Summary article: The importance of muscular strength in athletic performance (Suchomel, Nimphius & Stone, 2016)
It’s well established that muscular strength is a vital aspect of performance for many different sports. The ability to produce and absorb force (the exact definition presented in the paper is the ability to exert force on an external object or resistance) is a fundamental aspect of sporting performance, whether in relation to the environment (for example, for movement when sprinting), an object (for example, for manipulating an object or opponent, such as when hitting a baseball or making a rugby tackle), or a combination of the two. Therefore, an important part (but by no means the only part) of an athlete’s physical preparation and development should be made up of strength training to improve force output.
Through manipulation of force-time characteristics, an athlete can improve performance relative to their sport. By exerting more force in the same timeframe, higher levels of rate of force development (RFD) and higher levels of mechanical power can be exhibited (figure 1). RFD is defined as the rate of rise in force over the change in time, otherwise termed explosive strength, whilst mechanical power can be defined as the sum of joint powers that may represent the coordinated effort, normally of the lower body. Many sports require rapid movements whereby large amounts of force are produced in limited time constraints (~50 to 250ms). This highlights the importance of RFD as a longer period of time (~300ms) is usually required to reach peak force outputs, emphasising the need for greater levels of force to be produced in shorter timeframes. In short, a positive relationship exists between muscular strength (force output) and RFD, as stronger individuals are thought to be able to produce greater levels of RFD. Some of the most common movements in sport are jumping, sprinting and rapid changes of direction, with successful sporting performance correlating to performance in those movement tasks. Muscular strength can, therefore, have a significant influence on force-time characteristics, with enhancement transferring to the ability to perform movement skills.
Figure 1: Force-time graph. Although the two examples are across the same timeframe, the dark red line displays a greater RFD, producing higher levels of force across the same amount of time as the light red. This is typically a result of resistance training to improve muscular strength.
Injury risk reduction
An appropriately prescribed and progressive strength training program may also decrease overall occurrence of injuries, in both acute and chronic cases. It is thought that resistance training (improving strength levels) may reduce injuries due to increases in structural strength of ligaments, tendons, joint cartilage and connective tissue sheaths within muscles. Furthermore, bone mineral content may experience positive changes to reduce the likelihood of skeletal injuries. Athletes who display higher strength levels have repeatedly been cited as less likely to become injured.
Theoretical relationship between strength and performance
Absolute strength can be defined as the maximum amount of force that can be exerted, whilst relative strength can be defined as the maximum amount of force exerted per kg of body mass. Although there are no standards for strength levels (how strong is strong enough; how long is a piece of string?), a theoretical relationship has been proposed between relative back squat strength (strength per kg/lbs of body mass) and performance capabilities. Research has suggested three phases of strength levels: strength deficit, strength association and strength reserve (figure 2). In youth athletes, a theoretical timeline of 4-5 years of structured strength training indicates relative strength levels should be a minimum of 2x body mass for late adolescents (16-19 year olds), 1.5x body mass for adolescents (13-15 year olds) and 0.7x body mass for children (11-12 year olds). This is, of course, largely contextual to other performance factors and should be used as a guideline at best.
Figure 2: Theoretical relationship between back squat strength and performance capability.
With these theoretical guidelines, there is a pure focus on strength, and it does not take into consideration technical, tactical and psychological performance or otherwise. Anecdotally, what good is it if an athlete can back squat 2x their body mass but they can’t actually compete in their sport (as Keir Wenham-Flatt says, we want to create athletes that are PhD’s in their sport! Physical capabilities are great and definitely help, but we need to look at the holistic picture of sport performance and all it encompasses). Within context, by using the strength phase categorisation as a guide to categorising athletes accordingly, training can be prescribed to target adaptations to enhance their individual performance – another tool available for evidence-based practice. For example, if an athlete is within the strength deficit phase, they should focus on improving muscular strength to reap the additional benefits of higher levels of absolute and relative strength; if an athlete is in the strength reserve phase, they should focus on utilising their strength levels within other performance characteristics, such as muscular power.
Although elements of an athlete’s performance cannot be manipulated (for example, genetic profiles), sport scientists and strength & conditioning coaches can influence an athlete’s absolute and relative strength levels with strength training interventions. Higher levels of muscular strength can enhance force-time characteristics (for example, RFD and mechanical power) that can translate to athletic performance in tasks such as jumping, sprinting and change of direction tasks. While there may not be standardised strength levels for athletes to attain, it is recommended that athletes should strive to become as strong as possible within the context of their sport or event. The assessment of this can be aided with the use of theoretical guidelines of strength relative to performance.
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Suchomel, T. J., Nimphius, S., & Stone, M. H. (2016). The importance of muscular strength in athletic performance. Sports medicine, 46(10), 1419-1449.