The 30-second article
• Often called the ‘ powerhouse ’ of the cell , for its ability to oxidise fuel sources to create energy , mitochondria are critical for health and the evolution of the human species
• Physical activity causes an increase in the number of mitochondria
• A complex interaction between several ‘ energy sensors ’ in the muscle and ‘ co-activators ’ cause proteins to become transcribed and form into mitochondria
• Nutrition and nutrient-timing , specifically training after fasting or following a low-carbohydrate meal , can favourably affect mitochondrial adaptation .
Aerobic exercise that emphasises volume ( continuous aerobic endurance training ) or intensity ( such as high intensity interval training – HIIT ) is generally regarded as the most potent controller of the growth and function of mitochondria . Research indicates that volume plays the greatest role in the growth and size of mitochondria , and intensity appears to regulate their function . It is difficult , therefore , to definitively say whether HIIT or continuous exercise are ‘ better ’ for mitochondria as they both facilitate different effects , but a very recent study has shown that when matched for total volume , HIIT appears to have the edge . Resistance training , at this time , has a lesserknown role in the regulation of mitochondria .
Nutrition and mitochondria
Research has begun to explore the potential role of nutrition , supplements and the timing of food intake on mitophagy and the regulation of mitochondria . Time-restricted feeding , periodic fasting and fasting-mimicking diets are all promising interventions . Both timerestricted feeding and fasting-mimicking diets increase the activity of AMPK and thus promote the transcription of PGC-1α and subsequent mitochondrial biogenesis . Time-restricted feeding works on a simple premise that humans have evolved an exquisite relationship between the timing of food availability and its consumption , with periods of fasting , which correspond with sleeping time . The invention of ‘ artificial ’ light has enabled both activity and food consumption to occur when , for all of previous human evolution , we would have been asleep . Advancements in our understanding of circadian physiology have demonstrated several metabolic markers of health , including increased activity of AMPK and mitochondrial growth , when there is a daily fasting period of 12 to 14 hours .
Food components and mitochondria
Several food compounds have been shown to augment the effect of exercise on mitochondrial biogenesis in animal studies . The most promising to date are green tea extracts , sodium bicarbonate , caffeine , cocoa , resveratrol , quercetin , and certain amino acids . The vast majority of human data , however , at this early stage of investigation , has failed to find the same benefits seen in rodents . Research is currently underway to discover why this is the case .
Supplements and mitochondria
Debilitating genetic diseases that cause mitochondrial dysfunction and concurrent muscle wasting can afflict both children and adults . Due to the inability to contract skeletal muscle in these patients , there has been research interest in ‘ supplement cocktails ’ that have the potential to ‘ mimic exercise ’ and create mitochondrial biogenesis . Animal experimental models have demonstrated the potential role of certain supplements in the support of healthy mitochondria ( Creatine , l-Carnitine , α-lipoic acid , Coenzyme Q 10
, reduced nicotinamide adenine dinucleotide ( NADH )). Supplements containing nicotinamide riboside appear to have the greatest likelihood of positively affecting mitochondria . Only short-term data currently exists for the efficacy of these nutrients and long-term robust human experimentation is still needed .
Nutrient timing and mitochondrial biogenesis
Recent research has shown that performing exercise or recovering from exercise without the provision of carbohydrate has a favourable effect on mitochondrial adaptation . This can be done by performing sessions without a carbohydrate-rich meal before , or performing glycogen depleting exercise ( e . g . HIIT ) and then recovering with little emphasis on carb-rich foods and training again , depleted , or sleeping ‘ low ’ and training first thing before breakfast while withholding carbohydrate . AMPK activity and mitochondrial adaptation is significantly increased when exercise is performed in a glycogen-depleted state , when compared with muscle contracted in a state of high muscle glycogen .
Tony ’ s favourite mitochondrial boosting workouts
Interval training broadly falls under two distinct methods : 1 ) power or sprint interval training ( SIT ); or 2 ) VO 2 max intervals or high intensity interval training ( HIIT ). HIIT can be further divided into steady state intervals or short work-to-rest ratio intervals performed in series .
SIT workouts
• 4-6 x 30 seconds ‘ all out ’ with 4.5 minutes rest
• 4-6 x 20 seconds ‘ all out ’ with 2 minutes rest
• 4-6 x 60 seconds ‘ best hardest pace ’ with 4 minutes rest
HIIT workouts
• 6 x 4 minutes with 1 minute rest
• 6 x 3 minutes with 2 minutes rest
• ( 20s with 40s rest x 9 , rest 60 seconds ) x 3
• ( 30s with 30s rest x 9 , rest 60 seconds ) x 3
• ( 40s with 20s rest x 8 , rest 2 minutes ) x 3
The key to mitochondrial adaptation is stress and variety . In practice , you would ensure that over the weeks you would perform several different styles of sprint interval training ( SIT ) or HIIT , sometimes with low muscle glycogen and sometimes with high , which would then be followed by lower carbohydrate eating , sleeping ‘ low ’ and training before breakfast to ramp up AMPK .
These methods , along with regular resistance training and , perhaps , timerestricted feeding will look after our mitochondria and they , in turn , will look after us as we age .
Tony Boutagy , PhD , AES , AEP is a Sydney-based fitness professional who has been involved in training the public , coaching athletes and educating personal trainers for over two decades . He is an Accredited Exercise Physiologist , holds a PhD in Exercise Science and runs the Boutagy Fitness Institute in Sydney , a strength gym and education centre for personal trainers . tonyboutagy . com
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