Strength for endurance: in it for the long term?

Does strength training practiced over years rather than weeks or months produce even greater performance gains in the longer term?

As regular SPB subscribers will know, a great deal of evidence has accumulated in recent years demonstrating the benefits of strength training for athletes – not just strength and power athletes, but endurance athletes too, such as those competing in distance running and cycling events^(1-3). The traditional view of strength training in endurance sport is that it helps by improving resilience and reducing injury risk, which is certainly true enough⁽⁴⁾.

However, it has also become increasingly apparent that heavy strength training can benefit muscle economy⁽⁵⁾. In short, this means that muscles become more efficient at converting chemical energy into 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 benefit of improved muscle economy cannot be overstated in endurance sports because research shows that excellent economy is a key factor for the superior performance of elite distance athletes⁽⁶⁾.

Multiple sprint/acceleration ability

Improved muscle efficiency and reduced injury risk are great reasons for endurance athletes to strength train. However, there’s also another incredibly important reason: sprinting and acceleration capacity. Although often underappreciated, the ability to repeatedly turn on bursts of power, sprints, or to accelerate plays a very important role in determining performance at elite levels of competition. In many endurance sports, the sprint performance and anaerobic capacity of an endurance athlete can be crucial for performance (see this article to highlight its importance in pro cycling). Examples of studies demonstrating the importance of power, acceleration and sprint ability include:

• Research into the changes in exercise intensity and multiple accelerations during an Olympic road racing with a closed-circuit criterium style^(7,8).
• Data on the final sprint toward the finish line or during a race in sports such as cross-country Olympic mountain biking⁽⁹⁾.
• During cross-country skiing⁽¹⁰⁾.

These findings are perhaps not unexpected as a number of studies have repeatedly shown that heavy strength training increases cycling sprinting power in endurance athletes such as cyclists^(11-14). The conclusion is therefore that heavy strength training should also play an integral part of a training program in endurance athletes whose sports require burst of acceleration or power, either occasionally or repeatedly.

Long-term heavy strength training

Although we know that a period of heavy strength training seriously benefits strength, power and acceleration what we don’t know is whether prolonged use of heavy strength training over several seasons results in progressively greater gains as time passes? The reason we don’t know is that nearly every strength-training intervention study that has been carried out has been for a limited period of time of a few weeks (mostly due to time and money constraints), after which data is gathered and conclusions drawn. In the studies above, the duration ranged from 10 to 25 weeks, which, from a perspective of a 4-year Olympic cycle, is actually very short-term duration. In short, there is a lack of data on the effect of continuing heavy strength training across several competition seasons and preparatory periods on elite endurance athletes such as cyclists.

Multi-season strength training

Although no studies to date have investigated the effects of multi seasons of heavy strength training on acceleration, power and sprinting ability in endurance athlete, a brand new case study published in the journal ‘Frontiers in Sport and Active Living’ provides a fascinating insight into the long-term effects of strength training over several seasons⁽¹⁵⁾.

In the study, researchers analyzed muscle strength and cycling sprint power data from four elite cross-country mountain bike cyclists who maintained a similar volume of endurance training but where the strength training practices varied. Two of these cyclists performed heavy strength training HST across two preparatory periods (spanning two years), while the two other cyclists continued with similar endurance training to the two first cyclists except they performed no strength training.

Following this period of time, one of the two heavy strength-training cyclists continued with heavy strength training for two more years (years 3 and 4). Meanwhile, one of the two cyclists who had not performed any heavy strength training in the first two years then started strength training and continued for the next two seasons (ie years 3 and 4). This study therefore compared the development of muscle strength and cycling sprint power in an elite cyclist who performed strength training continuously for four years with another cyclist who performed it for the first two years, a third who performed it in years three and four and one cyclist who performed no heavy strength training at all. The results were as follows (see figure 1):

• The two cyclists who heavy strength trained experience a mean increase in leg press force and cycling sprint power of 16% after the first preparatory period (November to April), which was maintained during the competition period.
• After the next preparatory period a further increase from the first test was achieved by these cyclists (22 and 19%, respectively).
• The two cyclists who didn’t strength train experienced no gains in leg press force and cycling sprint power.
• The cyclist who continued with heavy strength training for two more years achieved a continuous increase in leg press force during all four preparatory periods, ending up with a total increase of 44% after 3.5 years (while the development of cycling sprint power had more variation, with an apparent plateau from the third to fourth preparatory periods, ending up with an improvement of 25%).
• The cyclist who did no heavy strength work in years 1-2 then switched to performing strength training in years 3-4 experienced an increase in leg press force and cycling sprint power of 24% and 22% respectively – showing that regardless of when the strength work was started, the gains were similar!

The researchers concluded that their findings show heavy strength training can give reasonable and cumulative muscle strength improvements in elite cyclists across multiple preparatory periods, and also that these benefits can be maintained across multiple competition periods.

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Figure 1: Effects of heavy strength training across multiple seasons

E1/E2 (open squares and triangles) = endurance-only cyclists; E&S1/E&S2 (black squares and triangles) = endurance + heavy strength work. Over the first two seasons, the strength-trained cyclists experienced a significant gain in leg press force and power, and 6-second sprint power, whereas the endurance-only cyclists did not.

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Practical implications for athletes

The first thing to say is that the evidence from this research derives from case studies of cyclists rather than a carefully constructed randomized controlled trial. Given that data from case studies is less robust than that from controlled trials, we must be somewhat cautious. Furthermore, the cycling outcome measured was maximum 6-second cycling power rather than aerobic endurance performance. However, we know from data that the ability to produce power and acceleration IS very important in many endurance sports. Also, it’s also the only long-term data we have to go on!

Taking a rounded view, the real take-home message here seems to be that endurance athletes who strength train during the preparation period of a season can expect sprint/power/acceleration gains later on in that season. But even better, if they also strength train in seasons two and three, they can expect additional and cumulative gains in power/sprinting ability in those seasons. After three consecutive seasons of strength training, it’s harder to say whether there might be further gains but athletes can at least expect to maintain their well-won gains. Overall then, it seems that if the ability to sprint, accelerate or sustain high bursts of power is important in your sport, it’s worth taking a long-term approach to strength training!

References

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15. Front Sports Act Living. 2022; Apr 25th (4)860685