Speedflex machines give a high-intensity workout without the next-day soreness

Feel the burn: Linda gets started on her squats (Frantzesco Kangaris)

The sight of a room full of Speedflex machines is almost enough to make one walk away in terror. But, as ever, the greatest thing to fear is fear itself. And squats. Lots of squats.

It may look daunting, but Speedflex does the good of a high-intensity workout without the next-day soreness. Afterwards I could actually walk up the stairs and carry shopping bags painlessly. Result.

The training involves a circuit of five customised machines in a 30- or 45-minute group session, each machine operates on one plane, up and down, and each has a different purpose. They are weight-free and create resistance based on your own force. Plus, they have zero risk of injury, which is why some people use it as part of post-injury physio.

Developed in 2009 in the USA by a team including former baseball pro Darren Holmes, the workout combines cardio with resistance training. It improves muscle tone, enhances power and speed, and you can burn up to 800 calories in one session (I burnt 600). Forget about bulky muscles and think of a lean, fit silhouette.

In addition, circuits include medicine balls, kettlebell exercises, jumps and burpees as the interval between each machine. The fee includes a health screening, body composition analysis and blood chemistry test. Then, during the session, a heart-rate monitor around your chest tracks the progress throughout. As you're breathless while doing the squats or steps-ups on the machines, screens around the room indicate your heart-rate level.

It's an exciting, albeit expensive, alternative to a regular gym.

Cheapskate's version: Find a double spring see-saw and lift/lower.

Price: Single sessions, £30; £150 monthly. The UK studio is based in Bank, London EC3; speedflex.com