Background: Many initiatives have emerged worldwide to handle the surge of hospitalizations during the SARS-CoV-2 pandemic. In France, the University of Paris North called on its medical students, whose status makes them integral members of the healthcare staff, to volunteer in their capacity of medical students and/or as nurses/nursing aids in understaffed intensive care units and other Covid-19 services. We attempted to evaluate their commitment, whether the pandemic affected their certainty for the medical profession and career choices, and how they scored their sadness and anxiety levels. Methods: The University of Paris North took a weekly official census of the involvement of 1205 4th-6th year medical students during the first lockdown in France. Six weeks after the lockdown began (May 4th), an equestionnaire was sent to 2145 2nd-6th year medical students. The survey lasted 4 weeks and documented volunteering by medical students, the association between the pandemic and certainty for their profession, their choice of medical specialty and factors that influenced sadness and anxiety scores. Results: 82% of 4th-6th year medical students volunteered to continue their internship or be reassigned to COVID-19 units. Of 802 2nd-6th year students who completed the e-questionnaire, 742 (93%) volunteered in Covid-19 units, of which half acted as nurses. This engagement reinforced the commitment of 92% of volunteers to become physicians. However, at the peak of the outbreak, 17% had doubts about their ability to be physicians, while 12% reconsidered their choice of future specialty. Finally, 38% of students reported a score of 7/10 or more on the sadness scale, and 43% a score of 7/10 or more for anxiety. Neither study year nor service influenced sadness or anxiety scores. However, gender influenced both, with women scoring significantly higher than men (p < 0.0001). Conclusion: Medical students of the University of Paris North who made an early and unconditional commitment to help hospital staff handle the pandemic constituted a powerful healthcare reserve force during the crisis. Although the vast majority remained convinced that they want to become physicians, this experience came at a significant psychological cost, especially for women. Alleviating this cost would improve future crisis responses.