Introduction: Very little attention has been paid to the thickness of the diaphragm (DT) as an important aspect of architecture of the respiratory muscle and the possible effect of occupation-related unregulated physical activity on it.

Aim of the research: This study aimed at assessing the effect of occupation-based physical activity on the thickness of the thoracic diaphragm.

Material and methods: Eighty (80) males between the ages of 18 and 30 years were recruited for the study and divided into two (2) groups: a control group of forty (40) relatively inactive subjects and a quasi-experimental group of forty (40) peasant labourers. The peasant labourers were recruited from a settlement of local craftsmen and motor-mechanic artisans. B-mode ultrasound was used to measure the thickness of the diaphragm (DT).

Results: The mean DT of the quasi-experimental group was higher than that of the control group (p > 0.05 – not significant), even though the control group presented significantly greater weight and body mass index (p < 0.05) than the age-matched Labourers.

Conclusions: These findings indicate that occupation-based unregulated physical activity increases DT and may initiate the setting in of diaphragmatic hypertrophy induced by occupation-associated strength and anaerobic training. The findings will also serve as a guidepost in the biomechanical aspects of the muscle during respiration in our sub-Saharan African population.