PT on the Net Research

Biofeedback and the De-conditioned Weight Loss Client

At the end of the day, everything we do as personal trainers is a guess. From the exercises we select, to the programs we come up with for our clients, to how we perceive our clients’ mental/emotional states, everything we do is essentially an educated guess. We hope that the core exercise we choose will prevent low back pain or that exercising on an elliptical for 30 minutes will aid in achieving the goal of weight loss and improved cardiovascular health. We validate our choices with anecdotal and scientific evidence, but even this evidence is never 100% conclusive, as we come to realize that each and every individual responds to exercise uniquely.

In her PTontheNet article “Heart Rate Monitoring, Part 1: Taking the Guesswork Out of Training with Biofeedback," author Hayley Hollander discusses how using biofeedback can take much of the guessing out our training programs and help us develop a much stronger understanding of how our client is adapting to our exercise protocols. In this article, we’ll look at a step-by-step approach to using biofeedback for our weight loss clients.

Before we begin, let’s define a weight loss client as someone who is looking to reduce body fat for health or body composition purposes.

Step #1: Assess

All movement requires energy (also known as adenosine triphosphate, or ATP) and our bodies use many energy systems (the ability to convert fat, carbs and protein into ATP) simultaneously to allow us to move with various intensities (Brooks et al., 2000). Based on the intensity and other exercise acute variables (volume, work, rest, etc.), particular energy systems will dominate over other ones and we’ve broken this down into numerous zones or gears. (For more information, watch Scott Hopson and Hayley Hollander discuss gear training.) An example is the anaerobic (ATP-CP) energy system, which is dominant during very high-intensity, short-duration bouts of exercise, while the aerobic fat oxidation energy system is dominant during low-intensity, long-duration exercise. So, thinking logically about our weight loss clients, we want our clients to be exposed to mainly low-intensity, long-duration bouts of exercise. However, this is not very accurate. To claim that the fat oxidative energy system is dominant only during low-intensity, long-duration exercise is to assume that every human engine runs exactly the same (there we go guessing again). In fact, every human engine runs uniquely, which is why we need biofeedback to understand how our engines work.

It is traditionally thought that the fat oxidative system is dominant when the intensity is 0-70% during bouts of movement over two minutes. With the proper training, we can “teach” our body to metabolize fat at higher intensities, even above 90%! (Marcell, et al., 2003). The only way we know this is through biofeedback. Companies such as New Leaf Fitness and iMett offer testing that give us a much clearer understanding of what kind of engine your client currently runs on.

 These tests can:

For simplicity sake, let’s define the anaerobic threshold as the point where a person switches from using the aerobic energy systems (fat and glycolytic oxidative) to anaerobic energy systems (glycolytic/lactate and ATP-CP) (Brooks et al., 2000). In other words, it’s the point in time where the person can no longer buffer the accumulation of lactic acid in the system. This threshold varies greatly from person to person. For the de-conditioned client, it can be as low as 40-50%, where even minimal effort such as walking up one flight of stairs causes a loss of breath and muscle fatigue. The elite endurance athlete may not reach this threshold until above 90% intensity (Klein, 1994). One of the major objectives for the personal trainer in the beginning stages of training is to help the weight loss client achieve a higher anaerobic threshold. In doing so, the client will have improved the ability to metabolize fat at higher intensity and more fat at lower intensity.

Step #2: Improve the Anaerobic Threshold

V02 and anaerobic threshold tests give us a much clearer picture of how our client utilizes fuel. Our next piece of pertinent biofeedback will be the information we receive from a heart rate monitor during the workouts.

In order to drive the anaerobic threshold (AT) higher, both interval and continuous, steady-state exercise can and should be used (Janssen, 2001). As an example, let’s take our typical very de-conditioned weight loss client who reaches AT at 55% intensity.

Table 1: Interval Work for De-conditioned Client

Client's AT % Work:Rest Example Work Duration and Intensity Example Rest Duration and Intensity
55% 1:2 to 1:4 30 seconds at 60 2 minutes at 40%

Using Table 1 as just an example, we can push this person’s anaerobic threshold by simply having him exert enough effort over his threshold for a period of time (in this case 60% intensity of max heart rate for 30 seconds) and then recover until his heart rate lowers well below the threshold. The client can perform interval work for 10-20 minutes as his workout. The great thing here is we can use any form of movement the client enjoys, whether it be traditional cardio training such as walking, jogging or biking, circuit-style strength training or playing with their dog! Biofeedback allows us to use any movement we enjoy so long as we move at the appropriate intensities.

As the weeks progress, so will the client. The client may be able to perform more work at higher intensity and need less time to recover. Work:rest ratios can be progressed to 1:1 or even 2:1 as his fitness improves. Biofeedback from a heart rate monitor will allow us to see this progression happen each workout.

Table 2: Continuous Work for De-conditioned Client

Client's AT % Continuous Training Heart Rate Training Duration
55% 50-54% 30-60 minutes

Maintaining a heart rate just below the anaerobic threshold has been shown to increase a client’s aerobic capacity as well (Londeree, 1997). Using Table 2 as our example, this de-conditioned client may perform continuous work so long as his heart rate stays just below threshold. Most likely this may be a moderate- to fast-paced walk or a moderate bike ride with minimal hills. This can act as a great recovery session as well from a bout of higher-intensity interval training.

Table 3: Example of a Week-by-Week Progression

Week 1

Monday Tuesday Wednesday Thursday Friday
Continuous Off Interval Off Continuous

Week 4

Monday Tuesday Wednesday Thursday Friday
Interval Off Continuous Off Interval

Week 8

Monday Tuesday Wednesday Thursday Friday
Continuous Interval Off Continuous Interval

Both interval and continuous training can be used together and using Table 3, we can see some examples of how this may play out on a week-to-week basis for the de-conditioned weight loss client. As the client’s fitness improves, a reassessment should be done every 4 to 8 weeks to establish a new anaerobic threshold percentage so the appropriate modifications can be made to the training program.

Step 3: Train all of the Gears

To take the guesswork out of training a weight loss client, we first had to establish how our client utilizes fuel using biofeedback from VO2 and AT tests. The second step utilizes biofeedback from heart rate monitors to improve the client’s anaerobic threshold, which will enhance the capacity to metabolize fat at higher intensities. The last step is to make sure our client is improving all 5 training gears.

Gears 1 and 2 are associated with the aerobic energy systems, while gear 3 can be associated with the anaerobic threshold. To maximize our client’s fitness as well as tap into other ways we can help our client lose weight, the client should progress to perform high intensity interval work utilizing the anaerobic gears, 4 and 5 one to three times per week. High intensity training has been shown to have numerous benefits for the weight loss client from increasing metabolic rate, up-regulating anabolic hormones such as growth hormone and IGF-1 (hormones known for their effectiveness on fat metabolism), balancing blood sugar, and simply being able to get an effective workout on a time crunch. (Fraçois, 2008; Edwards, 2008) It’s important to note however, up to this point, we’ve used a de-conditioned client as our example. High intensity training may not be necessary and even risky for the de-conditioned client which is why progression is key and biofeedback gives us vitally important information to see how well the client is progressing. It is advisable to make sure your client is released to train at high intensities by a doctor before attempting high intensity work.

Interval training using gears 4 and 5 will look similar to Table 1, except the work intensities will be much higher – say, above 80% (Gear 4 or 5) - and the rest intensity will be between 60-70% (Gear 1 or 2). A true interval must go above and below the anaerobic threshold. It allows us to train all of our energy systems by using the anaerobic systems to do work and recover with the aerobic systems (PTA Global, 2009).

Maximizing all of the training gears is equivalent to saying the client is maximizing his or her ability to metabolize all fuel sources as well as use the appropriate fuel sources at the right time and intensity. What this means for the weight loss client is a smart approach to not only losing weight but also to maintaining the weight loss with some simple biofeedback while avoiding undertraining and preventing overtraining.

Step 4: Daily Readiness Observation

It is critical to use biofeedback if we want to understand how our clients' bodies respond to stress (exercise). However it’s also important to note that we want to avoid becoming over-technical with our implementation of biofeedback mechanisms. It can be easy to focus solely on the target heart rates we want clients to achieve throughout the workout and forget about many lifestyle factors that can be affecting their stress levels (and thus heart rate readings). Sleep, food, energy drinks, coffee, recovery, volume of training, work, family and even psychological aspects (Horsten et al., 1999) are factors that can greatly affect the heart rate on any given training day. If we are to truly tailor our exercise programs to our clients, we should observe their physical and mental/emotional well-being at the beginning of every session to make the necessary modifications to the exercise program for that session. For example, you may find your client is emotionally distraught, has had little sleep and has a higher resting heart rate is higher than normal. Based on this information, you may decide to switch training gears and have your client play low-moderate intensity games that don’t overstress the system to improve her mental/emotional state instead of the high intensity interval strength and cardiovascular training you had originally planned. Adding more stress to an overstressed system may be the wrong course of action so this kind of daily readiness observation combined with biofeedback allows the trainer to make smart decisions that continue to progress the client towards her fitness goals.

An important lesson here is that biofeedback is designed to be a guide, and not an absolute. Understand who your client is, and what motivates and demotivates him or her. Some clients will appreciate having a target heart rate to achieve during workouts or recovery, while others may actually find it demotivating if they fail at achieving particular heart rates or find themselves competing against others in a small group when they loathe competition. At the end of the day, the client always dictates how you should implement biofeedback during sessions.


A detective must gather clues and evidence in order to solve a crime. Without concrete evidence, the detective can only assume who is guilty of a crime; we’d have a lot of innocent people in jail if this was the way we ran our justice systems. In the case of the weight loss client, the problem is there is too much energy stored as fat in the client’s machine, which has a poor ability to use this fuel source. To solve this case, we must gather evidence as to how this machine utilizes energy using biofeedback (Step 1), maximize their ability to use more fat at higher training intensities (Step 2), and then improve training all of our client’s energy systems with biofeedback as our guide (Step 3), all the while making the necessary session by session modifications to our exercise programs based on the client’s physical and emotional well-being (Step 4). Without biofeedback, we’re like a detective trying to solve a murder case that has no leads, witnesses, nor evidence left behind.


  1. Brooks, G.A., Fahey, T.D., White, T.P. & Baldwin, K.M. (2000). Exercise Physiology: Human Bioenergetics and Its Application, 3rd edition. Mountain View, CA: Mayfield Publishing Company.
  2. Edwards, S. (2008, March 14) HR and Anaerobic Intervals. Retrieved from
  3. François, P., Bernard, G., Ruddy, R. et al. (2008). Training at high exercise intensity promotes qualitative skeletal muscle adaptations of mitochondrial function in human. J Appl Physiol 104: 1436-1441.
  4. Horsten, M., Ericson, M., Perski, A., Wamala, S., Schenck-Gustafsson, K. & Orth-Gomér, K. (1999). Psychosocial Factors and Heart Rate Variability in Healthy Women. Psychosomatic Medicine 61(1): 49-57.
  5. Janssen, P. (2001). Lactate Threshold Training. Champagne, IL: Human Kinetics.
  6. Klein, S., Coyle, E.F. & Wolfe, R.R. (1994). Fat metabolism during low-intensity exercise in endurance-trained and untrained men. Am J Physiol Endocrinol Metab 267: E934–E940.
  7. Londeree, B.R. (1997, June). Effect of training on lactate/ventilatory thresholds: a meta-analysis. Medicine & Science in Sports & Exercise, 29 (6): 837-843.
  8. Marcell, T.J., Hawkings, S.A., Tarpenning, K.M., Hyslop, D.M., & Wiswell, R.A. (2003). Longitudinal Analysis of Lactate Threshold in Male and Female Master Athletes. Med. Sci. Sports Exerc., Vol. 35, No. 5: 810-817.