DON'T be alarmed if one day your doctor puts down the prescription pad and instead recommends a good dose of bench presses.
It might sound shonky, but a new study by Griffith University scientists shows that resistance exercise administered at different doses results in unique increases in key white blood cells in the circulation, all of which are either central to immune defence against infection or aid in healing an injury.
Published in Immunology Letters, the study collated and analysed the results of 16 previous studies from 1989-2016, which investigated participants undertaking a single session of resistance exercise encompassing various exercises.
"We already knew that aerobic exercise such as moderate intensity walking (20 minutes a day, five days a week) could stimulate the immune system and reduce the risk of upper respiratory tract infections (URTI), but not a great deal was known about resistance exercise in particular, and specifically if the dose (or amount) of resistance exercise would make a difference," said Dr Adam Szlezak from Griffith's Menzies Health Institute Queensland.
"From analysing all 16 studies we found that both high and low dosages of resistance exercise increased the immune system's surveillance potential in the participants in a similar way to that of aerobic exercise.
"Even a low dose of thumb resistance exercise increased the number of key white blood cells in the circulation.
"Importantly, we also found that at higher dosages of exercise (such as a circuit protocol), there appeared to be a more rapid and greater number of these cells in the blood."
Dr Szlezak said now researchers knew that different resistance exercise doses can result in distinct biological responses, much like drugs can, it remained to be seen if these responses can be used to reduce risk of UTI, as well as improve recovery from illness and injury.
Practically speaking, since resistance exercise appears to improve immune-surveillance similar to that of moderate intensity aerobic exercise, regular moderate-intensity 20-45 minute workouts in the gym may provide similar protection against URTI.
"It may even eventually be possible to prescribe resistance exercise in a healthy limb to improve the transport of white blood cells to an injured limb, aiding with healing and effectively changing the way we manage injuries," Dr Szlezak said.
"As we now know that exercise can markedly affect the number of white blood cells in the circulation for a short period of time, general practitioners requesting full blood counts for patients are advised to recommend that their patients abstain from all forms of exercise in the hours prior to blood collection."