If you want to become faster and more agile it’s worth adding resisted sprints to your training: 20 to 40 metre sprints that are made more difficult by pulling a weighted sled behind you. The amount of weight on the sled determines the aspect of acceleration capacity that you train, write sports scientists at Pablo de Olavide University in Spain in an article that will soon appear in the Journal of Strength and Conditioning Research.
Trainers of athletes that do team sports and martial arts have been using resisted sprint training for decades to improve their athletes’ acceleration capacity. Reading the literature you’ll learn that the method is most useful for increasing athletes’ speed in the first 20 metres of a sprint.
The researchers at Pablo de Olavide University wondered whether it made any difference the amount of weight there was on the sled so they did an experiment with 19 male student subjects. All subjects trained twice a week with a weighted sled for a period of seven weeks. They did 4-8 sprints, with distances varying from 20 to 35 metres. The students rested for 3-4 minutes between sprints.
The researchers divided the students into three groups. The first group trained with a sled that had been weighted with 5 percent of the subjects’ bodyweight [LL], the second group trained with 12.5 percent of their bodyweight [ML] and the third group with 20 percent of their bodyweight [HL].
Before and after the training period the researchers timed how fast the students could run 40 metres. They discovered that for the whole distance of 40 metres it made no difference which weight the students had trained with.
But when they looked at the effect of the training on the first 20 metres, they noticed that only the subjects that had trained with the heaviest weight had become faster.
When the researchers looked at the effect on the last 20 metres, only the subjects who had trained with 5 and 12.5 percent of their bodyweight showed better times.
“The results of our study would suggest that in order to improve the acceleration phase over short distances it is advisable to train with different towed loads”, the researchers summarise.
“To improve the initial acceleration phase up to 30 meter, it would be advisable to train with loads about 20 percent of body mass. However, to improve the flying phases within 40 meter, loads between 5 percent and 12.5 percent should be used.”
Effects of resisted sprint training on acceleration with three different loads accounting for 5%, 12.5% and 20% of body mass.
The optimal resisted load for sprint training has not been established yet, although it has been suggested that a resistance reducing the athlete’s velocity by more than 10% from unloaded sprinting would entail substantial changes in the athlete’s sprinting mechanics. This investigation has evaluated the effects of a 7-week, 14-session sled resisted sprint training on acceleration with three different loads according to a % of body mass (BM): low load (LL: 5% BM, n = 7), medium load (ML: 12.5% BM, n = 6) and high load (HL: 20% BM, n = 6), in young male students. Besides, the effects on untrained exercises: vertical jump (CMJ), loaded vertical jump (JS) and full squat (SQ) were analyzed. The three groups followed the same training program consisting in maximal effort sprint accelerations with the respective loads assigned. Significant differences between groups only occurred between LL and ML in CMJ (p<0.05), favoring ML. Paired t-tests demonstrated statistical improvements in 0-40 m sprint times for the three groups (p<0.05), and in 0-20 m (p<0.05) and 0-30 m (p<0.01) sprint times for HL. Sprint times in 10-40 m (p<0.01) and 20-40 m (p<0.05) were improved in LL. Time intervals in 20-30 m and 20-40 m (p<0.05) were statistically reduced in ML. As regards the untrained exercises, CMJ and SQ for ML and HL (p<0.05) and JS for HL were improved. The results show that, depending on the magnitude of load used, the related effects will be attained in different phases of the 40 m. It would seem that to improve the initial phase of acceleration up to 30 m, loads around 20% of BM should be used, whereas to improve high-speed acceleration phases, loads around 5 to 12.5% of BM should be preferred. Moreover, sprint resisted training with ML and HL would enhance vertical jump and leg strength in moderately trained subjects.
PMID: 24736770 [PubMed – as supplied by publisher]