How Ground Contact Times Help With Exercise Selection in Sprint Training

How Ground Contact Times Help With Exercise Selection in Sprint Training

To make your training program most effective, it helps to know what aspect of performance you are developing with the exercises you select. In today’s video, we will be discussing how you can use ground contact times in certain exercises to decide which exercises to use for developing specific parts of the sprint. First we will cover ground contact times in sprinting, then we will discuss how tempo endurance training, resisted sprinting, and jump training are relevant to sprinting, within the lens of ground contact times. We’ll finish by talking about some progressions and ideas that may be helpful for you in planning your own training program.

Ground Contact Times & Relatedness To Sprinting

In deciding how relatable an exercise is to sprinting, we can look at things like ground contact times, ranges of motion, body positioning, force vectors, and probably a lot of other qualities. Ground contact times are easy to quantify, so for the sake of this video we will be looking that, but understand there are many other factors that you can and should consider.

When deciding where a certain jump exercise, depth jump height, or sled load, ground contact times can help us get some idea of what part of the sprint a given exercise might be most relevant to. It's worth noting that ground contact times may vary quite a bit depending on fatigue levels and whether minor injuries are present, but we can still use ground contact times as one representation of how specific or relatable an exercise is to sprinting.

Ground Contact Times In Sprinting

Taking a look at my own sprints, we can see ground contact times that are approximately as follows:

  • Step 0 - 0.35 - 0.40 (Block clearance)
  • Step 1 - 0.20
  • Step 2 - 0.13
  • Step 3 - 0.12
  • Step 4 - 0.12
  • Maximal Velocity - 0.08 - 0.10

Based on these numbers, we can start to parse out what ground contact time durations on exercises might be relevant to early acceleration, mid acceleration, or late acceleration and maximal velocity sprinting. Exercises with ground contact times which range from 0.3 to 0.4 seconds might be more relevant to block clearance or step zero, 0.2 to 0.3 being relevant to the first 10 meters of the sprint, and ground contact times below 0.2 being more related to later acceleration and maximal velocity.

Ground Contact Times In Tempo Endurance

When looking at my own extensive tempo running such as 6x150m performed at around 60-70% effort, I’ve found that my ground contact times range from 0.11 to 0.13, which is essentially the same times seen in early to mid acceleration. Given that the posture of tempo running is akin to maximal velocity, and the ground contact times are only a few milliseconds longer, it would be reasonable to assume that tempo endurance running might have the potential to play a role in improving maximal effort sprinting.

While the intensity of extensive tempo is far different from that of maximal effort sprinting, some of the component parts of tempo running such as ground contact times and posture are quite similar to faster sprinting. 

Because of the higher running volumes and longer distances used in extensive tempo, this lower intensity variation of sprinting gives the athlete many opportunities to perfect their ground contact mechanics, to manage their posture, and to properly recover the leg through the air. Also, since the overall intensities are lower than sprinting, the injury risk of extensive tempo is lower than maximal effort sprinting.

Considering these points, it makes sense that many of the most successful sprint programs in the world use a fair amount of tempo endurance training, and it is worth considering how you might benefit from using tempo in your own sprint training program.

Now let’s move on to resisted sprinting, and then we’ll discuss some jumping exercises.

Ground Contact Times In Resisted Sprinting

Resisted sprinting is a great training tool which allows us to overload force demands early in the sprint, practice getting into aggressive acceleration positions and postures, and to play around with how much emphasis we place on force versus stride frequency. 

The load used will dictate the effects of the work, with heavier loads possibly being more useful for early acceleration as compared to lighter loads. Obviously there is a point at which increasing load will begin to make the exercise less relevant to sprinting, but in general I think we get more out of resisted sprinting with increased loads, so long as we can still sprint or at least march with the load.

Research from Morin, Petrakos, Jimenez-Reyes, Brown, Samozino, and Cross suggests that 80% body mass sled loads were more effective at improving 10 and 20 meter acceleration times in soccer players as compared to unresisted sprinting, and research from Kawamori, Newton, Hori, and Nosaka shows that sled loads which caused a 30% increase in sprint times were effective at improving 5 meter and 10 meter acceleration times, whereas loads which caused a 10% increase in sprint times led to a smaller improvement at 10 meters, and no improvement at 5 meters. These studies help support the concept that heavier loads may lead to greater improvements in short sprints compared to lighter loads. Whether lighter loads help longer sprint distances compared to heavy loads is uncertain at this time, albeit something that might be logical to assume.

In my own training, 100lb sled pulls on turf show similar times as a 200lb sled for step 0, but I see significant differences in the later steps of the resisted sprint. For example, 200lb sled pulls did not go below 0.22 seconds of ground contact by step 5, whereas 100lb sled pulls showed ground contact times of 0.15 seconds by step 5.

Ground Contact Times - 100lb Sled on Turf

  • Step 0 - 0.62
  • Step 1 - 0.30
  • Step 2 - 0.20
  • Step 3 - 0.17
  • Step 4 - 0.16
  • Step 5 - 0.15
  • Step 6 - 0.14
  • Step 7 - 0.13

Ground Contact Times - 200lb Sled on Turf

  • Step 0 - 0.60
  • Step 1 - 0.25
  • Step 2 - 0.24
  • Step 3 - 0.23
  • Step 4 - 0.22
  • Step 5 - 0.22

With these numbers in mind, it seems to my pea sized brain that the 200lb sled pull on turf would be more relevant to the first couple steps of the sprint, whereas the 100lb sled pull on turf might be more relatable to mid-acceleration from 5 to 15 meters. 

For example if we see that an athlete struggles with the earlier steps of the sprint, they might benefit more from relatively heavier loads (such as the 200lb sled), seeing as the majority of the steps exhibit ground contact times similar to step 1 in unloaded sprinting, and the body positioning is more forward oriented than with lighter loads. This body positioning allows the athlete to work on stabbing back at the ground without opening up the knee, which is technique we tend to see in the first couple steps of the sprint.

Another athlete might clear the blocks well, but struggle between 5 and 20 meters. These athletes might be better off working with a lighter load, such as the 100lb sled, as the ground contact times and body positioning would be more similar to what is seen in mid-acceleration during unloaded sprinting. 

Jumping Exercises & Their Relatedness To Sprinting

Jump training and plyometrics are useful tools to have in your sprint training and speed development tool box. Being that jump training is a very broad category, encompassing everything from simple in-place hops to very intense depth jumps and bounding activities, it would help to have some buckets in which to place jump exercises as far as their relevance to different parts of the sprint. Let’s take a look at the ground contact times I’ve seen in various jumps, and see if there is anything we can take away from this as it relates to exercise selection.

From my own training data, the following jumps can be roughly categorized as follows:

Very Early Acceleration - 0.31 to 0.40 Ground Contact Times

  • 36" SJ - 0.40
  • 42” Walking CMJ - Straight Leg Landing - 0.40
  • 42” Reverse Depth Jump - 0.35
  • 48” Walking Countermovement Jump - 0.35
  • 36" Walking Countermovement Jump - 0.33

Early to Mid Acceleration - 0.20 to 0.30 Ground Contact Times

  • 6” Single Leg Horizontal Depth Jump - 0.30s
  • 24” Depth Jump to 36" Box - 0.28s
  • 12" Single Leg Depth Jump to 30” - 0.26s
  • 18" Depth Jump to 36" Box - 0.25s
  • 12” Depth Jump to 36” Box - 0.24s
  • Single Leg Cycle Bound - 0.22s
  • 6" Single Leg Depth Jump to 30” Box - 0.22s
  • 24” Depth Jump to 42" Box - 0.21s
  • 36” Reverse Depth Jump - 0.20s

Mid Acceleration to Maximal Velocity - 0.13 to 0.17s Ground Contact Times

  • 12” Depth Jump to 12” Box - 0.13 to 0.15s
  • Pogos Forward - 0.13 to 0.15s
  • In-Place Pogos - 0.13 to 0.17s

In all of these exercises, deeper knee bend typically equates to longer ground contact times, and this combination of knee bend and ground contact time helps shed some light on where in the sprint the exercise might be most relevant.

Early in the sprint, we contact the ground with deeper knee bend and we spend more time on the ground. As we accelerate and we rise to taller postures, ground contact times reduce and the leg becomes more straight during ground contact.

Just like we talked about with the sleds, we can look to the area of the sprint in which you need to improve, and target those qualities with exercises that are closer on the spectrum of relatability. 

For example, an athlete who struggles over the first couple steps of the sprint might be well suited to use squat jumps, progressing toward a squat jump that is immediately followed by a reverse depth jump. The squat jump itself has some relevance to block clearance or step zero because of the purely concentric nature, while adding the reverse depth jump adds relatability to step one as the athlete has to come back and apply force to the ground after the initial concentric jump. This exercise can be further progressed by adding more reverse depth jumps reps, or by modifying the box height.

In contrast, the athlete who struggles at top speed or fails to maintain high velocities after acceleration would likely benefit more from exercises like in-place pogo jumps, pogo jumps while moving forward, and possibly some very low height depth jumps that emphasize very brief ground contact times. Athletes who struggle with getting off of the ground quickly during sprinting can progress from moderate jump heights and medium duration ground contact times to lower jumps with shorter ground contact times, which will challenge them from a coordination standpoint.

Progressions Should Target Athlete Needs

In the past, I would often think about progression simply as either lifting more weights, jumping higher, and using higher drop heights in depth jumps, and other “more load” type of changes. Nowadays, I look at things a little bit differently.

For example, it is arguably easier to try to jump higher in a pogo hop at the expense of greater knee bend and longer ground contact times, compared to minimizing ground contact times. But how would it be helpful in improving maximal velocity sprinting when we do not have a lot of time available and we need only a small amount of vertical lift to get to the next stride?

Recently some research was put out by Jad Adrian Washif and Jian-Yee Kok which showed that jump height, flight time (which is a result of jump height) and reactive strength index (RSI) of 35cm (13.7in) depth jumps had significant correlations with faster sprint times, but did not see correlations with a 50cm (19.68in) depth jump. This might lend some credence to the idea that getting off of the ground quickly is more relevant to fast sprinting than jumps that might be more forceful, but take more time to get off of the ground due to greater amortization or joint yielding and knee bending.

This is not to say that higher depth jump heights are not useful for any sprinter out there, but considering the potential injury risk of high depth jumps, it makes sense to me that we can use low depth jumps with fast ground contact times in more athletes than we could higher depth jumps. Considering the lower depth jump was more correlated with fast sprinting (around 10.5s 100m dash versus 11.00s 100m dash), the combination of stronger correlations and lower injury risk seem to me like a good combination.

Once an athlete feels that a certain low depth jump height is no longer having an effect, they could progress the drop heights by small amounts while aiming to maintain similar ground contact times, RSI, and jump heights as they progress.

Conclusion

To wrap things up, when you are putting together a training program and you are trying to decide what exercises to include, some of your program can be built to target your weaker areas of the sprint.

If you find that you are struggling more with very early acceleration, consider incorporating some exercises which mimic the ground contact times and positions of that part of the race, such as by using heavier sled loads and jumps with longer ground contact times and higher force output demands.

If instead you accelerate well early in the sprint, but struggle with continuing to accelerate deeper into the sprint, you might be better off emphasizing shorter ground contact time duration exercises, such as using lighter loads on the sled, lower depth jump heights, or using exercises like pogo hops either in place or while moving forward over the ground.

Remember that this approach is not going to solve all of your exercise selection issues or cover every aspect of your training, but this approach can help guide you toward certain exercises and give you a better probability of seeing the adaptation that you feel you need.