intensity)  exercise-induced inflammation and promote muscle tissue recovery. Leukocytosis immediately occurs after the onset of exercise predominantly due to neutrophil demargination and lymphocytosis activation. This biphasic response will elevate until the termination of exercise. After exercise and into the recovery phase, monocyte and neutrophilic activity steadily rises to tend to the subsequent muscle damage. Lymphocytes initially rise post exercise, however drop below pre-exercise values during the early stages of recovery and slowly rise back to baseline after several hours. Acute bouts of exercise appear to be beneficial towards an individual's immune function, with 1-2 hours of exercise per day reducing the incidence of URTI’s in healthy individuals by a third.

However, the positive correlation between exercise and its relationship with immunity specifically depends on the exercise intensity, volume, duration and a variety of environmental factors. The cumulative effect of intensified training (> 6 days of intensive physical training) appears to suppress resting immune function and increase URTI susceptibility. A decreased resting neutrophil cell count, phagocytic activity, NK cell activity and a T-lymphocyte type 1/2 balance shift (Th1 cells, specifically IFN-y and IL-2 secreting CD8 cells decrease) have been observed after a period of intensified physical training.  The prevalence of immunosuppression in individuals participating in intensified training bouts therefore highlights a sensitive change to such physical demands, which potentially could highlight the onset of OT and could be the determining factor in many of the subjective symptoms seen in OT athletes.

Research Questions

• Will there be a significant elevation in immune markers (leukocyte subsets, phagocytic activity, pro/anti-inflammatory cytokines) in response to a short-duration, high intensity, RPE-paced treadmill bout.
• Can the treadmill bout identify alterations in exercise-induced immune responses before and after a 12-day bout of intensified-training?
• Will there be a blunted resting and exercise-induced immune response after the 12 days of intensified training?
• Can a 4-day resting period normalise any immune-related maladaptation which could have been induced during the intensified training period?

Contact Information

E: josh.thorley@study.beds.ac.uk
Twitter: @joshthor88
LinkedIn: Josh Thorley