Strength Training: The Evidence
Searching through the recent (last 3 years) of published science on the topic reveals a reasonable level of investigations into the question above. Here I present my brief summary of the findings out there.
Simply put the key peformance criteria for distance running is to be able to run a set distance, whether that be 5000m, 10km or 42.2km faster. Any other change probably isn't really worth it, if it doesn't result in a faster race time. That said, three important variables seem to be highly correalated with endurance race performance:
- Maximal oxygen consumption (VO2max)
- Anaerobic/Lactate/Ventilatory Threshold (AT)
- Running Econcomy (RE)
Does strength training improve race performance, VO2max, AT or RE?
Strength training does not change VO2max or AT. On the other hand it does affect race performance and running economy.
Running Economy (RE)
RE is defined as the steady-rate oxygen uptake measured at a standard running velocity. Improvement in RE for moderate to highly trained runners has been reported to be between 2.8 to 8.1% (average 4.6%), when compared to runners who do not incorporate strength training. The improvements in RE may be due to increased strength improving mechanical efficiency, muscle coordination and motor recruitment patterns. Greater total body strength may to advantageous mechanical changes in running. Increased muscular strength and coordination may reduce the relative intensity of running.
As measured in time trials of 3000m or 5000m improvement in time from 6-14 weeks of strength training has been reported as 2.7 to 3.1%.
I was unable to find a study that directly measured injury rates as related to the inclusion of strength versus no strength training for endurance sports. However, it has been shown to attenuate the reduction of Type I muscle fibres and connective tissue, including increasing the cross-sectional area of tendons. The theory is this is likely to reduce the risk of some types of injuries caused by chronic overload/imbalance like achilles tendinopathy.
Long Distance / Fatigue Resistance
There was no quality studies identified that directly looked at strength training and longer distance running such as marathon or Ironman triathlon. However, one important element of performance at these long distances is the ability to maintain stride length. It has been shown a number of times that a reduction in stride length over a race is directly correlated with fatigue and a slowing of pace. A periodised strength program has been shown to attenuate the loss of stride length during endurance running.
What Type of Strength Program?
The exercises that have come under this heading have been highly varied. Studies that have shown a benefit have included heavy weight lifting at 80+% of 1RM, or a 4RM workloads, short HIIT/explosive circuit style training, plyometrics (jumping, bounding), hill sprints and running with weighted belts. The high variety of different methods is likely to account for a degree of variability in the results. One study was able to show improvement from a periodised program that progressed from straight weightlifting to circuit to plyometrics finishing with running specific resistance exercises when compared to a program that included all these elements evenly spaced through a training period.
My view is training requires a periodised approach that first builds a body capable of handling the training, then increases absolute strength followed by development of specific power.
What Don't We Know?
The timeline used for most studies varied between 6-14 weeks. All studies included runners/endurance athletes that did not regularly include strength work previously. It is well established that the majority of strength/power gains during this time frame for non-regular strength trainers is due to better neuromuscular facilitation. That is the body learns how to better use the muscle motor units. Strength gains through hypertrophy and other means usually follow after this period. Therefore, we do not know exactly what sort of effects (gains or problems) from long term strength training.
Is there an ideal strength level to enhance running? How much strength training should be incorporated each week? Should we include just one type of training or a combination of methods?
Furthermore, no study compared if the time allocated to strength training was simply put towards more running, would there better improvement?
Inclusion of strength training is likely to aid endurance running performance due to an improvement in race times (2.9%) and improved running economy (4.6%) when compared to runners who do not include strength training. Strength training should build absolute maximal strength with heavy lifting and progress to developing power through plyometrics, hill training and dynamic lifts.
Esteve-Lanao J, Rhea MR, Fleck SJ, Lucia A. Running specifc, periodized strength training attenuates loss of stride length during intense endurance running. J Strength Cond Res. 2008;22:1176-1183
Johnston RE, Quinn TJ, Kertzer R, Vroman NB. Strength training in female distance runners; impact on running economy. J Strength Cond Res. 1997;11(4);224-9
Millet GP, Jaouen B, Borrani F, Candau R. Effects of concurrent endurance and strength training on running economy and VO2 kinetics. Med Sci Sports Exerc. 2002;34(8):1351-9
Paavolainen L, Hakkinen K, Hamalainen I, Nummela A, Rusko H. Explosive-strength training improves 5-km running time by improving running economy and muscle power. J Appl Physiol. 1999;86(5): 127-1533
Spurrs RW, Murphy AJ, Watsford ML. The effect of plyometric training on distance running performance. Eur J Apply Physiol. 2003;89:1-7
Storen O, Helgerud J, Stoa EM, Hoff J. Maximal strength training improves running economy in distance runners. Med Sci Sports Exerc. 2008;40(6):1087-1092
Turner AM, Owings M, Schwane JA. Improvement in running economy after 6 weeks of plyometric training. J Strength Cond Res. 2003;17;60-7
Yamamoto LM, Lopez RM, Klau JF, Casa DJ, Kraemer WJ, Maresh CM. The effect of resistance training on endurance distance running performance among highly trained runners: a systematic review. J Strength Cond Res. 2008;22(6):2036-2044