Neuro Athletes,

If you're reading this, I hope you're ready to get real for the next few minutes. Today, I'm going to dive into one benefit that comes from resistance training that can have a profound effect on the operating system inside your head- your brain.

Before we get into it, I want to thank everyone for listening to The Neuro Experience, my podcast that has hit top 50 globally on the iTunes charts! THANK YOU for leaving your messages and your reviews! Next week’s episode is all about hormonal health so don’t be afraid to subscribe! Also, if you are feeling super generous, feel free to leave a review. 

Primer

During the aging process, physical capabilities (e.g., muscular strength) and cognitive functions (e.g., memory) gradually decrease. Regarding cognitive functions, substantial functional (e.g., compensatory brain activity) and structural changes (e.g., shrinking of the hippocampus) in the brain cause this decline.

From a glance:

• Dementia affects approximately 47 million individuals globally with projections of 130 million by the year 2050.

• Late-onset Alzheimer's disease is the most common form of dementia, accounting for approximately 75% of all cases and is characterized by a progressive decline in cognitive function, memory, and cerebral volume.

• The pathogenesis of Alzheimer's disease is poorly understood; however, aging, genetics, and an individual's diet and lifestyle over several decades appear to be key determinants.

Excitingly, growing evidence points towards a relationship between cognition and measures of muscular strength and muscle mass. Based on this emerging evidence, resistance training, which contributes to the preservation and augmentation of muscular strength and muscle mass, may trigger beneficial neurobiological processes and could be crucial for healthy aging that includes preservation of the brain and cognition.

Myokines are muscle-derived effectors that regulate body metabolism by autocrine, paracrine, or endocrine action and were reportedly suggested as “exercise factors” that can improve the brain function. Myokines such as cathepsin B, BDNF and IGF-1 are all released from skeletal muscles in response to resistance training.

Aerobic training (AT) can support brain health in Alzheimer’s disease (AD); however, the role of resistance training (RT) in AD is not well established. Aside from direct effects on the brain, exercise may also regulate brain function through secretion of muscle-derived myokines. Recently, Cathepsin B (CTSB) has been reported to be secreted from skeletal muscles and upregulate BDNF following exercise, which was associated with improved cognitive function.

Let’s explore CTSB its effects on brain function.

Cathepsin B

CTSB, a lysosomal enzyme that plays a neuroprotective role in Alzheimer's disease. It is secreted from muscle into circulation after exercise and is associated with memory function and adult hippocampal neurogenesis. Older adults with cognitive impairment have lower serum and brain CTSB levels. Mueller-Steiner et al. (2006) and Embury et al. (2017) have demonstrated that cathepsin B is useful for halting Alzheimer's disease (AD) progression.

The link between CTSB and Exercise

Aerobic training

Using neuroimaging techniques in humans, it has been reported that aerobic exercise improved both the function and structure (volume and intensity) of specific regions related to memory and cognition, including prefrontal cortex, entorhinal cortex, and hippocampus. In fact, the hippocampal volume in healthy elderly adults was increased by a moderate-intensity (intensity reaching 50–60% of the maximal heart rate) aerobic exercise intervention for 1 year, which is consistent with the association of aerobic fitness and hippocampal volume reported by other cross-sectional studies.

Results of a recent study, published in the journal Frontiers in Endocrinology, showed that plasma CTSB levels were increased following this 26-week structured aerobic exercise training in older adults at risk for AD. Verbal learning and memory correlated positively with change in CTSB but was not related to BDNF or klotho. The present correlation between CTSB and verbal learning and memory suggests that CTSB may be useful as a marker for cognitive changes relevant to hippocampal function after exercise in a population at risk for dementia.

The positive association between CTSB and cognition, and the substantial modulation of lipid metabolites implicated in dementia, support the beneficial effects of exercise training on brain function and brain health in asymptomatic individuals at risk for Alzheimer's disease.

The positive association of aerobic exercise with hippocampal volume was observed not only in elderly adults but also in children and adolescents. The functional and structural improvement of brain by exercise is closely linked with evidence that exercise activates signaling pathways associated with long-term potentiation, synaptic plasticity, and neurogenesis in animal studies, which was further supported by human studies revealing that physical activity increases neural activity and functional network.

Resistance training 

CTSB is a novel myokine that plays a role in exercise-induced benefits to brain function. Resistance training (RT), which generates intermittent high muscular tension rather than sustained low muscular tension characteristic of AT, has been shown to increase CatB expression in healthy muscle.

The increase in plasma CTSB level following 4 months of resistance training exercise was observed in humans and showed an increase in CTSB level which was significantly correlated with hippocampal function. The plausible mechanisms of beneficial effects of skeletal muscle-derived CTSB on cognitive function include hippocampal upregulation of BDNF and doublecortin, which regulates synaptic plasticity, cell survival, and neuronal migration.

Conclusions

Aerobic exercise mainly improves cardiovascular function and/or induces non-muscle exercise factors, which mediate the improvement in cerebral circulation, followed by hippocampal neurogenesis. The effect size of resistance exercise on skeletal muscle hypertrophy might be higher than that on cardiovascular fitness effects. Therefore, the effect size according to the types of exercise on brain function may be an important concern in order to clarify the beneficial effects of exercise on the hippocampal neurogenesis.

Given the propensity of AD to develop in the elderly, RT should be included as part of an exercise intervention prior to and during AD in order to increase strength, muscle mass.

Until next time,

Louisa x