Strength training for endurance: don't fail by working to failure!

As regular Sports Performance Bulletin readers will know, in recent years there’s been a growing body of evidence demonstrating that the correct use of strength training can improve endurance performance. In particular, studies on runners and cyclists have shown that the use of lower-body, heavy-weight strength exercises can improve muscle economy. In short, this means that muscles become more efficient at converting chemical energy into forward motion, which in turn means that less energy and oxygen is required to sustain a given pace, resulting in less fatigue, especially in longer duration events. The importance of excellent muscle economy can’t be overstated as research shows that excellent economy is a key explanation for the superior performance of top athletes.

The conventional approach for building strength has been to perform sets of exercises targeting the appropriate muscles using enough weight so that while a set of reps can be completed, it is only just possible. In other words, trying to perform another rep with strict form becomes impossible – also known as training to failure. Eagle-eyed readers among you will have noticed however that in Tom Whipple’s recent article on strength training (which you can read here), the emphasis was on NOT training to failure. As Tom explained, this is because some recent research suggests that training to failure is not only unnecessary, it might even be counterproductive. And now,  further evidence indicates that this is indeed the case.

The research

In this study, researchers set out to investigate the effects of a 10-week 'training to failure' resistance programme on strength adaptations in women, and compare it to equivalent training protocols where strength training was not to failure. The 89 subjects were split into three training groups:

1. Three sets of reps, each to failure.
2. Four sets of reps not to failure, but with the volume adjusted (4 sets of 7 reps) to equal that of the ‘train-to-failure’ group.
3. Three sets of reps not to failure (3 sets of 7 reps), which meant that the total volume of work done was less than in groups one and two.

All the groups used the same training exercise (biceps curls) and trained twice per week, with the loading set at 70% of their 1-rep max (maximum amount of weight that can lifted for 1 rep). Standardised strength tests were conducted before, five weeks into, and after the 10-week trial to evaluate the effects of the programmes.

The findings

At five and ten weeks, all of the groups showed significant gains in muscle strength; by the end of the trial, the strength gains for groups 1, 2 and 3 were 28.3%, 26.8% and 28.3% respectively – ie with no significant differences. Likewise, muscular endurance increased similarly across all groups. What was interesting however was that during high-speed movements, peak torque increased ONLY in groups 2 and 3 – ie subjects who didn’t train to failure (by 13.7% and 4.1% respectively).

Another interesting finding was that whereas muscle thickness and bulk increased in the groups 1 and 2 (training to failure and not training to failure but with an equivalent work volume) by 17.5% and 8.5% respectively, there was no significant muscle mass gains in group 3 (not to failure, lower volume). The scientists in the study concluded that their ‘data showed that training of repetitions to failure do not yield additional overall neuromuscular improvements’. Eur J Transl Myol. 2017 Jun 27;27(2):6339. doi: 10.4081/ejtm.2017.6339. eCollection 2017 Jun 24.

Sports Performance Bulletin verdict

This is another study suggesting that for athletes trying to enhance performance, training to failure is NOT recommended. It didn’t build extra strength and it resulted in less peak torque (force) during fast movement than not training to failure. This is important because as an endurance athlete, you want to develop strength that can increase your muscles’ ability to generate force during movement. As endurance athletes, we also want the benefits of increased strength without muscle bulk. So while a bodybuilder will want to train to failure, endurance athletes should not. Indeed, this evidence suggests that a lower volume of work gives all the benefits without building up muscle bulk – exactly as Tom described in his article!

Practical advice

Below are some guidelines on strength training for endurance performance - all based on the best evidence we have to date. However, for a deeper understanding of how to boost your endurance performance with resistance training, see the articles below also!

• Perform strength training that targets the muscles involved in your endurance sport.
• Go heavy on the weight, but drop the reps so that you can complete 4-8 reps without approaching the point of failure (ie you have enough left in the tanks for 2 or 3 more good reps).
• Keep the numbers of sets per muscle group to a minimum; just two or three is sufficient.
• Choose fundamental exercises such as squats, chins, press ups, deadlifts etc as these are better at producing maximal stimulation of the motor system.
• Strength train once (beginners) or twice a week (experienced); any more than this is likely to be counterproductive, and impair your endurance training, especially during the competitive season.