Divergent effects of resistance and endurance exercise on plasma bile acids, FGF19, and FGF21 in humans Digest
Endurance and resistance training are associated with distinct hormonal signatures Exercise is widely accepted to be beneficial to our health. Research finds it to have a positive dose-dependent impact on factors varying from cognitive function and bone strength to all-cause mortality and metabolic health. But does the specific mode of exercise make a difference? A 2018 study suggests that resistance and endurance exercise engage largely distinct hormonal responses in the body. It also highlights endurance training as a particularly useful tool for engaging biochemical signals that can help combat substance addiction.
To compare resistance and endurance training, researchers recruited ten healthy young men (average age 24 years) to participate in a cross-over study. This meant that each participant engaged in both forms of exercise, with half randomly selected to first perform a one-hour endurance training session before “crossing over” to one resistance training session after a 6-to-12-day rest period. The other half of the participants followed the reverse order.
Training sessions were individually tailored to ensure equivalent levels of physiological stress across participants. For instance, resistance training sessions required participants to complete five sets of 10 reps for each exercise, at resistance levels corresponding to 90 percent of their 10 rep maximum capacity. The endurance training sessions were designed to make participants work at 70% of their VO2max(i.e. maximum oxygen uptake capacity). Importantly, participants exercised 10 hours after receiving controlled meals to prevent nutritional factors from interfering with hormone levels in their blood, which was drawn immediately before and at several timepoints after exercise.
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The experiment revealed some surprising insights into the hormonal pathways engaged by the two forms of exercise. Shortly after resistance training, participants had lower plasma levels of fibroblast growth factor 19 (FGF19) – a protein secreted by the small intestine and implicated fighting metabolic disease by stimulating the formation of metabolically active brown fatty tissue and increasing sensitivity to the satiety hormone leptin. The drop in FGF19 shortly after resistance exercise is somewhat counterintuitive given robust links between strength training and metabolic health. It raises questions about a potential long-term rebound increase following recovery, which our team looks forward to seeing explored in future studies.
Endurance exercise engaged a distinct biochemical pathway. It caused a near-triple increase in the pancreatic hormone glucagon, which stimulates the release of glucose and fatty acids into the blood. This glucagon spike was followed by an increase in plasma fibroblast growth factor 21 (FGF21) – a metabolic regulator implicated in processes ranging from fatty acid oxidation and ketone body production to the regulation of appetite for addictive substances like alcohol. The findings suggest that endurance and resistance training are associated with distinct hormonal and metabolic benefits, and that endurance exercise in particular may be a helpful strategy in combating addiction.