Rickshaw Physiology
A study conducted by Chandan K Prahdan et al. in 2008 analyzed the energy expenditure of rickshaw drivers in India. We can imagine that the physical requirements of jews in the ghettos would have been fairly similar. Although conditions are not necessarily the same today as they were then, the energy requirements of the job haven't changed much in non-automotive rickshaw driving.
The 2008 study showed that the energy expenditure of rickshaw drivers averages to about 24 kJ/min, which comes to about 344 kilocalories/hour. Pulling a rickshaw was heavy work and bears heavy demand on a driver's cardiovascular systems and muscle contractility (force of muscle contraction).
For Jewish rickshaw drivers who would have been living on 181 kcal/day, and losing about 344 kcal/hour, the energy demands of even just one hour of work, exceeds the number of kcalories obtained from food.
With this level of malnutrition in concentration camps, prisoners would have experienced increased cardiovascular, muscular, and metabolic problems such as hypotension and perpetual fatigue. For example, prisoners often experienced orthostatic intolerance categorized by increased fainting and the inability to stay standing for long due to the increased cost of getting blood back to the heart, and oxygen to the brain. It is amazing that these men were able to pull these rickshaws at all and speaks to the sheer resilience of these workers who managed to persevere.
Pradhan, C.K., Thakur, S., Mukherjee, A.K., & Roychowdhury A. (2008). Energy expenditure of cycle rickshaw pullers in different places in India. Ergonomics, 51(9), 1407-1417. https://doi.org/10.1080/00140130802120226