Table 1.

Human studies on effects of physical activity on peptides and cognition: insulin growth factor 1 (IGF-1).

Reference and Study Design	Subjects	Target Area	Type of PA	(Neuro) Peptide	Main Results
RCT [29]	33 M and F Sedentary with mild cognitive impairment. 55–85 years old (mean age: 70 years)	Executive function and short-term memory	Acute aerobic exercise	IGF-1	For women, aerobic exercise improved cognitive performance. For men, aerobic exercise increased plasma IGF-1 levels and improved performance on trails B test.
RCT [30]	62 M Sedentary 65–75 years old	Executive function, short-term memory, attention and long-term episodic memory	Acute, moderate- and high-intensity resistance exercise	IGF-1	Moderate and high-intensity resistance training have equally beneficial effects on cognition. IGF-1 levels were higher in subjects compared to controls.
RCT [31]	37 F Sedentary 65+ years old	Selective attention, cognitive flexibility, and processing speed	Acute aerobic exercise	IGF-1	Taekwondo training may improve physical fitness and cognitive functioning in elderly females. IGF-1, VEGF and BDNF may mediate the latter effect.
Longitudinal study [32]	303 M and F Followed from age 13 to 42 years old	Executive functioning and visual-spatial memory	Physical activity and fitness were assessed annually between ages 13 to 16. At mean age 36, physical activity and fitness were assessed.	IGF-1	For males, there is a significant association between physical activity in adolescence and cognitive capabilities in adulthood. Such association was not found for females. IGF-1 was not found to have an intermediate role for either sex.
Controlled trial [33]	23 M and F Untrained 18–30 years old	Short- and mid-term memory	Regular resistance exercise	IGF-1	10 Week strength training period did not influence serum BDNF, IGF-1 or IGFBP-3 levels. There was no difference in short-term memory between experimental and control group. Mid-term memory was not improved after 10-week training program.
Between-group design [34]	91 M and F Healthy, both sedentary and physically active 14–18 years old	Selective attention, cognitive flexibility, processing speed, spatial memory, spatial memory and primary visual cortex function	Regular aerobic exercise	IGF-1	Regular aerobic exercise improves cognitive function in teens and these beneficial effects are associated with serum levels of BDNF and VEGF. No such association was found for IGF-1.
Cross-sectional study [35]	22 M and F 65–85 years old (median age: 77 years)	Temporo-spatial orientation, memory, attention, calculation capacity, language, and pragmatic praxia	Questionnaire about physical activity and performance	IGF-1	No association between physical activity and GH or IGF-1 levels were demonstrated. There is a direct relationship between cognitive function and IGF-1 plasma levels in aged subjects with cognitive impairment.
RCT [36]	60 M Exercise status was not mentioned 20–29 years old	Executive function, inhibitory control and attention	Acute resistance exercise	IGF-1	The beneficial effects of resistance exercise on cognitive function might be explained by changes in arousal state. The change could possibly be modulated by serum cortisol levels.
Cross-sectional study [37]	114 M and F Physically active 60+ years Old (mean age: 66 years)	Executive function, visuo- construction, concentration/attention, language, and memory	Regular aerobic exercise	IGF-1	Extensive aerobic training might be beneficial in maintaining cognitive function in older age. BDNF and IGF-1 was not found to be associated with duration of daily exercise and no differences in the basal levels of BDNF and IGF-1 between exercise and control group was found.

M, males; F, females; RCT, randomized controlled trial; PA, physical activity.