Samenvatting

Introduction: Strenuous physical stress induces a range of physiological responses,
the extent depending, among others, on the nature and severity of the exercise, a
person’s training level and overall physical resilience. This principle can also be used
in an experimental set-up by measuring time-dependent changes in biomarkers for
physiological processes. In a previous report, we described the effects of workload
delivered on a bicycle ergometer on intestinal functionality. As a follow-up, we here
describe an analysis of the kinetics of various other biomarkers.
Aim: To analyse the time-dependent changes of 34 markers for different metabolic
and immunological processes, comparing four different exercise protocols and a
rest protocol.
Methods: After determining individual maximum workloads, 15 healthy male
participants (20–35 years) started with a rest protocol and subsequently performed (in
a cross-over design with 1-week wash-out) four exercise protocols of 1-h duration at
different intensities: 70% Wmax in a hydrated and a mildly dehydrated state, 50% Wmax
and intermittent 85/55% Wmax in blocks of 2 min. Perceived exertion was monitored
using the Borg’ Rating of Perceived Exertion scale. Blood samples were collected both
before and during exercise, and at various timepoints up to 24 h afterward. Data was
analyzed using a multilevel mixed linear model with multiple test correction.
Results: Kinetic changes of various biomarkers were exercise-intensity-dependent.
Biomarkers included parameters indicative of metabolic activity (e.g., creatinine,
bicarbonate), immunological and hematological functionality (e.g., leukocytes,
hemoglobin) and intestinal physiology (citrulline, intestinal fatty acid-binding protein, and zonulin). In general, responses to high intensity exercise of 70% Wmax and intermittent
exercise i.e., 55/85% Wmax were more pronounced compared to exercise at 50% Wmax.
Conclusion: High (70 and 55/85% Wmax) and moderate (50% Wmax) intensity
exercise in a bicycle ergometer test produce different time-dependent changes in
a broad range of parameters indicative of metabolic activity, immunological and
hematological functionality and intestinal physiology. These parameters may be
considered biomarkers of homeostatic resilience. Mild dehydration intensifies these
time-related changes. Moderate intensity exercise of 50% Wmax shows sufficient
physiological and immunological responses and can be employed to test the health
condition of less fit individuals.