What Qualifies as Intense Exercise?
We’re talking about anything that gets us up close to our maximum heart rate, involving a large contribution from anaerobic energy systems (more on this later) - the stuff that we can’t sustain for long periods of time. Just a few examples are:
- Conventional strength training (but only the kind that prescribes multi-joint, compound movements - not the upper body isolation exercises/chat to your friend type!)
- Interval Training (running, cycling, rowing, boxing etc)
- Circuit Training (with weights or body weight etc)
- Strongman sessions
- Hill Sprints
Where The Energy Comes From
To understand what’s really going on when we exercise we need to have at least a basic knowledge of the three energy systems and the effect of using each one.
Energy System One - The Phosphagen System (Anaerobic)
This system provides Adenosine Triphosphate (ATP), which is the energy currency of the cell, for short-term / high-intensity activities (e.g. strength training/sprinting) and is active at beginning of exercise regardless of intensity, but also at the start of each high intensity interval. The system is able to provide large amounts of ATP very quickly but has very limited reserves - enough to fuel us for about 6 seconds of intense work.
Energy System Two - The Glycolytic System (Anaerobic)
The second system involves the breakdown of carbohydrate (glycogen stored in the muscle or glucose in the blood stream) to form ATP. This system is also powerful and is capable of being the main energy provider for about 30-40 seconds. However this process involves metabolic by-products which are known to bring about discomfort (‘the burn’), although this is not caused by lactic acid as once thought.
Both of these systems are anaerobic systems, meaning that they do not require oxygen to work.
Energy System Three - The Oxidative System (Aerobic)
The oxidative system, more commonly referred to simply as the aerobic system (meaning that it requires oxygen to work) is the primary source of ATP at rest and during longer duration/lower intensity activities like walking, jogging, cycling etc. The system provides ATP via the combustion of mainly carbohydrates and fats, although protein will also be broken down during prolonged aerobic training.
It is important to appreciate that all of these energy systems are working at all times, it is just the degree to which each one is used that changes depending on the intensity of the exercise bout. For example if you go out jogging the vast majority of ATP is being supplied by the aerobic system, with minor contribution from the two anaerobic processes. However when you ramp up the intensity by e.g. doing sets of intense front squats or sprints - it’s all hands on deck! While the anaerobic system is taking the lead role in providing ATP, the aerobic system is also working hard to support the anaerobic processes during the rest intervals. Try talking to one of our members just after the fourth set of front squats. You will soon appreciate that there is a huge aerobic component to strength training!
So it can be said that while both steady state cardio and high intensity training both lean heavily on the aerobic system, high intensity training is the only method that leans heavily on anaerobic processes as well. This distinction is important.
The After Burn Effect
So it’s clear that during exercise the body is supplied ATP by both aerobic and anaerobic processes. After the exercise bout has concluded the body regroups and goes into restoration mode. During this time it is necessary for the body to metabolize even more fuel in order to reload energy stores and depleted oxygen in the muscles and blood. Specifically extra fuel continues to be utilized because of:
- Elevated core body temperature
- Increased activity of the cardiovascular system
- Elevated secretion of hormones that increase metabolic activity
- Energy system reload
- Recovery of muscle damage
This process is known as Exercise Post Oxygen Consumption (EPOC) and is a key ally in the battle against the bulge. With steady state cardio the period of EPOC is known to be fairly insignificant - often only a few minutes. The story is quite different with high intensity anaerobic exercise though, especially when it comes to intense strength training. A study by Scheunke et al, published a study in the Eurpopean Journal of Applied Physiology found that an intense resistance training session elevated EPOC for 38 hours post-training. That’s huge! That means if you train hard on Monday morning, your metabolism continues to burn calories at an elevated rate until midnight on Tuesday. Now imagine training 3-4 times per week like we do at Primal Strength...that would mean your metabolism is elevated above it’s normal rate most of the time. The key here is this only really happens when you’ve been exercising intensely/anaerobically.
Increasing your Resting Metabolic Rate (RMR)
When it comes to fat-loss, the extra calories burned by the EPOC effect are a bonus but the metabolic boost is temporary in nature. Eventually the rate at which calories are burned returns to what is known as our Resting Metabolic Rate (RMR). However there is also a way to increase our RMR. It has been shown that increasing our muscle mass can permanently raise our RMR because muscle is metabolically active - and so more muscle requires more calories to operate. It stands to reason that if we are able to increase the RMR there would be a positive effect on our body composition. Similarly the caloric cost of any conditioning work that we do, be it high-intensity or steady-state could be elevated if we have increased our muscle mass. On the other hand Broeder et al (1992) found that even 12 hours a week of endurance training didn't raise RMR at all. This is an important point to consider because while calories burned during exercise are great, and while EPOC is a welcome boost the reality is that around 70% of our daily calories are burned by our RMR.
But for muscle mass to be added the right hormonal environment must be created. As mentioned earlier, during the post-exercise restoration period the body up-regulates the secretion of certain hormones. Two key hormones, which have an intimate relationship with each other are Testosterone and Cortisol. Testosterone is anabolic in nature and so has a positive effect on protein synthesis and muscular growth. Cortisol on the other hand is a catabolic hormone secreted in response to physical and physiological stress. Cortisol attempts to help maintain blood glucose levels by breaking down skeletal muscle and adipose tissue to increase amino acid and lipid availability. It has also been shown that elevated levels of circulating cortisol has a negative effect on testosterone production, thus creating a net catabolic environment within the body. This is obviously a situation we must avoid if we are in the pursuit of lean muscle mass. Brownlee et al (2005) confirmed that aerobic protocols will bring about elevated levels of cortisol secretion and an associated reduction in circulating testosterone. Long-term this will lead to a reduction in lean muscle mass and assumedly a reduction in RMR. On the other hand several studies, including a long-term study conducted by Fry et al (2000) have shown that during a competitive weightlifting season the ratio of cortisol:testosterone remains on the anabolic, muscle promoting side of the fence.
Strength Training - The Elixir of Life
There are of course more benefits to increasing muscle mass than just improved body composition. It’s a scary thought but as we age there are processes that begin to occur in the body that if left unchecked will deteriorate our quality of life in our golden years. The most problematic are:
- Sarcopenia - the age related loss of muscle mass that was once thought to occur in our fifties but actually begins in our late twenties! It has been shown that on average we lose about 1% of our strength per annum from the age of 28. This has been shown to cause more atrophy in our type II (fast twitch) fibers, explaining why we can maintain strength well through life, but not power. If you’re sick of your Dad telling you how fast he used to be, give him a break - he might just be telling the truth!
- Nervous System changes i.e. The rate that the nervous system can conduct impulses to the muscles decreases. This also contributes to a loss of strength and power, which is important as these qualities appear to be key factors in determining functionality in later life.
- Osteoporosis - a reduction in Bone Mineral Density (BMD), which is associated with increased risk of fracture.
The good news is that all of these processes can be slowed down and even reversed with strength training. Numerous studies show that BMD is increased with strength training and studies by Häkkinen et al (2000), Kraemer et al (1999) and Schulte et al (2001) have demonstrated that both neural function and hypertrophy are trainable at any age. In fact Schulte et al reported that trainees in their sixties were capable of almost the same rate of hypertrophy as their ‘young buck’ counterparts. They also demonstrated that significant improvements in hypertrophy, strength and power were achievable in elderly populations with resistance training, and some of their subjects were in their nineties so it really is never too late! While strength training has been shown to have profound effects on functionality in elderly populations, aerobic protocols have been shown to be of little benefit (Fiatarone et al, 1994). Tufts University now teaches that the most accurate biomarker of longevity in humans is no longer blood pressure or total cholesterol but rather muscle mass, i.e. the greater the muscle mass in older populations, the greater the longevity potential.
Why then would we base our health on a foundation of aerobic training when it has been shown to reduce our muscle mass? Sarcopenia + an exercise plan that may reduce muscle mass is a strange combination for long term health in our opinion.
Still Need Convincing?
Make a point of reading some of these:
Strength training can help to preserve muscle mass and lower body fat better than aerobics.
Geliebter A, et al. Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects. Am J Clin Nutr 1997;66:557-563.
Performing only aerobic work appears to do little to prevent age related muscle loss and metabolic decline.
Williams PT, Wood PD. The effects of changing exercise levels on weight and age-related weight gain. Int J Obes (Lond). 2006;30:543-551.
Intense exercise can offset the effects of age related metabolic decline
Van Pelt RE, et al. Age-related decline in RMR in physically active men: relation to exercise volume and energy intake. Am J Physiol: Endo Metab 2001;281:E633-E639.
Strength training increased EPOC and fat oxidation hours after finishing
Osterberg KL & Melby CL. Effect of acute resistance exercise on postexercise oxygen consumption and resting metabolic rate in young women. Int J Sports Nutr Exerc Metab 2000;10:71-81.
No EPOC was found for the low to moderate intensity exercisers.
Poehlman ET, et al. The impact of exercise and diet restriction on daily energy expenditure. Sports Med 1991;11:78-101.
Strength training increased EPOC and fat oxidation hours after finishing
Hunter GR, et al. Resistance training increases total energy expenditure and free living physical activity in older adults. J Appl Physiol 2000;89:977-984.
Strength training increased EPOC and fat oxidation hours after finishing
Poehlman ET, Melby C. Resistance training and energy balance. Int J Sport Nutr 1998;8:43-59.
EPOC is positively related to intensity
Sedlock DA, et al. Effect of exercise intensity and duration on postexercise energy expenditure. Med Sci Sports Exer 1989;21:662-666.
Aerobic training doesn’t appear to be a very effective weight loss modality for women
Gleim GW. Exercise is not an effective weight loss modality in women. J Am Coll Nutr 1993;12:363-367.
45 minutes of cardio, 5 x per week for 12 weeks didn’t yield greater results than nutrition interventions alone.
Utter AC, et al. Influence of diet and/or exercise on body composition and cardio respiratory fitness in obese women. Int J Sport Nutr 1998;8:213-222.
4 hours per week of aerobic training had no effect on weight loss
Van Dale D, et al. Does exercise give an additional effect in weight reduction regimens? Int J Obes 1987;11:367-375.
Interval training resulted in better fat-loss than endurance training - even though the interval training group expended less energy during each session
Tremblay A, et al. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism 1994;43:814-818.
Wrapping it up
In our opinion, when it comes to straight out fat-loss, strength training happily shares the limelight with other high intensity modalities like interval training. For example we are currently experimenting with the highly promising Bangsbo 10-20-30 Protocol to see how well it fits in with our Primal Strength sessions. We'll update you with information on that soon.
However when it comes to long-term health and combating the effects of aging, strength training alone is the winner. Since strength training is effective at improving our body composition, health and quality of life as we age, we believe that it should form the cornerstone of every training plan.
But that doesn't mean that we think you should just do strength training. Conditioning work, be it high intensity or steady state must have its place in your training week.
On paper high intensity conditioning work appears to trump aerobic training for fat-loss as well as raising VO2 max. The trouble is that high intensity conditioning is very challenging, especially at first and it can become quite hard to motivate yourself for - especially if training on your own. On the other hand aerobic training is less daunting as the relative intensity is much lower. You can just plug in your ipod and off you go. It’s perhaps not optimal but for many people it’s something they are much more likely to stick with and so is definitely the way to go.
For us, strength training is the only non-negotiable part, but after that it’s up to you. If you can keep yourself motivated to train at a high intensity all of the time then go for it. If not then make time for some aerobic work on top of your strength training. A combination of high intensity conditioning work and aerobic work works fine too of course.
Put simply, a training plan based around aerobic training is for endurance athletes, strength based programs are for the rest of us.
In the next few weeks we will be releasing a conditioning booklet to be used in conjunction with our Primal Strength sessions and our nutrition resource A Guide to Primal Eating, which will be available to all of our members. More details on this to follow.
Eur J Appl Physiol. 2000 Sep;83(1):51-62.
Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly people.
Blankfort-Doyle W, Waxman H, Coughey K. An exercise program for nursing home residents. In: Ostrow AC, ed. Aging and motor behavior. Indianapolis: Benchmark Press, 1989:201-6.
Molloy DW, Richardson LD, Crilly RG. The effects of a three-month exercise programme on neuropsychological function in elderly institutionalized women: a randomized controlled trial. Age Ageing 1988;17:303-310
Brownlee1, Alex W. Moore1 and Anthony C. Hackney1, 2 ©Journal of Sports Science and Medicine (2005) 4, 76-83 http://www.jssm.org Research article
RELATIONSHIP BETWEEN CIRCULATING CORTISOL AND TESTOSTERONE: INFLUENCE OF PHYSICAL EXERCISE
KRAEMER,2 MICHAEL H. STONE,3 PERRY KOZIRIS,4 JOHN T. THRUSH,5 AND STEVEN J. FLECK6 Journal of Strength and Conditioning Research, 2000, 14(3), 338–343
2000 National Strength & Conditioning Association Relationships Between Serum Testosterone, Cortisol, and Weightlifting Performance ANDREW C. FRY,1 WILLIAM J.
Schuenke MD, et al. Effect of an acute period of resistance exercise on excess post-exercise oxygen consumption: implications for body mass management. Eur J Appl Physiol 2002;86:411-417.
Broeder CE, et al. The effects of aerobic fitness on resting metabolic rate. Am J Clin Nutr 1992;55:795-801.