I’m a science nerd. It was my best subject through school and this thirst for science and love for sport is what took me down the road of physical preparation as a career. Alongside coaching, I like to write. I synthesize the latest research for coaches in the trenches on my websites Sweet Science of Fighting and Lift Big Eat Big, as well as contribute research updates to Science for Sport. Being exposed to the latest research each month I get to see where the trends are heading and what might be emerging in the future. As 2021 comes to a close, below are a few of my thoughts on current trends in sports science research.
Blood flow restriction during warm-ups
Blood flow restriction (BFR) training isn’t a new concept, but it has gained increased interest recently in a variety of areas from strength to rehabilitation. One new use has also been gaining traction recently in research: Using pressure cuffs to restrict blood flow during a warm-up. Specifically, two papers from 2017 and 2021 are very interesting. The idea is by restricting blood flow, you increase physiological stress without the increase in warm-up intensity. This particular 2021 study took twelve sprinters and had them perform 5 x 2 minutes of running at 50% heart rate reserve with 1 min between sets either with BFR cuffs or without.
While heart rate, RPE, and blood lactate were higher in the BFR cuff condition, no difference was seen in 60 m sprint performance between the warm-up conditions. However, the BFR condition increased knee flexor isokinetic strength at slow and fast speeds but not knee extensor strength increasing the Hamstrings:Quadriceps ratio.
What does all that mean? While BFR didn’t directly enhance performance, it suggests that ischemic pre-conditioning could potentially be used for those susceptible to hamstring injuries or returning from a hamstring injury before speed training.
The 2017 paper, while not dealing in warm-ups, really peaked my investigative mind. In recreational students, 6 x 100-meter runs at 60-70% maximum velocity twice per week for 6 weeks with BFR cuffs improved 100-meter sprint time greater than the group that didn’t use BFR cuffs. mFurther, the BFR group saw hypertrophy of the rectus femoris and improved rate of force development. Again, this is another potential application for the return to play athlete.
Whether these results translate to the professional athlete is yet to be seen. But the fact that we can induce greater physiological strain at low intensities (just like altitude training or heat acclimation), without expensive equipment has some interesting applications not only for injured athletes, but potentially for athletes training in cold weather or that are deloading.
What we don’t know is how much is too much. What kind of warm up with the BFR cuffs induces too much blood lactate and fatigue? How long is too long to wear the cuffs? At what point does a warm-up negatively effect the following activity? There is plenty more to answer within this topic and I look forward to more research on the topic.
Timelines for detraining and retraining
Over the last two years we’ve seen first hand how important it is to understand detraining and retraining. Extended lockdowns and training breaks have meant that research and application of detraining and retraining more important than ever. For so long we’ve referenced Issurin’s Training Residuals as the holy grail of how long we retain physical qualities. But Martin and I are working on a piece about how that table falls short and how little real research data is behind that. Detraining and retraining are hardly as formulaic as most people think and it is time for research to give this area the focus it deserves. To give a brief overview, a multitude of factors influence how long physical qualities are retained with detraining or reduced training:
- The type of training performed before detraining.
- The volume and intensity of training performed.
- If any exercise is performed within the detraining period.
- How strong, fit, or experienced the athlete is.
Generally, it seems the more well trained the athlete, the faster the loss in any physical quality (endurance, strength, speed). Further, the volume and type of training done leading into the detraining period heavily influences how qualities are retained where performing high volumes of heavy strength training may acutely depress force capabilities allowing supercompensation to occur during a detraining period. Most startling is how quickly aerobic qualities are lost when the training residuals table illustrates aerobic endurance is retained for approximately 30 days. In just 2 weeks (and in some cases, 2 days) aerobic qualities start to decline in well-trained endurance athletes. More research is needed investigating changes in anaerobic glycolytic performance and how it is affected by periods of no training.
Regarding retraining, there is limited research in this area and is something that would fill a gap within the literature. Anecdotally, many physical qualities return quickly after short periods of detraining.
Momentum vs. max velocity vs. change of direction
I love the research being published in collision sports looking at momentum rather than just maximum velocity. Collision sports require more than just speed. It requires the ability to break the defensive line or contact situations. The more momentum an athlete can create into a contact situation, the harder it will be for the defender to stop the athlete describing momentum as way to quantify a player’s resistance to stopping.
Taken a step further, momentum is related to dominant carry ability in rugby while going into contact with low momentum increases the risk of injury. So not only does increasing momentum enhance performance, it doubles as a way to reduce the risk of injury in contact.
While overloading resisted sprinting at optimal power load is popular within the research, very little has been done on overloading momentum. One study determined that a 10-meter sled sprint with 35-76% of body mass as external load was the optimum load to maximize momentum. Since sled sprint momentum was highly correlated with unresisted sprint momentum, it suggests this overload could translate to unresisted sprinting.
Momentum can also be applied to the change of direction deficit (CODD). Based on this paper, this is how you could profile athletes from a 5-0-5 test, linear sprint momentum, and body mass data:
- Higher momentum, faster 505-time, greater CODD = more technical COD training.
- Higher momentum, faster 505-time, lower CODD = balanced training programme.
- Higher momentum, slower 505-time, greater CODD = likely too heavy or isn’t strong enough relative to body mass.
- Higher momentum, slower 505-time, lower CODD = needs speed as an emphasis.
- Lower momentum, slower 505-time, lower CODD = prioritize strength and speed training.
- Lower momentum, slower 505-time, greater CODD = overall athletic development needed.
- Lower momentum, faster 505-time lower CODD = prioritize gaining body mass (if needed for sport).
- Lower momentum, faster 505-time, greater CODD = likely needs to prioritize strength training (especially eccentric strength).
This may be more applicable to sports that have many 180° CODs such as cricket but can still be used within team and individual sports. My physics might be a a bit rusty, but it seems that if we are maximizing momentum during a resisted sprint, we are also maximizing impulse due to the impulse momentum relationship. Perhaps this is a better way of maximizing horizontal force development for speed compared to slow, heavy sled drags.
Athlete autonomy to enhance performance
For many of the great coaches, athlete autonomy is the goal. You could argue that many of the most dominant sports teams around the world are largely athlete led or the athletes are given a great deal of responsibility around the team’s culture and playing style.
But athlete autonomy extends beyond the on-field sport coaches. The athletic performance department wants to guide their athletes to figure out for themselves their own warm-up routines that they love, and be able to get training started if coaches are still in a meeting.
We can take this a step further and use the idea of self-selection. For example, when competitive kickboxers choose their own punching combinations, they see enhanced punching velocity by 6-11% and impact forces by 5-10%.
The idea of self-selection has been taken into the weight room in both a maximal strength testing capacity and post activation potentiation. The first study conducted two experiments. Firstly, subjects that self-selected which hand they used first during a handgrip test showed greater grip strength than those who were told which hand to use.
Secondly, the subjects that self-selected load increases and reductions during a 1RM back squat test increased their squat to a greater extent than the group who mirrored their percentage load increases.
More recently, Iacono and colleagues published a very robust study with professional basketball players with self-selections effect on post activation potentiation. Players either completed each of these protocols using the jump squat:
- PAP1: 3 x 6 @ optimal power load
- PAP2: Self-selecting repetitions based on how they felt to minimize fatigue and maximize subsequent exercise performance.
- PAP3: researchers told the players how many reps to perform each set which was matched exactly to the number of total reps performed during each set when they self-selected, however, subjects did not know this.
At 4 and 8 minutes after the jump squat, athletes performed a squat jump on a force plate. PAP2 led to greater jump height, GRF, and impulse compared to the other conditions.
The idea of self-selection is a growing area of research that is highly applicable to our coaching practises. As the idea of athlete or player led teams grows in the spotlight, this is potentially a way to provide athlete autonomy with experienced players.
This is just a snapshot of some of the research I’ve had the pleasure of reviewing over the past year and earlier. There are still plenty of questions to answer so if you are embarking on a new research project, I hope these spur some thought into some new research topics.