Came across this fascinating study into load carrying in Defence and its impact on performance.
Warning: it's 70 pages!
Here's a snippet from the Abstract:
An individual's load carriage capacity is influenced by a multitude of factors that can broadly be
categorised into three groups; 1) personnel characteristics (e.g. fitness, body mass, gender, age, injury profile, load carriage experience),
2) task characteristics (e.g. total external load, distribution of load, load carriage equipment design, movement speed, march duration,
work to rest ratio) and 3) environment (e.g. terrain, heat, humidity, altitude) in which the task is performed. Some of these factors may
in some situations be controlled (e.g. marching speed) whilst others are not (e.g. ambient temperature). There is a dynamic interaction
between these factors which ultimately impact on an individual's load carriage capacity.
https://www.dst.defence.gov.au/sites/default/files/publications/documents/DSTO-TR-2765.pdf