Product Review: Power Development on the Cybex Arc Trainer

The Cybex Arc Trainer has proven time and time again to be an amazing piece in our arsenal of sports performance training equipment. We originally underestimated the piece, classifying it as just another low impact cardio device, but after dozens of studies on thousands of clients, we have found it to be especially effective in enhancing power endurance as well as maximum power in sprinting, running and jump based performances.

The key to unlocking the power of the Arc Trainer is found in the Power Settings (Adaptive Power and Constant Power). These programs often go unused by athletes and trainers due to a lack of understanding on how they work (especially if you are still thinking this machine is just a low impact cardio device). In this brief article I will try to explain how to get the most out of these settings and how we have improved 40 yd dash times, 400 meter times, vertical jumps, standing long jumps, back squat maxes, and just about every type of athletic power for sports performance on the Cybex Arc Trainer.

Power Settings:

A1 Mode – Constant Power

The problem with most equipment that allows the user to control the pace (steppers, bikes, rowers, ellipticals, etc.) is that the user will start off with a strong cadence, and then as fatigue sets in their pace will be slowed (thus losing power). As they approach the end of the interval, the user will increase their pace and finish strong. This undulation of power makes it impossible to track the intensity of the workout, and can give us a false sense of improvement.

To better understand power, we need to know that power is the rate at which we do work or [(mass x acceleration) x distance] / time. To put this in simpler terms, our goal is to move a greater mass/resistance at faster speeds, over more distance in less time. We can do this several ways…

  • Increase the resistance at the same speed = more power
  • Increase the speed at the same resistance = more power

In the past, the difficult part of this was trying to figure out whether to increase the speed or the resistance to improve power. The Constant Power mode takes the guess work out of this decision.

In Constant Power mode the power (in watts) is set at the beginning of the interval, and as the user increases their speed the resistance level drops to hold the power constant. If the user decreases their speed, the resistance is increased to hold the power at the initial setting.  This feature allows the coach to know EXACTLY how much power is being produced over the course of the interval, regardless of the speed the user is moving.

If the user completed the interval, the coach can increase the power setting and know with certainty that the user will be performing a more powerful set, thus making it easy to monitor power increases over time. No more guess work.

Key features:

  1. Since the resistance will increase as speed slows, the Constant Power mode will encourage a FASTER pace over the course of the interval. This faster pace will ensure that the athlete will sustain powerful strides throughout the interval.
  2. Because the power is held constant the tracking and recording of power increases is made simple for the coach, and progress can be monitored and progressed workout to workout.

Another unique application of this set up is that the coach can now look at Cardiovascular and Mechanical Efficiency of the workout. Here is what I mean by this…

Using a heart rate monitor (we use the Polar Team 2 system and/or – pictured below) you can record the peak HR, average HR and HR recovery during the session at a set power level (in watts).  The polar systems give you a Cardio Load or Training Load for the workout (meaning how hard the heart had to work during the workout – times spent in each zone). If you know the mechanical load in watts (your setting on the Arc Trainer), then you can take the mechanical load divided by the cardio load and get an efficiency score.

Example: If you were doing sets of 2 minutes on 1 minute off on the Arc Trainer for 40 minutes at 250 watts this is how you would figure out your efficiency. Working time is the time spent working (subtract your rest time) during the workout.

Watts x Working time = Mechanical Load

Mechanical Load / Cardio Load = Efficiency


(250 Watts) x (26 minutes) / (130) = 50.0 Efficiency

Compare this to someone who was working out at the same power setting (250 watts) but had a higher heart rate (Cardio Load) and you get…

(250 Watts) x (26 minutes) / (158) = 41.1 Efficiency

This is a good way to compare your athletes to see who is more efficient (lower heart rate while still sustaining powerful bursts for longer times), as well as monitor the effectiveness of your conditioning programs on improving the athlete’s efficiency.

A2 Mode – Adaptive Power

The other power-programming mode of the Arc Trainer is the Adaptive Power Training Mode (A2). In this mode, the athlete will choose a level of intensity (1 thru 20) in the beginning of the program. As the athlete increases their speed (in strides per minute) the resistance will increase to intensify the repetition.

Levels 1-5 are fairly easy for an athletic population as the intensity (resistance) is increased slowly and peaks out at a lower level, but levels 6-10 are a little tougher as the intensity comes in a little quicker and the peaks (max power) will hit as high as 900 watts as long as the user can hit and maintain about 165-170 strides per minute. Levels 5-10 are great for intervals of 15-30 seconds or you want the athlete to work as hard as possible for intermediate length power sets.

Levels 11-20 are significantly more difficult as the resistance begins to come in very quickly and peaks out much higher. These levels are better for advanced athletes who are looking for short burst speed and power performances, as the athletes can usually only hold these interval sets for 6-15 seconds before fatigue sets in and power begins to decrease.

Using Adaptive Power on the Arc is even more effective when used in conjunction with power training in the weight room. In fact, we use these types of programs in our workouts as a strength training exercise alongside jump squats, cleans, box jumps and sprints.

We have seen amazing results in the weight room as well as on the field in our speed and conditioning programs after using these two programs. Improved 40 times, vertical jumps, standing long jumps, etc. are just the beginning. When you begin looking at heart rate recovery, interval conditioning and improved aerobic capacity, the Arc seems to be a piece of equipment that can cover the full spectrum. For this reason, we have made it a key piece in our performance program and our athletes are reaping the rewards all season long.

Key Points to Remember on the Interaction between Speed, Incline & Resistance:

  1. Body Weight MUST be entered on every workout, as the Arc’s resistance feedback is actually a percentage of the maximum resistance on the break for your body weight. Failure to do this may make workouts too easy for some, and too hard for others.
  2. Unlike most machines, increasing your incline actually makes the resistance ‘feel’ easier as you get more assistance from gravity, but it may slow down your speed (strides per minute).
  3. Increasing the speed without reducing the resistance will increase the amount of power (in watts) you are generating with every stride.
  4. Increasing the resistance without reducing your speed also increases the amount of power (in watts) you are generating.
  5. Varying the incline during workouts may help to ‘recover’ the legs as it shifts the targeted muscle group, while also gaining assistance from gravity.

For more information on our Arc Trainer Case Studies, you can visit the Cybex Institute website.


  1. I would suggest removing the time ( minutes ) value from the numerator of the efficiency calculation. The following examples will serve this point: ( if we all agree about that the following two performances exhibit the same thermodynamic efficiiency:
    (a) A 260 W effort at 130 beats per minute { for 30 minutes}
    (b) A 260 W effort at 130 beats per minute { for 60 minutes}
    (c) A 260 W effort at 153 beats per minute { 60 minutes}

    Both Case (a) and (b) illustrate that this hypothetical body is capable of generating 2 watts for every beat of the heart. { 2 W/beat}. While it is true that Case (b) indicates that twice the amount of Joules and thus twice the kcals, this has little to due with how efficient the body is converting i thermodynamic energy at the cellular level into mechanical energy . Most exercise physiologists hold that this is somewhere between 15% and 30% . Most what we burn as calories dissipates as heat for metabolic matenance and cooling.

    Both Case (b) and (c) show that the body has produced the same amount of energy { Joules } , but in Case (b) we again have 2 W/beat and in Case (c) only 1.7 W/beat . One would be hard pressed to deny that Case (b) is a more efficient scenario.

    Efficiency is not related to time duration , but level of fitness is. It is interesting to observe through separate time slices , how efficiency deteriorates over time. Recently , I had a 260 Watt effort for 3.5 hours . During the first three hours my efficiency remained consant { 260 W / (145 beat) = 1.79 W/b } . However , during the last 30 minutes , the heart rate increased to 165 beats { 1.58 W/b } . Overall , not a bad effort at 61 years of age.

    1. I see your points, and appreciate your time to comment on this post. Although this is a formula that we continue to tinker with, I still think that duration of sustained power output should be included somewhere. Maybe we shouldn’t call it “Efficiency” and maybe we could come up with a different way of calculating, but to your point at the end of your comment where you stated…

      “It is interesting to observe through separate time slices, how efficiency deteriorates over time.”

      This is really what we want to see…we want to see how long one can perform at a high power output with lower a heart rate. That tells me how “efficient” an athlete can be, and what we can expect from them late in a competitive event.


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