Flywheel training: flying performance for endurance athletes?

Although it may be unfamiliar to most athletes, a new form of strength training known as ‘flywheel’ or ‘inertial’ training is attracting a lot of attention from researchers. With flywheel training (also known as isoinertial or yoyo training) instead of lifting a weight against gravity, you accelerate or decelerate a flywheel (see image above). The potential advantages of flywheel training are that the resistance is variable and unlimited, regardless of the direction or speed of motion. In particular, this allows eccentric overload (high muscle loading during the lowering/muscle lengthening phase of the lift) to be easily achieved – important because eccentric muscle exercise is particularly effective for building strength. But just how effective is inertial training for endurance athletes? Well, a fairly recent study on swimmers provides very persuasive evidence in its favour [Journal European Journal of Sport Science. Volume 17, 2017 - Issue 4, P369-377].

The research

The aim of this study was to evaluate the effects of four weeks of dry-land inertial training on muscle force, muscle power, and swimming performance. Fourteen national-level, competitive swimmers were randomly divided into two groups:

• A control group – who simply continued with their pool training during the 4-week study period.
• The inertial training group – who also continued their normal swim training, but also added in inertial training three times per week. This training was focussed on improving muscle strength required during the upsweep phase of the arm stroke in front crawl and butterfly stroke.

Before and after the 4-week training, all the swimmers underwent testing for their 50m freestyle and 100m butterfly performance. In addition, the inertial trained group underwent muscle-strength and electrical activity testing for the muscles they had trained with the inertial system.

The findings

After four weeks of training, the inertial-trained group recorded a 12.8% increase in their muscle force, and 14.2% increase in muscle power. The control group recorded no gains. But did this translate into improved performance? Well, compared to the control group, the inertial-trained swimmers also significantly improved their pool times, swimming 0.76% and 1.86% faster in the freestyle and butterfly tests respectively. Interestingly, the degree of improvement in each inertial-trained swimmer correlated closely to their strength and power gains Eur J Sport Sci. 2016 Oct 19:1-9. [Epub ahead of print]

Implications for endurance athletes

These results suggest that inertial training is a very effective alternative to conventional weight training. In some environments, the compact size of these inertial units (which can train a wide variety of muscle groups) may offer an advantage – for example, installation by the poolside or in a home gym. And while relatively new, this mode of strength training has support from other recent studies. For example, a study published on inertial training in the previous year found that just one weekly session of inertial training - emphasising eccentric overload - was able to significantly boost lower-limb muscle power in athletes who had previously suffered patella tendon injury to the knee [J Strength Cond Res. 2016 Jul;30(7):1834-42]. Even better, these strength gains occurred without triggering any injury recurrence (something that is all too common with this type of injury).

PRACTICAL SUGGESTIONS

• Inertial training facilities are few and far between at the moment but it might be worth checking in your area to see if anything is available.
• The best training protocol for inertial systems has yet to be established (this is something we will return to in a later issue) but the key seems to be to emphasise eccentric-type movements. Encouragingly, the evidence suggests that just one session per week could be effective.
• Don’t forget that conventional weight training is still a proven performance enhancer. Remember to target the key muscles in your sport. For runners and cyclists, that means calves, thighs and buttocks. Swimmers will need to pay special attention to the chest shoulders and back, emphasising patterns of muscle movement that most closely mimic those used in the swimming stroke.