Hello and welcome to Research Pod! Thank you for listening and joining us today. In this episode we learn more about the research of Professor Kjell Hausken at the University of Stavanger, evaluating the energy expenditure from different types of exercise classes.
Which type of exercise is best? While the answer is highly subjective, it is helpful for trainers, coaches and their clients to be able to compare different forms of exercise. One way to do this is to look at energy expenditure.
Professor Kjell Hausken of the University of Stavanger, Norway, led a study of a particular type of exercise class that included both aerobic and weightlifting exercises. The resulting insights into energy expenditure allowed Professor Hausken to develop a framework for evaluating different types of exercise classes.
It is safe to say that 2020 has been an unusual year. For many people around the world, one indirect consequence of the COVID-19 pandemic has been chances to exercise. Stuck at home for weeks or months, finding the motivation or opportunity for exercise has been challenging for many. But, as lockdowns lift and gyms re-open, many people might be looking to re-gain their previous level of fitness or even make a “fresh start”.
While everyone has their own reason for exercising, their own goals and desired outcomes, for many the motivations are similar: losing weight, building muscle, enhancing aerobic capacity, or all these. So, how can people choose the best exercise for them, one that will put them on the path towards achieving their goals? One popular option is to attend structured exercise classes led by a qualified trainer. There are many from which to choose: from boxercise and spin classes to high-intensity interval training (HIIT) and group strength training sessions.
For trainers, designing an exercise programme that helps clients – whether individuals or groups – to achieve their exercise goals is vital. An hour’s structured exercise class, for example, should guide the client to use their energy in the most effective way, whether that is primarily through aerobic exercise, strength training, or a combination of the two. To determine how to do this, an understanding of the energy expenditure during different types of exercise is needed.
To investigate energy expenditure during structured exercise, Professor Kjell Hausken of the University of Stavanger, and his co-author Ms Anne Tomasgaard, focused on one specific type of exercise class.
Performance Step Interval is a 75-minute class, mostly comprised of alternating step aerobics and weightlifting segments, interspersed with individual balance, standard aerobic and abdominal/back strengthening activities. The class is designed time efficiently to maximise aerobic activity, while also building muscular strength. The interval-based format of the class is intended to help participants to maintain motivation and focus throughout the segments.
A Performance Step Interval class includes three step aerobics segments altogether, decreasing in length from 15 to 10 to 5 minutes. The first is the most challenging in terms of choreography (on the basis that participants are most rested at that stage), while the others are simpler. All, however, represent an “explosive” form of exercise, using the powerful but quick-to-tire “fast twitch” muscle fibres.
For the three weightlifting parts of the class, participants select their own weights based on their individual goals and abilities. The first weightlifting session focuses on large muscles, such as those of the thighs and lower legs, via exercises including squats and bench press. In the second, participants work on the back and triceps, and in the third segment perform exercises to target the biceps and deltoids (shoulders). Weightlifting uses the fatigue-resistant “slow twitch” muscle fibres, while allowing the fast-twitch fibres to recover.
Professor Hausken recorded the heart rates of ten participants every 15 seconds over the course of the 75-minute class. Each person’s weight, age and sex were also noted (all participants were women aged in their 20s and 30s), as these factors can all influence energy expenditure. The researchers aimed to use the data to test several hypotheses, including that the participants’ heart rates and energy expenditure would be higher during aerobics than during weightlifting and that Performance Step Interval is as effective, in terms of energy expenditure, as running at a little over 8km/hour.
Normally, a person’s heart rate will be higher during aerobic exercise than during weightlifting/strength training. In the case of a Performance Step Interval class, however, the researchers expected that the alternation of the two different types of training would cause participants’ heart rates to “average out” to a certain extent.
The higher heart rate reached during an aerobic segment could be expected to persist, for a short time, into the subsequent weightlifting activity; on the other hand, participants would recover to an extent during weightlifting, therefore starting the next aerobic part with a lower heart rate.
The results showed that this is, in fact, exactly what happens during Performance Step Interval. The difference in both energy expenditure and heart rate between the aerobics and weightlifting
segments is reduced by the interval-based training. To confirm this finding, the researchers compared their results with studies that looked at one type of training alone. In classes which focus on a single form of training, a similar heart rate tends to be maintained throughout: higher for aerobic work and lower for weight training.
Professor Hausken also found that, as expected, the energy expenditure of a Performance Step Interval class as a whole is equivalent to running at just over 8km/hour. Perhaps surprisingly, the weightlifting segments alone actually have a slightly higher energy expenditure, equivalent to running at between 8.05km per hour and 8.37km per hour. The aerobics segments are equivalent to running at 8.37km per hour. This suggests that the lower average energy expenditure of the class as a whole is due to the other sections, which include balance and stretching activities.
The main ultimate goal of Professor Hausken’s study was to develop practical advice that could be used by trainers and coaches to develop effective exercise programmes for their clients. The results of this research offer important insights into the potential benefits of combining different forms of exercise in the same class, as in Performance Step Interval.
Firstly, Professor Hausken has created a useful framework for evaluating and comparing different types of exercise class. So many options are now available for people seeking an exercise class that it can be difficult to know where to start. Information such as the relative energy expenditure of different classes could help trainers to guide their clients towards the most suitable class for their particular needs.
This research also shows how it is possible to evaluate an exercise class comprising numerous different activities. Approaching the design of a class in this way allows trainers to test different combinations and sequences of activities, which can be tailored to meet particular objectives.
Professor Hausken gives the example of a segment demanding complicated choreography or precise technical skills; in this case, the energy expenditure of the preceding segment could be reduced, to ensure participants would be energised and focused for the more demanding activity. In addition, this study demonstrated that comparing the energy expenditure of various exercises, as in this study, with jogging at particular speeds, is a useful way to help trainers and their clients understand the demand of particular activities.
In this research, Professor Hausken used wristwatch-type heart rate monitors to measure participants’ heart rates during the class. These devices proved to be a convenient and effective way to assess energy expenditure, which was calculated using a formula based on age, weight and heart rate. Similar heart rate monitors are relatively inexpensive and available in many gyms, meaning that they could be a simple way for trainers and participants to keep track of energy expenditure during exercise. In the subsequent studies with Dr Sindre M. Dyrstad both heart rate monitors and accelerometers (attached to one’s hip) were used.
Performance Step Interval is designed with a quick increase in heart rate in the first step aerobics segment, boosting metabolism which persists through the strength training segments while the heart rate decreases, and increases in the subsequent step aerobics segment.
One unique aspect of Performance Step Interval is the demanding coordination through more complex choreography in the first step aerobics segment, which trains the eye - muscle response, which is highly useful in daily life (e.g. when moving in the supermarket), and which some trainers may miss when working with clients.
Finally, the concept demonstrated in this research shows how exercise programmes can be effectively tailored and even personalised to an individual’s goals and preferences, whether that is better cardiovascular fitness, fat loss, improved flexibility, stronger and more toned muscles, greater stamina or simply a general desire for better physical health to face the challenges ahead.
That’s all for this episode – thanks for listening, and stay subscribed to Research Pod for more of the latest science. See you again soon.