As a coach at Clean Health Fitness Institute, it is my job to provide my clients with individualised strength and cardio training programs designed to achieve their specific goal. One of the many considerations is whether to include cardiovascular exercise alongside traditional strength training, which forms the basis of clients’ programs.
This decision is often difficult due to the many differing opinions surrounding cardio and the supposed benefits and drawbacks of utilising it. This is why I want to look at what the research tells us about cardiovascular exercise and in what scenarios it may be beneficial. Having a better understanding of how cardio impacts the body will enable you to make a much more informed decision about whether to include it in your training program.
When assessing the impact of any type of exercise on the body, we need an appreciation of the ‘SAID’ principle (Specific Adaptations to Imposed Demands). In essence, when you impose a stress on the body, the body will adapt to this stress in a specific way. Strength training carried out in the gym and cardiovascular exercise, such as jogging, lie at opposite ends of the strength-endurance continuum.
LISS Cardio For Fat Loss?
Traditionally, low intensity steady-state (LISS) cardio has been seen as the ultimate ‘fat-burning’ exercise. This is due to the fact that whilst performing a low-intensity exercise such as walking, jogging, or cycling, the preferred fuel (substrate) for the body is fat (Crampes et al, 1985).
Oxygen is required to burn body fat, hence the belief that LISS is optimal for burning body fat. However, the actual substrate being used at any one time is of little importance when compared to substrate utilization over a 24-hour period. For fat loss, the most important factor to consider is energy balance, not short-term substrate utilization during a training exercise.
People make the mistake of “focusing on stored fuel usage during training instead of focusing on optimally partitioning exogenous fuel for maximal lipolytic effect around the clock” (Aragon, 2006). Put another way, if you are not in a consistent energy deficit, you will not burn stored body fat, regardless of how much cardio you do.
HIIT A Better Option?
Studies have since shown that “the effect of regular aerobic exercise on body fat is negligible” and that perhaps High-Intensity Interval Training (HIIT) may be of more benefit (Boutcher, 2011). HIIT has been touted as a revolutionary way of burning fat in a fraction of the time. So rather than jogging on a treadmill for hours on end, why not just do several sets of sprints such as on a prowler that may take only 15 minutes to complete?
Indeed, studies have found the high-intensity nature of interval training to produce greater excess post-exercise oxygen consumption (EPOC) than LISS, indicating that it may be a more effective modality for increasing total daily energy expenditure (Greer, et al, 2015).
As mentioned above, another major benefit of HIIT is that it is time efficiency. Research has shown that long bouts of LISS can result in a compensatory reduction of non-exercise physical activity (Drenowatz, et al 2015). So, whilst performing long bouts of cardiovascular exercise will result in increased energy expenditure, the overall impact may be negligible if physical activity is reduced in everyday life.
This reduction in non-exercise physical activity may be attributed to exercise-induced fatigue, which leads a person to be inactive during times when they would usually engage in some sort of physical activity.
However, whilst HIIT has the advantage of being more time-efficient, LISS tends to be better tolerated and enjoyed (Foster et al, 2015). Enjoyment is a huge factor when trying to optimize a client’s training program because quite simply the more enjoyable someone finds the training, the more likely they are to adhere to the program in the long-term.
One of the biggest battles we face, as personal trainers, is long-term adherence to programs. So you always have to take into account someone’s enjoyment and preference for the type and modality of cardiovascular exercise you might prescribe someone. In the same vein, if someone strongly dislikes cardio, then perhaps the best course of action is to prescribe more strength training sessions per week, rather than to try and force someone to do cardio.
So HIIT training is more time-efficient and has higher energy output. But the downside is that HIIT training has a far greater interference effect than LISS on strength training. For example, De Souza et al (2014) compared the effects of strength training twice a week with and without the addition of HIIT sprint training.
The group that performed strength training only gained over 17% in size in all their major muscle fibre types. However, the group performing HIIT as well found no significant increase in muscle mass. Here are some strategies to minimize the interference effect:
- Perform LISS for no longer than 20 minutes at a time. The longer your cardio session, the worse the interference.
- Separate your cardio sessions from your weight training sessions wherever possible. A good guideline is at least 6 hours between cardio and strength training sessions.
- Interference is a mostly localized response. Therefore choose an exercise modality that will target muscle groups that you do not wish to optimize hypertrophy or strength in. For example, competitors in Men’s Physique or Fitness categories that wear board shorts on stage can perform cardio on a stationary bike as thigh and glute development can be compromised. This is not the case however for bikini competitors, who may want to focus on rowing and more upper-body focused forms of cardio.
- Try to perform modalities that involve concentric-only muscle contractions to limit muscle damage. Forms include rowing, cycling, cross-trainer and battle ropes.
- Avoid modalities with high impact forces such as skipping and running as these present a higher risk of injury and muscle and connective tissue damage.
In summary, there are no hard and fast rules when it comes to cardio. The research tells us that both LISS & HIIT can increase energy expenditure and fat burning, both acutely and chronically. However whether to include cardio in someone’s training schedule comes down to the individual and their specific needs.
Here are some scenarios where cardio can be beneficial:
- Overweight/Obese General Population Client Wanting to Lose Weight & Improve Health Markers: If a clients’ goal is not so heavily focused on gaining strength and muscle mass and there is a need to improve health markers, then the implementation of cardio can be highly beneficial. In this scenario, we will not be so overly concerned by the interference effect. Even if weight loss is minimal, obese individuals showing a good level of cardiorespiratory fitness are at reduced risk for cardiovascular mortality (Poirier & Despres, 2001). Walking is an exercise modality that is particularly suitable to the more obese clientele because of the safety, accessibility and popularity.
- High-Stress Corporate Client: Many people find cardio, particularly LISS, is a great way to reduce stress. Modalities such as walking, running and cycling are often found to be almost meditative in a way that resistance training is not. So for clients who are highly stressed and enjoy cardiovascular exercise, including it in their program may be highly beneficial. Walking outdoors is one of my favoured modalities I prescribe to clients as it is not too taxing on the body and exposure to nature has been found in the research to be particularly beneficial for stress management. For example, research has found that walking in forest environments may lower blood pressure by reducing sympathetic nerve activity (Li, et al, 2011).
- Contest Prep. Client Coming into Final Few Weeks: There comes a point where introducing cardio into a contest prep’s clients’ program may be more effective than trying to reduce calories any further. Rather than reduce intake, it may be wiser to increase calorie expenditure. This is only likely to be the case in the final few weeks before a show.
- For fat loss, overall energy balance is more important than substrate oxidization during an exercise session. To that effect, whilst LISS will burn more fat because of it is low intensity and aerobic nature, HIIT has the potential to burn more body fat over a longer time period because of greater energy requirements.
- When assessing whether to use cardio in your training program you must assess what your goals are and whether cardio will assist you in these goals.
- If looking to maximize muscle strength and hypertrophy, cardiovascular exercise should be minimized due to the interference effect
- You can minimize the interference by performing shorter duration bouts utilizing concentric-only modalities that minimize any impact forces such as cycling, rowing, cross-trainer and battle ropes.
- For highly stressed individuals, getting outside in nature and performing some cardiovascular exercise can be extremely beneficial in the management of stress & should be encouraged alongside their regular resistance training routine.
- The more general someone’s goals, the more general the training can be, with the inclusion of different training stimuli and modalities.
Clean Health Fitness Institute
- Jones, T, et al, “Performance and Neuromuscular Adaptations Following Differing Ratios of Concurrent Strength and Endurance Training”, Journal of Strength and Conditioning Research, 2013.
- Wilson, J, et al, “Concurrent Training: A Meta-Analysis Examining Interference of Aerobic and Resistance Exercise”, Journal of Strength and Conditioning Research, 2012.
- Crampes, F, et al, “Effect of Physical Training in Humans on the Response of Isolated Fat Cells to Epinephrine”, Journal of Applied Physiology, 1985.
- Boucher, S, “High Intensity Intermittent Exercise for Fat Loss”, Journal of Obesity, 2011.
- Poirier, P & Jespres, J, “Exercise in Weight Management of Obesity”, Cardiology Clinics, 2001.
- Foster, C, at al, “The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity”, Journal of Sports Science and Medicine, 2015.
- Drenowatz, C, et al, “Change in Energy Expenditure and Physical Activity In Response to Aerobic and Resistance Programs”, Springerplus, 2015.
- Greer, B, et al, “EPOC Comparison Between Isocaloric Bouts of Steady State Aerobic, Intermittent Aerobic, and Resistance Training”, Research Quarterly for Exercise and Sport, 2015.
- De Souza, E, et al, “Effects of Concurrent Strength and Endurance Training on Genes Relating to Myostatin Signaling Pathway and Muscle Fibre Responses”, Journal of Strength and Conditioning Research, 2014.
- Li, Q, et al, “Acute Effects of Walking in Forest Environments on Cardiovascular and Metabolic Parameters”, European Journal of Applied Physiology, 2011.