Summary While at first glance seasonal work may appear relatively marginal in the labour market, it is central in a number of regions and sectors of activity. Commonly associated with natural resource exploitation (agriculture, forestry, fishing), seasonal work is also present in several other activity sectors (manufacturing, food processing, public services, etc.). This type of work differs from permanent employment because of its temporary nature, but also because of the uncertainty associated with seasonality. It is well known that seasonal workers have long working hours and alternate between “in-season” and “off-season” periods. However, little is known about the effects of these particular work patterns on the health of workers, and of effective means to prevent musculoskeletal disorders (MSDs) in such a context. Furthermore, the literature about seasonal work is very sparse, making it difficult to identify the challenges involved in MSD prevention and what is needed in the workplace. The purpose of this study is to provide relevant information to guide MSD prevention efforts in the context of seasonal work. To do so, two objectives were set: 1. To review what is known about seasonal work and its characteristics, in order to help pinpoint priority issues for MSD prevention; 2. To develop a longitudinal monitoring analysis method for certain musculoskeletal health status indicators of seasonal workers, using an existing database. To respond to the first objective, a review of the literature (a scoping review) focused on seasonal work and MSDs was conducted. Qualitative (descriptive and categorical) analyses were carried out to describe seasonal work and its characteristics, and to identify the challenges that seasonal work poses for MSD prevention. For the second objective, the overall development process was based on complementary (qualitative and quantitative) and sequential approaches to body schema analyses completed by 16 female seasonal workers at the beginning and end of each work shift over two working seasons (135,000 pain scores). Initially, an in-depth and detailed qualitative analysis of changes in pain by body region was carried out using Kiviat diagrams and informed by the verbatim interview transcripts. Next, collective statistical analyses were carried out by calculating two sets of average quantitative indicators (mean pain scores and scores obtained using a tool to measure the impact of pain on daily life (IDVQ/NULI). The indicators and the profiles obtained during the first phase of the analyses were statistically compared with these two sets of average quantitative indicators to ascertain their consistency with each other and their respective contribution to the understanding of the evolution of MSDs. The results of the first objective highlight a reality that is not well documented on its own, let alone from the perspective of MSD prevention. The context surrounding this type of work is complex and is shaped by a workforce whose vulnerability varies, depending on the profiles of the seasonal workers. Returning seasonal workers appear to be especially at risk and to suffer more from MSDs. For many seasonal sectors, activities are characterized by difficult working conditions in which considerable organizational, temporal and physical constraints are interconnected. They are usually deemed to be acceptable, because they are seen as only lasting for the duration of a season. Seasonal work is even reported as being incompatible with the management and monitoring of health problems. An understanding of this work context and principles of action in terms of MSD prevention that are relevant and effective remains fragmented, even completely absent. The results of the second objective led to the development of a longitudinal monitoring analysis method for MSDs based on a series of indicators and profiles (such as specific and/or diffuse pain, chronicity, timeline). More precisely, the indicators and the overall approach of this methodological development made it possible to describe the evolution of MSDs and to analyze, in their various forms, the variability of their fluctuating nature over time. The results of this study highlight the need for measures to prevent MSDs in seasonal settings that are based on a systemic approach to MSD determinants and that encourage the mobilization of key stakeholders. Further studies into the development and implementation of such measures would provide a better understanding of the influence of this context and would inform the actions of health professionals working in seasonal settings. Such measures and studies would benefit from being carried out in conjunction with an appropriate evaluative approach and relevant evaluation methods to make it possible to better understand the influence of this type of work context and to identify MSD prevention actions that are adapted to it. From this perspective, the longitudinal monitoring method for MSDs developed in this study could be applied to future studies as one of the evaluation methods. This analysis method is a sensitive and fine-tuned measure to assess the progression of symptoms longitudinally and has the potential to be used in combination with other methods to reveal explanatory variables related to the evolution of MSDs. Moreover, the results of the study could also guide possible choices for a follow-up study of MSDs in workplaces and for the development of approaches for ergonomic interventions. This method has made it possible to assess the chronic nature of pain and, from that perspective, is focused on the musculoskeletal symptoms of workers, not only at the end of the workday but also at the beginning of the work shift. This methodological development has led to very valuable findings for the understanding of MSDs. In particular, the findings revealed a very worrisome situation for female workers with a profile of diffuse pain. These workers have the highest mean pain scores and the impact of that pain on their daily lives is significant. This methodological development underscores the importance of the longitudinal dimension of studies and workplace intervention approaches in helping to target priority situations for MSD prevention, as well as to assess the effects and impacts of the change initiatives implemented. Finally, a longitudinally-based study of the timeline of MSDs using the indicators developed in this study will be a worthwhile avenue of investigation to better understand the effects of interrupted exposures on MSDs, particularly in terms of the alternation between work seasons and off-seasons.