Freelap Friday Five with Chris Bishop
Chris Bishop is a Senior Lecturer in Strength and Conditioning at Middlesex University, London, U.K., where he is the Program Leader for the MSc in Strength and Conditioning. He is also the Strength and Conditioning Coordinator for the newly formed NFL Academy in London, which aims to develop the next generation of American football players outside of the U.S. Bishop also serves as the current Chair of the Board of Directors for the UK Strength and Conditioning Association.
Freelap USA: You have done research on the barbell hip thrust and find it doesn’t have a big impact on performance. The research you have done on horizontal and vertical forces is also very well-designed. Why do you think coaches use the exercise, even knowing the research is mixed? What do you think about incorporating the exercise at the moment?
Chris Bishop: For me, the hip thrust is just another exercise that practitioners can call upon in their programming, if they deem it beneficial for their athletes. In the right circumstances, I’m sure it can be useful, and assuming technique isn’t compromised, it does seem to allow heavy loading for the glute complex, which probably has some benefits for those athletes who need greater strength in their posterior chain muscles1. However, I wouldn’t really classify it as a compound lift, owing to the predominantly isolated movement at the hip joint.
Equally, when you consider how strength and conditioning coaches often judge “performance” in team sport athletes (which they often do via jump, sprint, and change of direction ability), it is a little surprising to me that any single isolated exercise would have a substantial and beneficial effect on such measures of performance. As is often the case in research, it seems some studies have shown the hip thrust to be a viable option for enhancing athletic performance2,3, while others have not4,5.
However, I haven’t seen any research that aims to quantify both vertical and horizontal forces during the hip thrust, something which might help coaches understand how forces are applied. Given the conflicting opinions on the orientation of the hip thrust6,7, this seems like a potentially interesting line of investigation for those who are unclear as to its efficacy.
Freelap USA: Specificity is a very controversial subject with coaches, as there are so many different views on what transfers ideally. For young coaches needing a balanced view, what is your perspective on the balance between general overload and programming that could give more direct returns, such as weighted sleds? Any words of wisdom for team coaches who may not have the sports science background?
Chris Bishop: I’m sure this is the type of question that technical coaches often want the answers to, and there is no doubt that some coaches perceive specificity as best achieved by exercises that mimic the sporting action. In reality (and I believe this is almost always the case in S&C), the answer is probably “it depends.” If athletes don’t have a particularly high training age in the weight room, it’s probably fair to say that you can do almost any well-planned and well-coached training with them and they will make improvements. This is supported in the literature, which shows that simply getting stronger can translate to improvements in jump and sprint ability, particularly in weaker athletes8,9.If athletes don’t have a particularly high training age in the weight room, you can probably do almost any well-planned and well-coached training with them and they will improve. Click To Tweet
Similarly, when athletes show greater strength levels as a consequence of consistent training over time, there is potentially a stronger case to consider more specific modes of training (e.g., using weighted sleds for the purpose of improving acceleration)10. However, noting that many team sport athletes (regardless of training experience) need to develop multiple physical qualities, a concurrent or mixed-methods approach will likely be the most suitable strategy11.
The key question then becomes when to apply these different modes of training. In truth, what works for one athlete may not work for another, so coaches should aim to determine which exercises are most effective for their athletes. However, prioritizing compound strength, weightlifting, and plyometric exercises likely serves as a decent start point for less-experienced or weaker athletes.
Freelap USA: Isometric testing is important for many coaches who want to program strength after testing jumps. With your unilateral dynamic strength index, can you share some example workouts that could showcase how to apply the testing metric? There are many excellent articles that explain the test, but not the application. You have a lot of practical experience, so perhaps you can provide good examples of application.
Chris Bishop: Before discussing programming implications, the first thing to acknowledge regarding the dynamic strength index (DSI)—regardless of whether it is used bilaterally or unilaterally—is that it is a ratio. This means it is made up of two constituent parts (e.g., left and right or dominant and non-dominant), each of which has associated error attached to it. However, when you create a ratio such as the DSI, it has to absorb both sources of error, which practitioners should be mindful of when considering the reliability and usability of the data.
Existing research on the bilateral DSI has hypothesized that for athletes with scores between 0.6 and 0.8, coaches may wish to employ a concurrent (strength and power) training approach. For scores >0.8, coaches could consider focusing on strength training, and for scores <0.6, they should focus on ballistic training12–14. To the best of my knowledge, only one empirical study has investigated the unilateral DSI, using recreational rugby and soccer athletes15. When defining limbs as “left and right,” unilateral DSI values ranged from 0.52–0.59 across two test sessions. When defining limbs via dominance (dominant being defined as the stronger limb), values ranged from 0.53–0.57.
Although making inferences from a single study about thresholds is ill-advised, it seems highly unlikely that the same suggestions of <0.6, 0.6–0.8, and >0.8 would be applied to this ratio unilaterally. However, it seems reasonable to suggest that a training program that focuses on unilateral strength exercises (e.g., rear foot elevated split squats, split squats, step-ups, single leg squats—I know some of those suggestions aren’t strictly unilateral) would reduce the DSI value. Similarly, focusing on unilateral jump training (e.g., single leg hops, single leg countermovement, and drop jumps) would likely improve an athlete’s ability to use more of their peak force ballistically; thus, increasing the DSI score.
With all things considered, it feels prudent to suggest that more research is needed on the unilateral DSI before we can make any substantial claims about its usability. As always, I advise coaches to program for what their athletes need, not solely to improve a test score.
Freelap USA: Acceleration and change of direction have a relationship that can be fuzzy without testing the qualities directly. Obviously, you are familiar with the work of Tom Dos’Santos, so could you expand on how to test athletes beyond the conventional 5–10–5? You did a great job with the Spider test; perhaps something new can be done to help coaches see backpedaling or similar? Most acceleration patterns seem to be forward, when going backward could be a valuable or maybe illusionary quality. Any ideas outside of the lateral tests for change of direction and common linear speed evaluations?
Chris Bishop: One area that has been getting a lot of attention in recent years is the change of direction deficit, CODD16. Given that linear and change of direction speed tests often appear in fitness testing batteries for team sport athletes, it is no surprise that the CODD’s popularity has increased in both the research and applied settings. To get the CODD, you subtract the total time taken to perform a linear sprint test from the total time taken to complete a change of direction speed test of equivalent distance (e.g., 505 time = 2.5 seconds; 10-meter time = 1.8 seconds; CODD = 0.7 seconds).
It has been suggested that many change of direction speed tests are biased toward the linear sprint component of the test16,17; thus, the CODD may provide a more realistic picture of an athlete’s ability to change direction. However, similar to the DSI, the CODD is made up of two constituent parts, which means that changes in CODD scores should be interpreted in conjunction with individual linear speed and change of direction speed data.
To understand this further, the aforementioned example provided a CODD of 0.7 seconds, but if an athlete then showed improvements after a training intervention and completed the 505 test in 2.3 seconds (but no change in 10-meter time), their CODD score would now be 0.5 seconds. With no changes in linear speed evident, the coach can assume (based off the data this provides) that the athlete has gotten better at changing direction. In contrast, if the athlete also showed an improvement of 0.2 seconds in 10-meter time (as well as a 0.2-second improvement in 505 time), the CODD remains at 0.7 seconds, but in this scenario, both linear and change of direction speed tests improved. Thus, coaches should be cautious about making any decisions purely based off ratio data and are always encouraged to look at the individual components.Coaches should be cautious about making any decisions based purely on ratio data and should look at the individual components, says @ChrisBishop_UK. Click To Tweet
Given the inherent issues that can accompany ratios, a more in-depth look at change of direction strategy also seems like an appropriate suggestion, and it would provide data beyond measures of time. As such, entry and exit velocity during change of direction tasks could be a viable option for helping coaches understand how effectively athletes are braking and reapplying force. Interested readers should refer to the works of Dr. Sophia Nimphius, Tom Dos’Santos, and Richard Clarke for a more detailed understanding of the topic.
Freelap USA: One topic that you have great expertise in is asymmetry, where you are able to do a lot of testing and programming from the data. If you were to help the NFL screen players for the Combine, what setup would you use that would be efficient and effective? Ideally, you have as many resources as needed with equipment and personnel, and you have five days to implement the program along with the conventional sprint and jump tests. Any ideas?
Chris Bishop: Tough question… I guess I would draw upon many of the investigations we have conducted and say that I think the single leg drop jump (SLDJ) could be a viable option in this sport. We have found, on numerous occasions, that asymmetries in jump height (from the SLDJ test) are significantly associated with reduced change of direction speed (and sometimes linear speed) performance in team sport athletes18–20 (in addition to references, there is more work currently under review for this). We haven’t done any mechanistic investigations on this, so it’s hard to provide a definitive conclusion. However, performing drop jumps requires a very specific transition from braking to then reapplying propulsive force, as athletes look to minimize contact times and maximize jump height.
There is a likeness to this notion when you perform change of direction tasks such as the 505 test (i.e., athletes need to brake in preparation for the turn before reaccelerating and applying propulsive forces again). Thus, although inherently different tasks, it does seem plausible that if you have one side that performs distinctly worse during a SLDJ, this might be associated with how well you perform a change of direction speed task. In addition, this might detrimentally affect the use of the stretch-shortening cycle during sprinting/change of direction speed tasks, serving as another possible reason why associations exist between larger drop jump asymmetries and such movement patterns18–20.
Given the importance of linear and change of direction speed for some positions in American football, this could be a viable option for the assessment of side-to-side imbalances. This might sound like a rather simple suggestion, given that your question outlined there were no restrictions on resources. However, some of our previous work has also quantified multiple metrics during unilateral jump tests, via the use of force plates. This has provided a more in-depth analysis of asymmetries pertaining to metrics such as propulsive and braking impulse and force, rather than outcome measures alone.
Yet, in my experience, the most consistent and reliable asymmetry metrics are still the outcome measures, such as jump height. As ironic as that might sound, the advantage of this is that you don’t need a force plate to measure jump height asymmetry from a single leg countermovement or drop jump test. I should reiterate, though, that I advise practitioners not to make decisions based off ratio data alone.In my experience, the most consistent and reliable asymmetry metrics are still the outcome measures, such as jump height, says @ChrisBishop_UK. Click To Tweet
Some of our additional work has shown that the direction of asymmetry (the side which consistently shows the larger score) can vary between tasks21,22 and test sessions23. Thus, it is key that coaches understand whether an asymmetry is consistent before considering how to act on that data. For more information on how to calculate the consistency of asymmetry between test sessions, please see this YouTube video link.
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1. Contreras et al. “A comparison of gluteus maximum, biceps femoris, and vastus lateralis electromyography amplitude for the barbell, band, and American hip thrust variations.” Journal of Applied Biomechanics. 2016; 32:254–260.
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3. Dello Iacono et al. “Loaded hip thrust-based PAP protocol effects on acceleration and sprint performance of handball players.” Journal of Sports Sciences. 2018; 36:1269–1276.
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18. Bishop et al. “Drop jump asymmetry is associated with reduced sprint and change-of-direction speed performance in adult female soccer players.” Sports. 2019; published ahead of print.
19. Bishop et al. “Effects of inter-limb asymmetries on acceleration and change of direction speed: A between-sport comparison of professional soccer and cricket athletes.” Journal of Strength and Conditioning Research. 2019; published ahead of print.
20. Maloney et al. “Do stiffness and asymmetries predict change of direction performance?” Journal of Sports Sciences. 2017; 35:547–556.
21. Bishop et al. “Interlimb asymmetries: The need for an individual approach to data analysis.” Journal of Strength and Conditioning Research. 2018; published ahead of print.
22. Bishop et al. “Comparing the magnitude and direction of asymmetry during the squat, countermovement and drop jump tests in elite female soccer players.” Journal of Sports Sciences. 2019; published ahead of print.
23. Bishop et al. “Using unilateral strength, power and reactive strength tests to detect the magnitude and direction of asymmetry: A test-retest design.” Sports. 2019; 7:1–14.