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Rate of force development

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Rate of force development (RFD) relates to the amount of force that a person can generate over a period of time. More force generated over a time period means that the RFD is higher. Maximum RFD is based upon the greatest amount of force developed in the shortest time. A high RFD is important in order to achieve faster and more powerful movements. For example, an ability to achieve a higher RFD will mean a person can jump higher than they would be able to do otherwise. The interaction of the neuromuscular system and the muscles is of particular importance in understanding the related physiological processes.[1]

Cross education effect

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When a person moves a limb, such as an arm, they will naturally move the other paired limb in tandem, in order to improve their overall sense of balance. As well as balancing the spatial positioning of the limbs, this involves balancing the agonist and antagonist forces of the limbs. These co-activating forces relate to a person’s centre of mass where the forces towards and away from the centre are approximately even and the person is in a state of postural equilibrium. This can be meant in regard to either static postures or dynamic movements.[2] It should be noted, that when a person moves, their centre of mass moves also in a unified process.[3] The stabilisation of the centre of mass in this regard, has a reciprocal benefit in that it enables the limbs to move from a more stable platform and thereby improves the efficiency of the movement.[4] Unilateral exercises can be particularly effective in improving a person’s ability to balance.[5]

In contrast to whole body balance, the cross-education effect is considered primarily in regard to situations where one limb is moving, the other limb concurrently activates but with limited, if any, perceptible movement. For example, a person is standing and they lift up their left arm while not moving their right. Even though the right arm does not perceptibly move, it is still activated by the movement of the left arm. The same phenomena applies for any form of limb movement, in that the other limb will also be activated.[6]

A form of unilateral training can be utilised which involves only the movement of one limb, with the other limb being non-moving. However, the non-trained limb also becomes stronger due to the cross-education effect.[7] Research conducted by Munn and colleagues, assessed that the untrained limb strengthened on average by 7.8% over a period of training, which is 35.1% of the strength gain experienced by the limb actually being trained.[8] How the nervous system activates in conjunction with the moving limb is considered to be of particular significance in in understanding the underlying causes of the effect, which are not as of yet fully understood.[9] In situations whereby one limb cannot be moved for some reason, the cross-education effect can be used to strengthen it, improve agility, and prevent muscle atrophy etc. This can make it useful for the rehabilitation of sports injury, training people with a lateral imbalance of motor skills, or mobility impairments such as that suffered by stroke victims who may not be able to use one side of their body.[10][11]








When a person moves a limb, they will naturally move the other limb in tandem in order to balance. As well as balancing the spatial positioning of the limbs, this involves balancing the agonist and antagonist forces of the limbs. These co-activating forces relate to a person’s centre of mass, or centre of gravity, where the forces towards and away from the centre are approximately even and they are said to be in balance. Noting, that when a person moves, their centre of mass moves also in a unified process.

Cross-education refers to when the act of one limb moving in regard to the other limbs movement, is, in terms of distance travelled, barely perceptible; but when considered in terms of stimulation of the corresponding nervous system and muscle, is perceptible, especially with modern measurement methods, such as EMGs. For example, a person is standing and they lift up their left arm while not moving their right. Even though the right arm does not perceptibly move, it is still activated by the movement of the left arm. The same phenomena applies for any form of movement; the other limb will be activated. Over a period of training using this method, the non-moving limb will become stronger. This effect is known as cross-education. A significant volume of research into the underlying cause of the effect, identifies the wider response of the nervous system to the moving arm as being of particular significance. Research suggests that a percentage strength increase of about 18% can be achieved in the non-moving limb.

In terms of standard sporting practice, it is not particularly employed because it is more usually more effective to move both limbs at the same time in order to improve balance and force production. However, in situations whereby one limb cannot be used for some reason, the cross-education effect can be used to strengthen the non-moving limb, improve agility, prevent atrophy etc. This can make it useful for the rehabilitation of sports injury and impairments such as that suffered by stroke victims who may not be able to use one side of their body. -- When a person moves a limb, such as an arm, they will naturally move the other paired limb in tandem, in order to balance. As well as balancing the spatial positioning of the limbs, this involves balancing the agonist and antagonist forces of the limbs. These co-activating forces relate to a person’s centre of mass, or centre of gravity, where the forces towards and away from the centre are approximately even and they are said to have a stable centre of mass or to be in balance- this is meant in regard to both static and dynamic balances. (source) It should be noted, that when a person moves, their centre of mass moves also in a unified process. (source) The strengthening of the centre of mass in this regard, has a reciprocal benefit in that it can then further enable the limbs to move from a more stable platform.

Unilateral exercises can be particular effective in training limbs to act as a form of balance for the other limb.

The cross-education effect, however, refers to how when one limb is moving, the other limb concurrently activates but with limited, if any, perceptible movement. A significant volume of research into the underlying cause of the effect, identifies how the nervous system activates in conjunction with the moving arm as being of particular significance. Multiple research studies suggest that a percentage strength increase of about 18% can be achieved in the non-moving limb in this manner.

In terms of standard sports training, the cross-education effect is not ordinarily employed because it is usually more effective to move both limbs at the same time in order to improve balance and force production. However, in situations whereby one limb cannot be moved for some reason, the cross-education effect can be used to strengthen it, improve agility, prevent atrophy etc. This can make it useful for the rehabilitation of sports injury and impairments such as that suffered by stroke victims who may not be able to use one side of their body.


File:President Ma meets Japan's Interchange Association Taipei Office Chief Representative Sumio Tarui 20120516 1010516馬英九總統接見日本交流協會台北事務所新任代表樽井澄夫1 (Flickr id 7208535402).jpg|thumb|President Ma meets Japan's Interchange Association Taipei Office Chief Representative Sumio Tarui 20120516 1010516馬英九總統接見日本交流協會台北事務所新任代表樽井澄夫1 (Flickr id 7208535402)

Totalitarianism and repression

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There is general consensus among academics that the GDR fulfilled most of the criteria to be considered a totalitarian state. There is, however, ongoing debate as to whether the more positive aspects of the regime can sufficiently dilute the harsher aspects so as to make the totalitarian tag seem excessive. According to the historian Mary Fulbrook:

‘Even those who are most critical of the concept admit that the regime possessed most, if not all, of the objective traits associated with the term, i.e. rule by a single party or elite that dominated the state machinery; that centrally directed and controlled the economy; mass communication, and all forms of social and cultural organisation; that espoused an official, all-encompassing, utopian (or, depending on one’s point of view, dystopian) ideology; and that used physical and mental terror and repression to achieve its goals, mobilise the masses, and silence opposition- all of which was made possible by the buildup of a vast state security service.’[12]

The state security service (SSD) was commonly known as the Stasi, and it was fundamental to the socialist leaderships attempts to reach their historical goal. It was an open secret in the GDR that the Stasi read people’s mail and tapped phone calls.[13] They also employed a vast network of unofficial informers who would spy on people more directly and report to their Stasi handlers. These collaborators were hired in all walks of life and had access to nearly every organisation in the country. At the end of the GDR in 1990 there were approximately 109, 000 still active informants at every grade. Repressive measures carried out by the Stasi can be roughly divided into two main chronological groupings: pre and post 1971 when Honecker came to power. According to the historian Nessim Ghouas, ‘There was a change in how the Stasi operated under Honecker in 1971. The more brutal aspects of repression seen in the Stalinist era (torture, executions, and physical repression descending from the GDR’s earlier days) was changed with a more selective use of power.’[14] The more direct forms of repression such as arrest and torture could mean significant international condemnation for the GDR. However, the Stasi still needed to paralyse and disrupt what it considered to be ‘hostile-negative’[15] forces (internal domestic enemies) if the socialist goal was to be properly realised. A person could be targeted by the Stasi for expressing politically, culturally, or religiously incorrect views; for performing hostile acts; or for being a member of a group which was considered sufficiently counter-productive to the socialist state to warrant intervention. As such, writers, artists, youth sub-cultures, and members of the church were often targeted.[16] If after preliminary research the Stasi found an individual warranted action against them then they would open an ‘operational case’[17] in regard to them. There were two desirable outcomes for each case: that the person was either arrested, tried, and imprisoned for an ostensibly justified reason, or if this could not be achieved that they were debilitated though the application of Zersetzung (transl. decomposition) methods. In the Honecker era, Zersetzung became the primary method of Stasi repression, due in large part to an ambition to avoid political fallout from wrongful arrest.[n 1] Zersetzung methods varied and were tailored depending on the individual being targeted. They are known to have involved sending offensive mail to a person’s house, the spreading of malicious rumours about them, banning them from traveling, sabotaging their career, breaking into their house and moving objects around etc. These acts could be intensely intimidating and confusing for the person targeted. They frequently led to unemployment, social isolation, and poor mental health. Many people had various forms of mental or nervous breakdown. Similarly to physical imprisonment Zersetzung methods had the effect of paralysing a person’s ability to operate but with the advantage of the source being unknown or at least unproveable. There is ongoing debate as to whether directed energy devices, such as X-ray transmitters, were used in combination with the psychological warfare methods of Zersetzung.[18] The historian Mike Dennis states that 'Between 1985-1988, the Stasi conducted about 4,500 t0 5,000 OVs (operational cases) per year.'[19] The International Rehabilitation Council for Torture Victims considers that there are between 300,000-500,000 victims of torture, Zersetzung, and gross human rights violations delivered by the Stasi.[20] In the modern day victims of historical Zersetzung can draw a special pension from the German state.[21]

A unilateral (single leg) barbell back squat.

Unilateral training

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Unilateral training

Unilateral training involves the performance of physical exercises using one limb instead of two. Such exercises should be considered as being distinct from their bilateral, two limbed, counterparts. For example, unilateral squats use one leg, and bilateral squats use two legs; a unilateral bench press uses one arm and a bilateral bench press two arms. Unilateral exercise is commonly involved in comprehensive training regimes and especially those of professional sports people. Usually it is used is in addition to bilateral training as opposed to instead of it. Unilateral training can yield numerous benefits including improving muscular balance in different sides of the body, improving a person’s sense of balance, helping to avoid or rehabilitate injury.

Sports specificity


Specific exercises Lower body Upper body

Muscular balance Muscle cross-education

Sense of balance


Unilateral training

Unilateral training involves the performance of physical exercises using one limb instead of two. Such exercises should be considered as being distinct from bilateral, two limbed, exercises. For example, unilateral squats use one leg, and bilateral squats use two legs. A unilateral bench press uses one arm and a bilateral bench press two arms. Depending on the exercise, this may also entail using different equipment i.e. a dumbbell instead of a barbell. Unilateral exercise is commonly involved in comprehensive training regimes and especially those of professional sports people and athletes. Usually it is used in addition to bilateral training as opposed to instead of it. Unilateral training can yield numerous benefits including improving a person’s muscle balance between the left and right sides of their body, improving their sense of balance, and helping to avoid or rehabilitate injury.[22]

Advantages

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Sports specificity

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Many sports require participants to perform actions with one limb instead of two. For example, a football player may kick the ball while standing on one leg, and a tennis player may hit the ball using a one-handed swing of their racket. The strengthening of the limbs in a unilateral fashion can help the players to perform these actions more effectively than if the limbs were trained in a bilateral fashion. This is because the unilateral action more closely resembles the sporting action, and, based upon the principle of specificity, benefits gained from it are more transferable to the performance of the sporting action.[23] Significantly, running is considered to be a unilateral action as it involves alternating between using the legs singly. Walking is also sometimes considered to be a unilateral action for this reason although it involves a bilateral element. Quick changes of direction during sport are also frequently performed in a unilateral manner.[24]

Muscle training focus

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As unilateral exercises emphasise muscle use in a different way to bilateral exercises, and thereby alter the ratio in which different muscles are engaged, they can be selected in order to focus on training particular muscles. For example, a one-legged squat activates the gluteus medius more than a bilateral squat. This makes it a recommended exercise for runners, where this muscle is considered to play a particularly important role.

Sense of balance

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Unilateral exercises may require a person to try harder to maintain their sense of balance during the exercise. As a result, their sense of balance overall may improve. This is especially the case in regard to single leg exercises. On this basis, unilateral exercises are considered to be highly functional, in that the improved sense of balance that they confer, transfers well to most sports and athletics where the participants are more likely to need to balance on one leg and perform an action, or move through a range of movement using only one leg as a base of support.[25]

Muscle balance

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Some people can have a significant muscle imbalance between the different sides of the body, including the limbs, meaning one side is excessively stronger than the other. This generally means that performance is impaired and injury risk is increased. Such an imbalance may be the result of lifestyle factors, such as sitting at a computer using a mouse, or from training in an imbalanced way, or for other reasons. It may not be resolved by bilateral training as it may continue during the exercise. Unilateral training may, however, mean that the person is definitely performing the same amount of work with either side of the body and this can therefore mean that the muscle imbalance is resolved. For example, if a person’s right leg is stronger than their left leg, and it therefore performs 60% of the work in a bilateral squat, and the left leg 40%, then the bilateral squat will not fix the imbalance. Moreover, even if the percentage discrepancy remained the same, as their overall strength increased, the discrepancy in terms of how much force could be applied would increase. Unilateral squats performed alternatively would, however, ensure that each leg was performing the same amount of work, meaning that the strength of each leg becomes more similar to the strength of the other leg, and the muscle imbalance is reduced. As it is reduced, performance improves and the risk of injury is reduced.[26]

Core strength

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Due to the fact that unilateral exercises are usually performed more to one side than the other, relative to a person’s centre of mass, their performance necessitates different, and generally increased, core activity in order to provide the appropriate stability during the exercise. For example, a one-handed lift of a weight over a person’s head, requires them to stabilise their core in a different way than if they were lifting a barbell over their head with two-hands. Generally, this means that they have to work harder to stabilise the weight and themselves during the lift, meaning greater levels of core activation.[27]

Injury prevention

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As unilateral exercises can improve a person’s sense of balance, correct muscle imbalances and improve the harmonious functioning of the muscular system, and transfer effectively to the performance of sports specific movements, they can also help to prevent injury as the practitioner becomes more capable and stronger in general, than if they only performed bilateral exercises.[28]

Rehabilitation

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Unilateral exercises may be used in rehabilitation programmes. For example, single leg balances may be used to strengthen someone’s ankle after they recover from an injury and thereby help to restore their ability to balance.[29]

Disadvantages

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If unilateral exercise is used instead of a bilateral exercise, or vice versa, then this can yield a negative training outcome overall. This is because even though unilateral and bilateral exercises may yield similar results, there can be significant differences and the use of one and not the other may mean potentially advantages outcomes are lost. For example, the incorporation of a unilateral barbell squat into a training regime, but not a bilateral barbell squat, may mean that only half the weight can be lifted. And so while the legs may be exercised to a similar amount in both types of squat, in the bilateral squat the core is forced to work significantly harder which may help to achieve greater levels of core strength. The most common solution is to incorporate both bilateral and unilateral exercises in a training regime in order to gain the advantages of both types of exercise. The ratio of unilateral to bilateral exercises can be adjusted based upon the specific requirements of the training regime.[30]

See also

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Deadlift variations

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  • Stiff legged deadlift
  • Romanian deadlift
  • Single-leg Romanian deadlift
  • Trap bar deadlift
  • Variable Resistance
  • Partial

Sources

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  • ACSM's Foundation of Strength and Conditioning
  • Encyclopedia of Muscle and Strength
  • Getting Stronger Weight Training for Sports
  • Designing Resistance Training Programmes


References

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  1. ^ Knudson, Duane (2003). Fundamentals of Biomechanics. New York: Springer Science + Business Media. p. 88. ISBN 978-1-4757-5300-4.
  2. ^ Vega, Jose A. & Cobo, Juan (2021). Prorioception. London: IntechOpen. pp. 21–24. ISBN 978-1-83968-070-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  3. ^ Thatcher, Joanne; Thatcher, Rhys; Day, Melissa; Portas, Matthew; Hood, Simon (2009). Sport and Exercise Science. Exeter: Learning Matters. pp. 192–93. ISBN 9781844451876.{{cite book}}: CS1 maint: multiple names: authors list (link)
  4. ^ Jones, Karen J. (2011). Neurological Assessment E-book: A Clinician's Guide. London: Elsevier. p. 217. ISBN 978-0-7020-4052-8.
  5. ^ Swinnen, Bram (2016). Strength Training for Soccer. Abingdon: Routledge. p. 104. ISBN 978-1-315-66527-6.
  6. ^ McCall, Pete (2022). "The Benefits of Unilateral Training". Ageless Intensity: High-Intensity Workouts to Slow the Aging Process. Chamapign: Human Kinetics. ISBN 978-1-7182-0075-3.
  7. ^ Zatsiorsky, V. (2000). Biomechanics in Sport: Performance Enhancement and Injury Prevention. Oxford: Blackwell Publishing. p. 9. ISBN 0-632-05392-5.
  8. ^ Enoka, Roger M. (2008). Neuromechanics of Human Movement. Champaign: Human Kinetics. p. 364. ISBN 0-7360-6679-9.
  9. ^ Astrand, Per-Olaf; Rodahl, Kaare; Dahl, Hans A.; Stromme, Sigmund B. (2003). Textbook of Work Physiology: Physiological Bases of Exercise (4 ed.). Human Kinetics. p. 326. ISBN 0-7360-0140-9.{{cite book}}: CS1 maint: multiple names: authors list (link)
  10. ^ Dietz, Volker & Ward, Nick. Oxford Textbook of Neurorehabilitation. Oxford: Oxford University Press. ISBN 978-0-19-967371-1.{{cite book}}: CS1 maint: multiple names: authors list (link)
  11. ^ Kidgell, Dawson J & Pearce, Alan J. (2020). Principles of Exercise Neuroscience. Cambridge: Cambridge Scholars Publishing. p. 231. ISBN 1-5275-5813-4.{{cite book}}: CS1 maint: multiple names: authors list (link)
  12. ^ Fulbrook, Mary (2015). Becoming East German: Socialist Structures and Sensibilities After Hitler. Berghahn books. p. 3. ISBN 9781785330278.
  13. ^ Ghouas, Nessim (2004). The Conditions Means and Methods of the MfS in the GDR: An Analysis of the Post and Telephone Control. Cuvillier Verlag. p. 58. ISBN 3898739880.
  14. ^ Ghouas, Nessim (2004). The Conditions Means and Methods of the MfS in the GDR: An Analysis of the Post and Telephone Control. Cuvillier Verlag. p. 59. ISBN 3898739880.
  15. ^ Dennis, Mike (2003). "Tackling the enemy- quiet repression and preventive decomposition". The Stasi: Myth and Reality. Pearson Education Limited. p. 112. ISBN 0582414229.
  16. ^ Dennis, Mike (2003). "Tackling the enemy- quiet repression and preventive decomposition". The Stasi: Myth and Reality. Pearson Education Limited. p. 114. ISBN 0582414229.
  17. ^ Dennis, Mike (2003). "Tackling the enemy- quiet repression and preventive decomposition". The Stasi: Myth and Reality. Pearson Education Limited. p. 114. ISBN 0582414229.
  18. ^ Fulbrook, Mary (2008). The People's State: East German Society from Hitler to Honecker. New Haven: Yale University Press. p. 245. ISBN 9780300144246.
  19. ^ Dennis, Mike (2003). "Tackling the enemy- quiet repression and preventive decomposition". The Stasi: Myth and Reality. Pearson Education Limited. p. 114. ISBN 0582414229.
  20. ^ "After the fall: The hidden trauma behind the Berlin Wall". irct.org. IRCT. Retrieved 9 September 2021.
  21. ^ Oltermann, Philip. "'I've been shafted twice': Stasi victims and their quest for compensation". The Guardian. Retrieved 9 September 2021.
  22. ^ Swinnen, Bram (2016). Strength Training for Soccer. London: Routledge. p. 269. ISBN 978-1-315-66527-6.
  23. ^ Timothy R. Ackland; Bruce C. Elliot; John Bloomfield (2009). Applied Anatomy and Biomechanics in Sport. Champaign: Human Kinetics. p. 135. ISBN 978-0-7360-6338-8.{{cite book}}: CS1 maint: multiple names: authors list (link)
  24. ^ Moir, Gavin L. (2016). Strength and Conditioning: A Biomechanical Approach. Burlington: Jones & Bartlett Learning. p. 245. ISBN 978-1-284-03484-4.
  25. ^ Boyle, Michael (2016). "Making training more functional". New Functional Training for Sports (2 ed.). Champaign: Human Kinetics. ISBN 9781492530626.
  26. ^ Bishop, Tim (2012). "Unilateral training for balanced strength". Stronger Legs and Lower Body. Champaign: Human Kinetics. ISBN 978-0-7360-9295-1.
  27. ^ Brent A. Alvar; Katie Sell; Patricia A. Deuster (2017). "Unilateral and bilateral exercise performance". NSCA's Essentials of Tactical Strength and Conditioning. Champaign: Human Kinetics. p. 164. ISBN 9781492546146.{{cite book}}: CS1 maint: multiple names: authors list (link)
  28. ^ Bishop, Tim (2012). "Unilateral training for balanced strength". Stronger Legs and Lower Body. Champaign: Human Kinetics. ISBN 978-0-7360-9295-1.
  29. ^ Brotzman, S. Brent (2011). "Foot and Ankle Injuries". Clinical Orthopaedic Rehabilitation (3 ed.). Elsevier Mosby. p. 362. ISBN 978-0-323-05590-1.
  30. ^ Timothy R. Ackland; Bruce C. Elliot; John Bloomfield (2009). Applied Anatomy and Biomechanics in Sport. Champaign: Human Kinetics. p. 135. ISBN 978-0-7360-6338-8.{{cite book}}: CS1 maint: multiple names: authors list (link)


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