“Wake up, wake up, wake up, it’s the first of the month, to get up, so cash your checks and get up.”
If you have heard the popular rap lyrics before, you can understand how exciting the first of the month can be. For political reasons, I won’t get too far into Bone Thugs enjoyment of that particular day…. but I have a great and completely different reason for enjoying the first; I get the new edition of Strength and Conditioning Research!
This tool in my educational process really helps me stay on top of the latest and greatest in the sport science field. You can check this service out for yourself at:
strengthandconditioningresearch.com.
With that said, I use Bret and Chris’s compilation, which neatly summarizes the best 50 research studies of the last month, to stay on top of things in this industry. There was so much good research this past month, it was really difficult to put my top three on the list! After some deliberation, here are my top three studies.
- Why hamstring eccentrics are hamstring essentials. Thorborg, in British Journal of Sports Medicine, 2012
- Meta-Analysis of Post Activation Potentiation and Power: Effects of Conditioning Activity, Volume, Gender, Rest Periods, and Training Status. Wilson, Jacob M.; Duncan, Nevine M.; M Marin, Pedro J.; Brown, Lee E.; Loenneke, Jeremy P.; Wilson, Stephanie M.C.; Jo, Edward; Lowery, Ryan P.; Ugrinowitsch, Carlos
- Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. Tim Dorn, Anthony Schache and Marcus Pandy.
Study #1.
Why hamstring eccentrics are hamstring essentials
Thorborg, in British Journal of Sports Medicine, 2012
You can find the full publication here: http://bjsportmed.com/content/46/7/463.full
Discussion: In a nutshell, this study took advantage of some prior studies that have been mentioning how effective eccentric work may be for preventing hamstring injuries. Hamstring pulls are a nightmare for any sport coach, and especially track coaches. I am always looking for ways to keep my athlete’s hamstrings healthy. Two things I have picked up in the last year have been mandatory soft tissue work prior to practice via softballs/lacrosse balls, and then a higher priority on glute strengthening. After seeing the results of this study, you can bet that next year, eccentrically based hamstring work in full ranges of motion will also be in there. Here are some details of the study and why I will be including this in my athlete’s training.
When athletes pull a hamstring, it takes a long time, on average, to get that hamstring back to full strength. Research is cited in this study that showed that levels are only around 90% at 6 weeks post-injury and it took 16 weeks to return to full strength. Because of the length of this time frame, Thorborg proposed that the focus of rehab needs to be on replicating the function of the hamstrings, rather than the amount of time it takes to restore full strength.
In regards to hamstring function, there have been some excellent recent findings. One idea has been that eccentric based hamstring work will cause the highest amount of torques the hamstring can produce to be at it’s longer ranges of motion, rather than shorter ranges. Many hamstring pulls and tears occur directly before ground contact in the sprinting motion, when the hamstring is in an elongated state. Because of this, it makes sense that working hamstrings hard eccentrically through a full range of motion can help build strength and maximal torque in the range where the pulls may occur.
For Thorborg’s study, data was collected from 942 soccer players. It was found that putting players on a 10-week rehabilitation program of Nordic Hamstring Curls caused a reduction in hamstring re-injuries by 70%! (The Nordic Hamstring Curl is a eccentric natural glute-ham raise, http://www.youtube.com/watch?v=XGQ7NFG0x3o)
Based on this study, I would strongly recommend the inclusion of some full-length eccentric based work for hamstrings into your own training program, whether that be through the Nordic Curl, Glute-Ham, Romanian Deadlift, or standard leg curl. Another nice trick to maximize the eccentric output of each exercise can be to use two legs for the concentric portion, and then only one leg for the way down. For example, if you were using a lying hamstring curl on a machine, you would lift the weight concentrically (up) with two legs, and then take a leg away to lower the weight with only the other leg. Hopefully, we will see a vast reduction in hamstring pulls in athletes in the near future with this method.
Study #2.
Meta-Analysis of Post Activation Potentiation and Power: Effects of Conditioning Activity, Volume, Gender, Rest Periods, and Training Status
Wilson, Jacob M.; Duncan, Nevine M.; Marin, Pedro J.; Brown, Lee E.; Loenneke, Jeremy P.; Wilson, Stephanie M.C.; Jo, Edward; Lowery, Ryan P.; Ugrinowitsch, Carlos
Journal of Strength and Conditioning Research, Published ahead of print.
Abstract: There is no clear agreement regarding the ideal combination of factors needed to optimize Post Activation Potentiation (PAP) following a conditioning activity. Therefore a meta analysis was conducted to evaluate the effects of training status, volume, rest period length, conditioning activity, and gender on power augmentation due to PAP. A total of 141 Effect Sizes (ES) for muscular power were obtained from a total of 32 primary studies, which met our criteria of investigating the effects of a heavy pre conditioning activity on power in randomized human trials. The mean overall ES for muscle power was 0.38 following a conditioning activity (p < 0.05). Significant differences were found between moderate intensity (60-84 %) 1.06 and heavy intensity (>85 %) 0.31 (P < 0.05). There were overall significant differences found between single sets 0.24 and multiple sets 0.66 (P < 0.05). Rest periods of 7-10 minutes (0.7) following a conditioning activity resulted in greater ES than 3-7 minutes (0.54), which was greater than rest periods of >10 minutes (0.02) (P < 0.05). Significant differences were found between untrained 0.14 and athletes 0.81, as well as between trained 0.29 and athletes. The primary findings of this study were that a conditioning activity augmented power output, and these effects increased with training experience, but did not differ significantly between genders. Moreover, potentiation was optimal following multiple (vs. single) sets, performed at moderate intensities, and using moderate rest periods lengths (7-10 minutes).
Discussion: Complex training (PAP, or “Post-Activation-Potentiation”) is talked about a lot in training circles. Example of PAP: Perform 3 reps on the squat with 80% of your 1RM as fast as possible, and use this exercise to “supercharge” your CNS. Use the charge to boost performance on a dynamic exercise you perform 1-15 minutes later, such as maximal vertical jumps, plyometrics, or sprinting. Some hold complex training as a mystic key to unlocking athletic development, and many vertical jump programs you can buy online are littered with this type of training. So is it any good? I have looked for meta-analysis on this type of training in the past, and this current study is as good as it gets for the proper utilization of this method.
In terms of athletes best suited for complex training, the researcher found that athletes with more than 3 years of resistance training experience appear to respond optimally to this type of work.Regarding the intensity of the coupled strength exercise, lower intensities are found to be better than high ones. This intensity is to the tune of 60-84% of the 1RM, rather than the very high intensities that some sources advocate.High intensities, such as 85+% will be nice for nervous system stimulation, but awful when it comes to mechanical trauma on the body that will reduce the effectiveness of whatever speed based exercise is tied on. Lighter weights work better than really heavy ones in PAP.
Athletes with more training experience were found to respond better to complex training, and also were found to respond better to greater volume in terms of multiple sets of this type of effort. Beginners were better suited to lower sets, as they experienced reductions in power through repetitive versions of complex sets. An important key to remember when working speed and power is not to let the power drop; you don’t get fast by training slow!
In summary, complex training making use of “PAP” can be a useful tool in a coaches toolbox, but it can be the best when using moderate weights and sets appropriate to the current level of the athlete. The researchers also suggested 7-10 minute rest breaks between the “potentiator” and the speed based exercise. I can guarantee that this is NOT practiced by 95% of all PAP trainees.
So, lower the weight a bit, don’t let the power drop, and wait a good 7-10 minutes between strength and speed efforts, and see what PAP can do for you! Hopefully this is only the beginning of more good insight into this training methodology.
Study #3.
Tim W. Dorn, Anthony G. Schache and Marcus G. Pandy J Exp Biol 215, 1944-1956
Abstract: Humans run faster by increasing a combination of stride length and stride frequency. In slow and medium-paced running, stride length is increased by exerting larger support forces during ground contact, whereas in fast running and sprinting, stride frequency is increased by swinging the legs more rapidly through the air. Many studies have investigated the mechanics of human running, yet little is known about how the individual leg muscles accelerate the joints and centre of mass during this task. The aim of this study was to describe and explain the synergistic actions of the individual leg muscles over a wide range of running speeds, from slow running to maximal sprinting. Experimental gait data from nine subjects were combined with a detailed computer model of the musculoskeletal system to determine the forces developed by the leg muscles at different running speeds. For speeds up to 7 m s–1, the ankle plantar flexors, soleus and gastrocnemius, contributed most significantly to vertical support forces and hence increases in stride length. At speeds greater than 7 m s–1, these muscles shortened at relatively high velocities and had less time to generate the forces needed for support. Thus, above 7 m s–1, the strategy used to increase running speed shifted to the goal of increasing stride frequency. The hip muscles, primarily the iliopsoas, gluteus maximus and hamstrings, achieved this goal by accelerating the hip and knee joints more vigorously during swing. These findings provide insight into the strategies used by the leg muscles to maximise running performance and have implications for the design of athletic training programs.
Discussion: A study by Matt Brughelli that came out a couple of years ago really turned some heads in terms of learning which muscles and forces really contribute to top-end speed development. In Brughelli’s landmark study, it was found that when moving from a jog to a sprint, the horizontal forces increase markedly, but the vertical forces increased by fairly little. Bottom line of the study, train the muscles responsible for horizontal force development if you want breakaway speed! These muscles would be the glutes and hamstrings.
In this study, the researchers took a new approach to determining how changing from a jog to a sprint changes muscle and force contributions, and also threw in the aspect of the ankle performance. This study used an actual track in which to collect the data, along with computer modeling, so many of the “haters” of prior studies (which were done on treadmills) may have less to criticize regarding this study and it’s relevance. Instrumentation in this study included a 3d motion capture system and reflective markers (near and dear to my heart), force plates spaced out on the track, and EMG.
The results of this study found similar results to Brughelli’s treadmill study. In going from 3.5m/s to 7.0m/s all muscle groups increased in force production and EMG activity. The transition from 7.0m/s to 9.0m/s was where things transitioned to the dominance of horizontal force at this speed. Vertical support forces in this study increased by around 33% when making the jog (3.5m/s) to light sprint (7.0m/s) transition, but those forces did not increase at all when moving to an near maximal sprint at 9.0m/s. The gastroc, soleus and vasti muscles of the quads were found to provide 75% of the vertical support forces during sprinting.
The action of the horizontal forces when moving from 7.0m/s to 9.0m/s were a different story! When calculating the force production of the glute and hamstring, both muscles force output doubled when moving from the light sprint to near-maximal effort. The hamstring muscle was taxed the most, working at a force of 9x bodyweight at the high speed sprint! The researchers also found the strength of the iliopsoas muscle group to be of massive importance during the swinging action of the leg during sprinting. No wonder sprinters like Asafa Powell have such huge hip flexor muscles! If you have read Jimson Lee’s report on Jamaican sprinting, you will find that they often end their workouts with running
The researchers conclusion of the study was that maximal sprint velocities rely heavily on the glutes, hamstrings, and hip flexors; not the quads or calves. If you want to get blazing speed, you need to be paying attention to your posterior chain and hip flexors in your strength development. My new favorites, as I have stated before are the hip thrust and glute bridges. Although running high knees is old school, I recommend those as well, based on this study.
Comparing Iliopsoas groups between an elite sprinter (Asafa Powell) and a mere mortal
That concludes this month’s review of some great research material. Until next time!
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