I know of no such regulations in the Greco-Roman world, but it may be just my ignorance and I should be happy to be enlightened. Regulations about loads must have existed, for the load (
govmo") of an ass or a camel were standard units for tax purpose: e.g. in the Hellenistic tariff inscription in the collection of the Institute of Archaeology of the Hebrew University, published by I.L. Merker in
IEJ 25 (1975) 238-244, and in the 2nd-c. CE Palmyra tariff edict (OGIS 629; J.F. Matthews,
JRS 74 [1984], 157-180). Liquid commodities transported in jars were also taxed by container and no doubt the containers had to fit a known standard of capacity. A. Raban, in his paper ‘Jars and standard volume’, in
Measuring and Weighing in Ancient Time (Museum Hecht, Haifa, 2001), 13-21 (Hebrew), 11*-14* (English), has shown, convincingly in my opinion, not only that jars were manufactured according to fixed sizes and volumes, but also that the size and volume were chosen to accommodate the porters. An amphora to be carried on a porter's shoulder would be as high as the average length of a man's arm, and its weight (container + liquid commodity) would not be such as to endanger the man — most likely not for his health sake but to avoid his dropping the jar and so causing the loss of the expensive commodity. Double amphoras were manufactured in size and volume (and shape) apt to be carried by two men: so were the lmlk jars made in Judah in the 8th-7th c. BCE. In other words, there must have been regulations pertaining to a man's load, as well as a beast's load, but their purpose would have been practical (mostly for tax, toll and custom purposes) not social or humanitarian.
Regards,
Leah Di Segni
PS: BTW, the full load of a mule in the 5th-6th c. CE was 12 modii of grain (105 litres, about 82-84 kg at the specific weight of wheat), and Cyril of Scythopolis, Vita Sabae 44, tells of an Herculean monk who could easily lift and carry one such load, and on one occasion, having killed the mule with a head punch in a fit of anger, carried home to the monastery not only the full load but also the pack saddle.