Dr. Aaron Uthoff is a Research Fellow at the Sports Research Institute of New Zealand and Auckland University of Technology, where he lectures on principles and applications of strength and conditioning. He is also a strength and conditioning consultant who specializes in training sprint athletes. Aaron received an MSc(d) in Performance Psychology from the University of Edinburgh and a PhD in Sport and Exercise Science from Auckland University of Technology, and he has been a Certified Strength and Conditioning Specialist through the NSCA since 2014.
Freelap USA: Backward running research is not as extensive as it needs to be. Can you explain what you have learned about the value of running backward and how we can use this information in training?
Aaron Uthoff: One of the biggest takeaways from diving into backward running (BR) research was the importance of running technique. The way that coaches cue BR technique will affect the outcomes. When you tell an athlete to run backward as fast as they can, they tend to keep the leg as a long lever and almost fall backward, as opposed to thinking about having high heel recovery and being tall (not dissimilar to common cues used by some speed coaches).
The high heel recovery, I believe, helps transfer to forward sprinting and vertical jumping because it means BR can be used as a dynamic knee extensor and hip flexor strengthening method. One thing to keep in mind with the high heel recovery, though, is that bicep femoris activity increases when hip extension and knee flexion occur simultaneously (see this fresh-off-the-presses article by Hegyi et al. This can lead to some serious DOMS, or even acute hamstring strains, if BR is not progressively overloaded.
Coaches usually consider which tissues need to be preferentially targeted during specific training phases. Since the leg acts as a pendulum during the stance phase of BR, as opposed to a spring during FR, less elastic energy is utilized, and the musculotendinous unit relies more heavily on the contractile properties of the motor unit to produce force. This, along with wider step width, leads to greater energetic cost during BR compared to relative efforts during forward running (e.g., 50%, 75%, or maximal effort). Therefore, BR may be used as a specific method to train the contractile tissues and as a conditioning tool when coaches want to add variety and reduce total running volume in their athletes’ programs.
Coaches may use backward running as a specific method to train the contractile tissues and as a conditioning tool to add variety and reduce total running volume in their athlete’s programs. Share on XAnother thing I found interesting is that BR is characterized by lower horizontal ground reaction forces compared to FR. This means that BR places less mechanical strain on the lower limbs in the anteroposterior direction. Therefore, BR may be a tool that coaches and clinicians can use with athletes in rehabilitation and return to performance settings.
Freelap USA: The use of shank and thigh wearable resistance is growing again in the international sports scene. Can you give some recommendations to those who are in team sports such as American football so they can periodize it or use it in return to play?
Aaron Uthoff: Many coaches got turned off the idea of adding loads while performing sport-specific movements because the antiquated technology was cumbersome and altered normal mechanics. However, recent advancements in garment technology have enabled loads to be placed in a multitude of ways across different regions of the body without clunking around and disturbing normal movement patterns.
Normally, when we think about increasing load, we go straight to adding more weight. The unique thing about modern wearable resistance training is that overload can be applied in two primary ways: 1) simply add more weight or 2) move the same weight from a proximal location to a more distal location (think thigh loading, where you could start with the load close to the hip and then move the same load down to above the knee). We all know how the first method provides overload; however, the second method works because it increases rotational inertia. (For a deeper dive, check out Professor John Cronin’s article.)
What I particularly like about shank loading (for wearable resistance) is that it provides dynamic eccentric strengthening for the hamstrings, says @amuthoff. Share on XAs wearable resistance loads the musculature across the joints proximal to where it is located, shank loading provides the most bang for your buck since it will train the muscles around the knee and the hip. What I particularly like about shank loading is that it provides dynamic eccentric strengthening for the hamstrings, as they are required to decelerate the additional load during the mid-to-late swing phase. This has implications for both performance and return to play, depending on the athlete and phase they are in.
When it comes to loading for performance, it is always good to start light and proximal with loads roughly equivalent to 0.5% of the athlete’s body mass placed neutrally (i.e., evenly distributed on the anterior and posterior lower leg) on each limb. Progression would follow a normal linear periodization strategy where the load would be moved halfway down the shank in week 2, and then fully distally placed in week 3. The load would then be increased by 0.25% (i.e., it is now 0.75% of the athlete’s body mass) and returned to the most proximal location.
This could be repeated up to 1% body mass, allowing for a nine-week progressively overloaded training phase. Remember, there will be additional stress placed on the musculature, so it is recommended that this be introduced in the off-season after a general preparatory period.
For those interested in utilizing wearable resistance as a return to play strategy, the loading progression could look very similar to the one used for performance enhancement. However, as any return to play protocol will slowly build up running velocity, wearable resistance should be implemented at the lowest velocity and be progressed accordingly, at the discretion of the coach, physio, or clinician.
Freelap USA: The Pro Agility is a test that needs to have more insight besides time or splits. Can you help the reader with some nuggets of wisdom for a few more ways to extract more information outside of adding more timing gates?
Aaron Uthoff: It’s hard to believe that total time in the Pro Agility test is still the primary measure of interest, since a large component of the test involves linear acceleration, and it does not actually capture change of direction ability, let alone agility, as the name suggests.
The problem with the current approach is that an athlete can mask poor change of direction ability if they are really good at accelerating in a straight line. We’ve found that simply adding two additional timing gates 1 meter or 2.28 meters to either side of the change of direction line can provide more diagnostic information around different performance abilities, such as acceleration from a static start versus a flying start and change of direction ability from high- and low-entry velocities. However, while this allows us to home in on the different sections, timing gates alone don’t enable us to isolate the deceleration, exact change of direction, and reacceleration in and out of that 1-meter or 2.28-meter change of direction zone.
The problem with the Pro Agility test’s current approach is that an athlete can mask poor change of direction ability if they are really good at accelerating in a straight line, says @amuthoff. Share on XWe’ve been playing around with using radar and laser (stay tuned for the journal article) to identify splits of the Pro Agility to truly identify acceleration, deceleration, change of direction, and reacceleration performance. This is important because how well an athlete performs in a given phase of the test will help coaches determine the type of training the athlete requires. For example, if an athlete performs well over the first acceleration phase, but not the deceleration phases, then they likely have good concentric strength and need to work on their eccentric strength. Similarly, if an athlete gets stuck in the change of direction, it is likely that they lack eccentric and isometric strength, therefore indicating to the coach what sort of programming the next training phase should focus on.
Timing gates and radar/laser are helpful. But coaches can get most of this information from simply capturing video of an athlete performing the test. If they set up a camera so that it captures the change of direction and 2.28 meters before and after it, they can pop the video into free software, like Kinovea, and compare the performance between the different phases—essentially calculating entry and exit ratios. The upside of getting video is that coaches also have a qualitative tool to assess an athlete’s change of direction technique.
Freelap USA: Rotation and upper-body motions are often important but difficult to test reliably. Based on your experience, what can the seated chest throw with a medicine ball provide to practitioners who don’t have access to high-tech instrumentation?
Aaron Uthoff: It is important that coaches consider the reliability (i.e., repeatability) of a test prior to using it as a benchmark for their athletes. Tests that have high reliability between trials or testing occasions should be used for long-term athlete monitoring because any changes in performance can be linked to the effectiveness of training, and therefore coaches can be confident that these results are true and not consequences of technological or biological variation.
Since kinematics, such as peak displacement and velocity, have been found to be reliable for tests such as a cable put and seated cable rotation test, the very practical test of a seated medicine ball throw for distance would likely also be reliable, albeit with ample familiarization of at least one or two sessions prior to collecting data that will be used for monitoring purposes. This would be a great test on multiple fronts:
- Coaches can compare dominant and non-dominant side performance to understand whether asymmetries affect performance.
- Coaches can quickly get load-displacement/velocity relationships by testing using medicine balls of different weights.
- The test is not overly taxing, so it may be used within a normal training session, and throughout a competitive season, without causing undue fatigue.
One thing I’d recommend is for coaches to ensure that testing is standardized. They might do this by making sure that athletes use the same type and size of medicine ball (e.g., slam, wall, or dead ball) for each test, as the compliance/malleability of the ball means it will leave the hand differently and that affects performance. Additionally, it is important that coaches make sure athletes throw from the same height for each testing occasion and try to minimize the contribution from the lower limbs as much as possible. They can achieve this by having an athlete sit on an immoveable bench or on the ground and strapping their thighs down so they can’t utilize axial rotation of the hips.
Freelap USA: Arm action is a gray area with many researchers, and you have experimented with various forms of interventions for developing good arm mechanics. Is there anything from the last few years you feel is helpful after releasing your journal article?
Aaron Uthoff: Arms obviously play a critical role in sprinting, regardless of whether you sit in the camp that believes they merely maintain balance for the contralateral leg or hold the belief that they aid propulsion in the intended direction (i.e., horizontal during acceleration or vertical during maximal velocity). I don’t think these two are mutually exclusive. Rather, I believe that arm drive acts to enhance the back engine by increasing axial dissociation between the shoulders and the hips, countering the body’s rotation initiated by the pelvis, subsequently increasing both horizontal and vertical ground reaction forces, leading to better running performance.
One of the primary reasons for this idea is that we have found when an athlete sprints with 1% body mass of wearable resistance on each forearm, propulsive impulse increases over the first four steps and vertical impulse is greater from the fifth step onward. These increases in phase-specific forces coincide with longer step lengths.
If an athlete can maintain the same arm speed—and therefore step frequency—but they pump their arms more powerfully, this will lead to greater ground reaction forces and longer step lengths. Share on XIf an athlete simply pumps their arms faster, this does not mean they will necessarily run faster. Rather, if an athlete can maintain the same arm speed—and therefore step frequency—but they pump their arms more powerfully, this will lead to greater ground reaction forces and longer step lengths.
Effectively, since speed is the product of step length and step frequency, this would improve running speed. However, as any speed coach will know, athletes need to do this in as relaxed a manner as possible, so as not to lead to tightness in the shoulders. Therefore, coaches need to be mindful to walk the fine line of cueing the athlete to be aggressive with their arm action but find the intermuscular coordination to be able to switch on and off the right muscles at the right time, so they are not running around like Quasimodo.
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