A new strength-training machine allows the user to instantly change resistance at any point in the exercise movement. The machine has the potential to improve strength by optimizing the time each targeted muscle spends under maximum stress. The benefits for his machine: - The user can change either the positive or negative resistance instantly at any moment during a set or repetition. - If the user learns how to manipulate the resistance properly, s/he will be able to achieve a higher work load during each rep and set. - Casual fitness enthusiasts will therefore be able "…to work out twice as hard and be out of the gym in half the time." - Protocols can be fine tuned to make the training stress more closely match the user's sport-specific requirements. Whether it is more effective than other machines or free weights remains to be seen.