This page is an evergrowing library of sports science and strength & conditioning infographics.
Sports Science Infographics
Acute to Chronic Workload Ratio
What is the Acute to Chronic Workload Ratio
The Acute to Chronic Workload Ratio (ACWR) describes the ratio between the short term workload (generally 7 days), and long-term workload (generally 28 days).
The optimal use of the ACWR can help practitioners to enhance performance by improving athlete freshness or readiness and reducing injury risk. But also by giving an idea, whether the athletes are training enough, or not.
Models of ACWR
There are two models which can be used to determine the ACWR.
The first option is the rolling average, this simply creates the ratio by using the average workload over 7 days for the acute workload and the average workload over 28 days for the chronic workload.
For example, if the average workload over 7 days was 2000 units, and the average over 28 days was 1800 units, the calculation would be:
The second option for calculation is the exponentially weighted rolling average, this model determines older workloads as less important by using a weighting system. This model appreciates the dissipating influence of training workloads which were accumulated further away from the acute workload.
Using the ACWR data
<0.80 – This is considered under training, and has a higher relative injury risk.
0.8-1.3 – This is considered optimal workload, whereby relative injury risk is at its lowest.
<1.5 – This is considered the ‘danger zone’ where there is a high relative injury risk.
Spikes in training load greater than 10% appear to increase relative injury risk, therefore it is recommended to keep the weekly variation in training load under 10%.
The ACWR is a simple but crucial part of the training program for any athlete, using the data appropriately can help coaches optimize performance, and reduce the risk of injury.
This Sports Science Infographic is a summary of the article Acute: Chronic Workload Ratio from Science For Sport.
Plyometric Training Infographics
What is Plyometrics
Plyometrics training involves jumps, hops, bounds, and skips to use the stretch-shortening cycle (SSC) to produce large forces, generally with the goal of improving maximal power output.
The Stretch-shortening Cycle (SSC)
The SSC involves the following muscle actions: an eccentric phase, followed by an amortization (or translational) phase, and a concentric phase.
The SSC in plyometric exercises may be considered ‘short or ‘long’, this depends on the time spent in the amortization phase. Amortisation phases in short SSC plyometrics are <0.25ms, whereas amortization phases in long SSC plyometrics are considered as being <0.251ms.
There are many potential mechanisms which underpin plyometric training, these include but are not limited to the storage and usage of elastic energy and motor coordination.
Plyometric training is not suitable for all athletes, these exercises often combine highly technical skills, with large forces. Athletes should, therefore, be suitably trained before starting plyometric training.
Plyometric training has been shown to improve many aspects of performance, for example, strength, power, speed, and jumping.
Plyometric training is used to develop power, speed, and strength due to the adaptations of the muscle-tendon system and nervous system.
This infographic is a summary of the article Plyometric Training from Science for Sports.
This strength & conditioning infographics outlines the stretch-shortening cycle (SSC), including what the SSC is, the underlying mechanisms, the difference between a slow SSC vs fast SSC, the energy storage and the neurophysiological model.
What is the SSC
The stretch-shortening cycle involves three stages. Firstly the muscle undergoes an eccentric action, secondly, the muscle undergoes a transition (also called amortization) phase, this is the time between stage one and three. Stage three is the concentric phase. An example of this would be stepping off a box, and landing, then immediately jumping to a second box.
Provided that the eccentric and amortization phases are fast, the corresponding concentric phase can utilize stored elastic energy like a spring. The faster the first two phases, the more elastic energy can be produced.
It is worth noting, that it is debated, whether the muscles involved, actually work eccentrically and concentrically, or whether the muscles contract isometrically and the recoil is provided by the stretching and shortening of the tendon.
Fast vs slow SSC
The speed of the SSC depends on the action occurring, with actions below 250ms described as fast stretch-shortening cycle, and actions over 250ms are described as a slow stretch-shortening cycle. Synonyms are a short stretch-shortening cycle for the fast SSC and long stretch-shortening cycle for the slow SSC.
Mechanisms of the SSC
The mechanisms which underpin this effect are still not fully understood, however, a range of hypotheses have been suggested, with varying levels of evidence to support them.
Mechanisms include elastic energy storage in the muscle-tendon unit (MTU) during the eccentric phase and amortization phase, that allows an additional propulsive force during the concentric phase. The engagement of the muscle spindles during the eccentric phase, which leads to an augmented firing frequency and stronger recruitment of muscle fibers and the active state, which refers to the time available for the cross-bridging formation, which improves the concentric force output.
Stretch-Shortening Cycle Conclusion
In conclusion, understanding the SSC is an essential component of plyometric training. The SSC is a spring-like mechanism, that can enhance athletic performance in explosive sports, as well as endurance based sports. Well trained athletes often have highly developed SSC capacities, it is therefore worthy of attention in any training program.
This sports science infographic is taken from the article Stretch-shortening Cycle (SSC) from Science For Sports.
Strength Training Infographics
Chain Resistance Training
Chain resistance training involves adding heavy chains to your lift, generally at the end of the bar. It is a form a variable resistance training which increases the weight added as the chain moves off of the ground.
Benefits of Chain Resistance Training
Generally speaking, this ensures that a lift is heavier in the easier portion(s) of the movement. Chains have a linear mass displacement, and therefore for each link added, there is an equal amount of weight added to the bar.
An example of Chain Resistance Training
Take the example of a bench press, as the bar is moved further from the ground, more links of the chain come off of the ground, adding more weight to the bar. In the bench press, generally, people are strongest at the top of the movement, as the bench press has an ascending strength curve the use of chains here ensures that the top range of movement receives a larger stimulus than a traditional bench press.
The practical application of using chains
Understanding how chains can influence the kinetics of your movement is important, chains have been shown to increase both peak force and impulse, but you must also consider that they have been shown to reduce peak and average barbell velocity, peak and average power, and peak rate of force development.
Using chains with weight above 15% of your 1RM has been shown to elicit changes similar to those described above. Despite these results, there is still a lot we need to learn about chain resistance training, if this taster has got you interested, this Sports Science infographic is a summary of the article Chain-Resistance Training from Science For Sports.