This is a Guest Blog by Gloucester Rugby Strength & Conditioning Intern Jordan Murton

What is strength and why is it important?

Within sport, strength development is crucial during an athlete’s progression. Often strength levels of 1.5 – 2 times body weight being seen as the ‘holy grail’ in terms of being able to express an athlete’s true athletic potential. But what exactly is strength? If you wan to get stronger for rugby then keep reading!

Simply, strength is the body’s ability to apply muscular force against an external source of resistance such as gravity, an opposing player or an object such as a ball. As a result, it is no surprise that greater strength seems to have the ability to improve sporting performance as athletes participating at higher levels of competition are shown to be stronger (Baker & Newton, 2006). Relative strength (an athlete’s strength levels in regards to their body weight) is also linked to performance potential (Lawton, et al., 2011) with greater relative strength predicting greater performance potential. However, strength can also be defined as the ability to resist unwanted movement consequently having significant importance in increasing an athlete’s resilience to injury.

Current traditional strength training guidelines and general methods used to develop strength

Due to strength having great importance within sporting performance, both athletes and coaches need to be able to develop and progress strength levels by using training methods that will inflict the neural, muscular and skeletal adaptations resulting in increased strength.

A popular method to achieve this is resistance training. Current guidelines suggest that when training for muscular strength (see table below) an intensity of equal to or above 85% of one repetition maximum (1RM) should be used in a repetition range of 2-6. It also advises that a set range of 2-6 with a rest period of 2-5 minutes between sets should be employed.

There are typically four methods that are used to develop an individual’s maximal strength;

1. Maximal strength method
   • This method involves lifting at an intensity equal to or above 85% of 1RM
2. Submaximal effort method
   • This involves submaximal loads being lifted for low reps (indicated in the table above), under minimal fatigue with a focus on movement efficiency
3. The dynamic effort method
   • Within this method, submaximal loads are lifted with the focus on moving the load with maximum velocity
4. The repetition effort method
   • Submaximal loads lifted for repetitions at or close to failure

Learn a Simple Formula to Get Stronger For Rugby

Adaptations to strength training

Summary of strength training adaptations

• Increased force production
• Increased RFD
• Increased power
• Larger motor units recruited faster
• Increased rate of firing of motor units
• Increased hypertrophy
• Improvement in both inter- and intra-muscular coordination

Increased force production

Strength training results in the force of the force-velocity curve shifting to the right, caused by the athlete being able to produce larger amounts of force. This could also result in a greater resistance to fatigue being experienced due to a lower percentage of their 1RM being used to produce movements.

Neural adaptation 

When performing a movement, the brain is lazy as it will always use minimal effort to complete the task and result in smaller motor units are recruited first. This is explained by the size principle, as smaller motor units are recruited first due to their greater excitability (Dideriksen & Farina, 2013). Following a period of strength training, larger motor units are recruited faster due to greater firing rates of neurons. This is shown by greater muscle activation occurring faster and is suggested to be key in the development of force once motor unit recruitment is complete. This essentially aids in improving the rate of force development and greater levels are associated with strength training (Tillin, et al., 2013).

Rate of force development (RFD)

This can be defined as how much force we can exert in the first 250ms of a movement, or in layman’s terms, how fast we can express as much force as possible. Strength training has a number of effects that result in a greater rate of force development, one of which is an increased rate in which cross-bridge cycling occurs enabling our muscles to produce a greater force faster. Another effect strength training has on RFD  is that as previously mentioned, motor neuron firing frequency is increased resulting in greater muscle activation occurring much faster (Kamen & Knight, 2004). It is suggested that in order for strength training to have its greatest effect on RFD, movements must be performed with the greatest intent to produce the movement with the highest possible velocity rather than executing the movement in a slow manner (Young & Bilby, 1994).

Also, an increased RFD aids in increased maximal strength due to a greater impulse being produced (Holterman, et al., 2007). Impulse is a product of force and time, hence the greater force we can produce in a shorter time, the greater the impulse that will be manufactured.

Increased power

Increasing strength levels, directly and indirectly, increases power. Power is a product of force and velocity, therefore, increasing strength levels will enable for higher power outputs during maximal efforts, which could, in theory, increase maximum velocity. Also, increasing maximum strength levels ultimately reduces the intensity of submaximal efforts in relation to maximum capacity, thus this should enable for a greater repeatability of submaximal efforts.

Increased hypertrophy

Increasing the cross-sectional area (CSA) of a muscle results in an increase in the amount of force that a muscle is capable of producing (Saul, et al., 2015). For this reason, a strength training block of training proceeds a hypertrophy block within linear periodisation. A larger muscle causes a greater joint moment and reduces the joint’s angular displacement (Sugisaki, et al., 2015), resulting in greater strength capabilities for muscles with large CSA.

Improvement in coordination

When novice athletes first begin resistance training, they experience initial increases in strength levels which is a result of improvements in their coordination levels (Moritani, 1993) caused by the neural adaptations previously mentioned. Following this, further improvements in strength seem to be due to improvements in inter-muscular coordination (Almasbakk & Hoff, 1996). This is the ability of the central nervous system to coordinate the distribution of the neural drive to all muscles in an order and proportion that optimises the production of force when habitually performed.

Issue/difficulty in chasing strength gains in trained athletes

In the initial phases of training for a novice athlete, near enough any form of strength training will result in the desired adaptations. However, the greater your training age, the less general training works. A great analogy is to think of a tube of toothpaste. When it is first bought you can squeeze the tube anywhere (training methods) and toothpaste will come out (strength gains). However, the more you use it, the harder it is to get toothpaste out and you have to resort to squeezing the tube using different methods to get any results. The reason for general strength training no longer producing the desired outcomes, is that these methods do not provide enough of a stimulus to produce the adaptations (Ratamess, et al., 2009). Therefore, more advanced and variable methods should now be relied upon to develop strength levels.

Variable resistance methods for strength development

As with strength training in novices, there are still a number of methods that can be used to affect strength adaptations in athletes with a greater training age. One of these methods is variable resistance training, which utilises either elastic bands or chains in addition to traditional resistance training. Elastic bands may be used in numerous ways, to either provide assistance or added resistance at different stages during the lift (generally around the sticking point). When using them to assist the lift, the bands tend to be placed so that they stretch during the eccentric phase of a lift and recoil during the concentric phase to aid the athlete to move the resistance.

This method of utilising bands can be useful in encouraging increased rate of force development in the movement as the load is lighter and/or there is less tension at the beginning of the lift (Stevenson, et al., 2010). Bands may also be used to add greater resistance to the lift by reversing how the bands are placed when using them as an assistance, so that the bands stretch during the concentric phase, causing greatest tension towards the end of the concentric phase. Applying band resistance like this can further aid strength development due to an increase in muscular force and peak power production being required to complete the lift (Wallace, et al., 2006).

Also, this may trigger greater muscular activation during the lift’s eccentric phase due to the added tension caused from the band recoiling (Wilson & Kritz, 2014). The utilisation of chains also functions in the same way as bands to provide added resistance, as they are placed over the load and onto the floor. As the movement occurs the chains are slowly lifted off the floor during the concentric phase of the lift, increasing the load. As a result, chains tend to have the same effects as mentioned above, however, in addition, they can produce strength adaptations by increasing motor unit recruitment due to a greater emphasis on stabilisation factors (Berning, et al, 2004) caused by the chains swaying during the movement once they are completely lifted off the floor.

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References

Almasbakk, B. & Hoff, J., 1996. Coordination, the determinat of velocity specificity?. Journal of Applied Physiology , 81(5), p. 2046.

Baker, D. & Newton, R. U., 2006. Discrimativeanalyses of various upper body tests in professional rugby-league players. International Journal of Sports Physiology and Performance, 4(1), pp. 347-360.

Berning , J. M., Coker, C. A. & Adams, K. J., 2004. Using chains for strength and conditioning. Strength & Conditioning Journal , 26(5), pp. 80-84.

Diderikson, J. L. & Farina, D., 2013. Motor unit recruitment by size does not provide functional advantage for motor performance. The Journal of Physiology , 591(24), pp. 6139-6156.

Holterman, A., Roelevald, K., Vereijken, B. & Ettema, G., 2007. The effect of rate of force development on maximal force production: acute and training-related aspects. European Journal of Applied Physiology , 99(6), pp. 605-613.

Kamen , G. & Knight , C. A., 2004. Training-related adaptations in motor unit discharge rate in younger and older adults. The Journal of Gerontology – Biological Sciences and Medical Sciences, 59(12), pp. 1334-1338.

Lawton, T. W., Cronin, J. B. & McGuigan , M. R., 2011. Strength testing and training of rowers: A review. Sports Medicine, 41(5), pp. 413-432.

Moritani, T., 1993. Neuromuscular adaptations during the acquisition of muscular strength, power and motor tasks. Journal of Biomechanics , 26(1), pp. 95-107.

Ratamess , N. A. et al., 2009. American College of Sports Medicine Position Stand. Progression Models in resistance training for healthy adults. Medicine & science in Sports and Exercise, 41(3), p. 687.

Saul, K. R., Vidt, M. E., Gold, G. E. & Murray, W. M., 2015. Upper limb strength and muscle volume in healthy middle-aged adults. Journal of Applied Biomechanics, 31(1), pp. 484-491.

Stevenson , M. W. et al., 2010. Acute effects of elastic bands during the free-weight barbell back squat exercise on velocity, power and force production. The Journal of Strength & Conditioning Research , 24(11), pp. 2944-2954.

Sugisaki, N. et al., 2015. Influence of muscle hypertrophy on the moment arm of the triceps brachiimuscle. Journal of Applied Biomechanics, 31(1), pp. 111-116.

Tillin, N. A., Pain, M. T. G. & Folland , J., 2013. Explosive force production during isometric squats correlates with athletic performance in rugby union players. Journal of Sports Sciences, 31(1), pp. 66-76.

Wallace, B. J., Winchester , J. B. & McGuigan, M. R., 2006. Effects of elastic bands on force and power characteristics during the back squat exercise. The Journal of Strength & Conditioning Research , 20(2), pp. 268-272.

Wilson, J. & Kritz, M., 2014. Practical Guidelines and Considerations for the use of easticbands in strength and conditioning. Strength & Conditioning Journal , 36(5), pp. 1-9.

Young, W. B. & Bilby , G. E., 1993. The effect of voluntary effort to influence speed of contraction on strength, muscular power and hypertrophy development. The Journal of Strength & Conditioning Research, 7(3), pp. 172-178.