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Physical and Physiological Reponses and Adaptations
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
Factors such as gross muscle architecture, angle of pennation, muscle insertion point, height, limb length, and moment arm may alter the mechanical advantage of the intact muscle lever system. For example, weightlifters possess a high ratio of body mass to height (BM h-1) compared to untrained subjects and other athletic groups. This BM h-1 is advantageous because it can provide an increased force production. This advantage is associated with the strong positive relationship between a muscle’s physiological cross-sectional area and maximum muscle force-generating capabilities (75). If two athletes of different heights and different limb lengths have the same muscle mass and volume, the shorter athlete will have the greatest muscle cross-section and therefore, greater force production.
Exercise Training, Mitochondrial Adaptations, and Aging
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Nashwa Cheema, Matthew Triolo, David A. Hood
After the age of 50, a person loses 0.5–1% of muscle mass per year, resulting in a 40% decrease by 80 years old, and a 2- to 3-fold increase in functional disability (13). The elderly population (>65 years) with the least muscle strength are also at a higher risk of mortality, suggesting that strength is a strong predictor of healthy ageing (141). The age-related decline of strength can be attributed to multiple factors. Aged tissue is morphologically very different from young muscle. Alterations in muscle architecture such as increased fat infiltration and connective tissue reduce the overall quality of muscle (160). Single fibres have been isolated from muscle biopsies of young and old men, and the maximal force was reduced in aged myofibres (51). Contractile function is further exacerbated by muscle atrophy. In humans, the decline in muscle mass is due to a decrease in fibre number and an increase in fibre atrophy (99). Rodent studies indicate that the most significant declines in muscle mass are observed in the quadriceps muscles, with a concomitant decline in fibre number (24).
Power versus endurance
Published in Francesco E. Marino, Human Fatigue, 2019
The strength and power disparity between human and extant non-human primates is confirmation that humans are adapted for endurance rather than power. The reasons for this apparent difference are complex and, as already discussed (see Chapter 3, Table 3.1), the muscle architecture plays a significant role. For example, the skeletal muscle fascicle length in humans is comparatively short when expressed as a ratio of body mass even though the human lower limb is a component of a higher percentage of total mass. Since fascicle length determines the number of sarcomeres where the contractile elements are located, the number of sarcomeres plays an important role in muscle shortening and force production. This suggests that power generation in the lower limbs of chimps is likely to be a function of the muscle, neurological and skeletal architecture, not muscle mass per se. In essence, to understand the physical power differential that exists between humans and other living primates it is necessary to consider in detail the following characteristics (Walker 2009): body mass distribution, moment arm differences, motor control of limb muscles and the quantity of white and grey matter within different areas of the nervous system.
The relationship between eccentric hamstring strength and dynamic stability in elite academy footballers
Published in Science and Medicine in Football, 2021
David Rhodes, Josh Jeffrey, Joe Maden-Wilkinson, Antony Reedy, Erin Morehead, John Kiely, Daniel Birdsall, Chris Carling, Jill Alexander
It is well documented throughout literature that muscle architecture is key to reducing hamstring injury risk (Opar et al. 2013). Findings within the present study showed no significant relationships between any stability parameter and Ɵ. An explanation of this through observation of potential differences in position and resultant muscle length when performing the two tests may be relevant. Consideration to the mechanism of injury for hamstring and ACL provides a potential explanation as to why no relationship was found in the current study. However, further research in this area would be required. Research indicates that the ACL is the most commonly injured ligament in the knee (Silvers-Granelli et al. 2017), with increases in re-rupture and poor return of the athlete to the same level pre-injury (Walden et al. 2016). Common mechanisms associated with ACL are linear motions from either a rapid acceleration or deceleration or excessive anterior force through the knee joint (Alentorn-Geli et al. 2009). The findings in the current research highlight relationships between higher eccentric strength scores and lower dynamic stability scores, with the exception of AP stability and Ɵ. Consideration, therefore, that increased eccentric strength has a positive influence on stability of the knee is suggested. Further research in this area should focus its attention on intervention training protocols to examine their effect on key aetiological contributors to injury.
Measuring biomechanical loads in team sports – from lab to field
Published in Science and Medicine in Football, 2020
Jasper Verheul, Niels J. Nedergaard, Jos Vanrenterghem, Mark A. Robinson
During training and match-play in football and other (team) sports, the different hard- and soft-tissues of the body are exposed to an array of forces. These forces cause mechanical tension within the tissues in the form of stresses and strains that, together with exercise-induced microdamage and metabolic stress, trigger remodelling and repair responses. Examples of such adaptations include alterations in muscle architecture (Nimphius et al. 2012; Secomb et al. 2017), changes in tendon stiffness and structure (Couppe et al. 2008; Mersmann et al. 2017; Esmaeili et al. 2017; Rabello et al. 2019), and increased bone mass and mineral density (Fredericson et al. 2007; Helge et al. 2014), which are generally considered desirable characteristics for enhanced performance (e.g., higher force production, increased storage and return of elastic energy). Excessive exposure to stresses and strains on the other hand can outpace repair mechanisms and cause an accumulation of micro-damage that weakens the tissues over time. This progressive weakening can ultimately lead to mechanical fatigue and tissue failure, such as muscle tears, tendon rupture or bone fractures (Bertelsen et al. 2017; Edwards 2018). The optimal loading thresholds of individual tissues depend on many factors, including tissue properties and loading history. In an ideal world, one would thus want to quantify and monitor the accumulation of tissue-specific stresses and strains over time.
The effectiveness of extracorporeal shock wave therapy to reduce lower limb spasticity in stroke patients: a systematic review and meta-analysis
Published in Topics in Stroke Rehabilitation, 2020
Rosa Cabanas-Valdés, Jordi Calvo-Sanz, Gerard Urrùtia, Pol Serra-Llobet, Albert Pérez-Bellmunt, Ana Germán-Romero
Range of motion was measured in eight studies28–30,33–36,38 by a goniometer (digital or manually) although there were differences in the measures reported in relation to: active/passive movement, total/dorsiflexion range, and the knee position as it influences soleus or gastrocnemius extensibility (see Table 9). Peak torques and torque threshold angles were measured by dynamometry in two studies.35,38 In relation to muscle architecture, such as fiber and fascicle length, perimeters, and fiber angles, three studies32,34,36 assessed them mainly by ultrasonography (echography). This method uses high-frequency sound waves to image internal body structures or objects, and currents that are underwater. Other studies also measured foot contact area30 and tension of the medialis gastrocnemius,37 evaluated by a myotonometer48 (see Table 10).