The Golden Ratio

Cable machines are a versatile piece of resistance training equipment that enable a significant range of muscle strengthening and rehabilitation exercises.  If you are thinking of investing in a cable machine one of the key specifications to consider is the cable ratio.
Summary:The cable ratio determines the actual resistance on a cable machine
Higher cable ratio number = lower overall resistance but smaller increments between weight plates
Higher cable ratio = longer cable than lower cable ratio (a 2:1 cable is twice the length of a 1:1 cable)
Divide the weight on the stack by the first number in the cable ratio to know the actual resistance of a cable machine

In short, the cable ratio explains the difference between the weight selected on the weight stack and the actual resistance at the end of the handle experienced by the person lifting. The first number in the cable ratio represents the actual resistance, while the second number represents the amount of weight selected on the stack. To calculate the actual resistance divide the amount of weight selected on the stack by the first number in the ratio.

For example, a weight stack with 50 kg selected and fitted with a 2:1 ratio cable produces 25 kg of resistance (50 kg / 2 = 25 kg).  It follows that a 3:1 cable at 50 kg produces 16.67 kg of resistance, while with a 1:1 cable 50 kg produces 50 kg of resistance.

To use the example of a 50 kg weight again, with a 2:1 ratio cable a single handle extension has a resistance of 12.5 kg (50 / (2*2) = 12.5 kg).  For a 3:1 cable, a single handle extension at 50 kg produces 8.33 kg of resistance, with a 1:1 cable 50 kg produces 25 kg of resistance.

The bad news is that you might not be as strong as you thought!  Typically cable machines in commercial gyms have a cable ratio of 3:1.  However, those 50 kg bicep curls still look impressive to the uninitiated.

In practical terms, a higher ratio cable is longer and passes through more pulleys than a lower ratio cable - a 2:1 cable is twice the length of a 1:1 cable.  This means that the higher the ratio of the cable the shorter the distance that a weight stack moves during a specific exercise and therefore the less force that is required to perform an exercise.  Makes sense if you remember GCSE physics, if not more information on the science behind pulleys can be read here.

The advantage of a higher ratio is that there are smaller increments between each weight plate.  A further advantage is that the increased length of a higher ratio cable allows for exercises to be performed with the handle further away from the cable machine.  On the NOHrD SlimBeam the 3:1 ratio cable extends up to 8 m from the machine, ideal for walking lunges.  In contrast, a lower ratio cable provides greater resistance.  Ideal for high-performance athletes and those looking to build significant strength and muscle mass.

The NOHrD SlimBeam has a 75 kg weight stack (14 x 5 kg plates + 1 x 5 kg base plate) with the option of either a 3:1, 2:1 or 1:1 cable to suit different user preferences and exercises. The table below shows the range of actual resistance with each cable on the SlimBeam.

A 3:1 cable ratio suits users that are looking to lift lighter weights and would like smaller increments between weight plates. Ideal for rehabilitation or those that are new to resistance training.

2:1 cable ratio provides enough weight for most people while still offering reasonably smaller increments between plates.

1:1 cable ratio, suitable for athletes, bodybuilders, and those aspiring in that direction. Move over Arnold Schwarzenegger!