The goal of this project is to compare different ways to schedule a workday to see if older workers should follow a specific work protocol to reduce strain on the heart and muscles across two consecutive days of work.

Participants will come to the lab a total of six times. During four of the visits participants will complete a box carrying task, simulating unloading a delivery truck. This will take place in a hot and humid room to simulate being outdoors during the summer.

Inclusion Criteria:

• Healthy individuals
• 18-29 years old and 40-65 years old
• Completes at least 120 minutes of moderate to vigorous physical activity each week for at least the past 4 weeks
• Resistance trained or have recently held a job involving box carrying or a similar task

Exclusion Criteria:

• History of cardiovascular, metabolic, respiratory, neural, or renal disease
• Hypertensive (systolic blood pressure > 139 mmHg or diastolic blood pressure > 89 mmHg) or tachycardic (resting heart rate > 100 bpm) during the screening visit
• Current nicotine use or previous use within the past 6 months
• Current of previous musculoskeletal injury limiting physical activity
• A positive pregnancy test at any point during the study
• Currently breastfeeding
• Study physician discretion based on any other medical condition or medication

A spreadsheet of the cleaned, de-identified individual data for all variables will be shared on at clinicaltrials.gov without restriction to ensure public availability. Individual data will be identified using unique participant identifier numbers. In addition to the datasets, a study protocol, data dictionary defining and describing all variables, and data collection instruments will be shared and associated with the relevant datasets.

Data from this project will be made available as soon as able and no later than the time of the final publication. Original data will be preserved indefinitely after the end of the funding period.

Pooled and de-identified data will be made available to interested researchers upon email request.