Maria Westerståhl is a senior lecturer and physiologist at the Karolinska Institutet in Sweden, where she leads long-term research into how physical fitness and activity change across the human lifespan. With an academic background in nutrition and physiology, she teaches a range of health and exercise-related courses and supervises research on topics from cardiovascular risk in children to ageing and muscle function. Westerståhl is best known for directing the Swedish longitudinal SPAF-1958 cohort study, which has tracked physical capacity from adolescence into later adulthood, providing rare insights into how strength and endurance evolve with age and lifestyle.