Obesity is associated with functional limitations in muscle performance and increased likelihood of developing a functional disability such as mobility, strength, postural and dynamic balance limitations. The consensus is that obese individuals, regardless of age, have a greater absolute maximum muscle strength compared to non-obese persons, suggesting that increased adiposity acts as a chronic overload stimulus on the antigravity muscles (e.g., quadriceps and calf), thus increasing muscle size and strength. However, when maximum muscular strength is normalised to body mass, obese individuals appear weaker. This relative weakness may be caused by reduced mobility, neural adaptations and changes in muscle morphology. Discrepancies in the literature remain for maximal strength normalised to muscle mass (muscle quality) and can potentially be explained through accounting for the measurement protocol contributing to muscle strength capacity that need to be explored in more depth such as antagonist muscle co-activation, muscle architecture, a criterion valid measurement of muscle size and an accurate measurement of physical activity levels. Current evidence demonstrating the effect of obesity on muscle quality is limited. These factors not being recorded in some of the existing literature suggest a potential underestimation of muscle force either in terms of absolute force production or relative to muscle mass; thus the true effect of obesity upon skeletal muscle size, structure and function, including any interactions with ageing effects, remains to be elucidated.

Following high profile, life changing long term mental illnesses and fatalities in sports such as skiing, cricket and American football-sports injuries feature regularly in national and international news. A mismatch between equipment certification tests, user expectations and infield falls and collisions is thought to affect risk perception, increasing the prevalence and severity of injuries. Auxetic foams, structures and textiles have been suggested for application to sporting goods, particularly protective equipment, due to their unique form-fitting deformation and curvature, high energy absorption and high indentation resistance. The purpose of this critical review is to communicate how auxetics could be useful to sports equipment (with a focus on injury prevention), and clearly lay out the steps required to realise their expected benefits. Initial overviews of auxetic materials and sporting protective equipment are followed by a description of common auxetic materials and structures, and how to produce them in foams, textiles and Additively Manufactured structures. Beneficial characteristics, limitations and commercial prospects are discussed, leading to a consideration of possible further work required to realise potential uses (such as in personal protective equipment and highly conformable garments).

Mechanical loading is thought to be a determinant of bone mass and geometry. Both ground reaction forces and tibial strains increase with running speed. This study investigates the hypothesis that surrogates of bone strength in male and female master sprinters, middle and long distance runners and race-walkers vary according to discipline-specific mechanical loading from sedentary controls.Bone scans were obtained by peripheral Quantitative Computed Tomography (pQCT) from the tibia and from the radius in 106 sprinters, 52 middle distance runners, 93 long distance runners and 49 race-walkers who were competing at master championships, and who were aged between 35 and 94 years. Seventy-five age-matched, sedentary people served as control group.Most athletes of this study had started to practice their athletic discipline after the age of 20, but the current training regime had typically been maintained for more than a decade. As hypothesised, tibia diaphyseal bone mineral content (vBMC), cortical area and polar moment of resistance were largest in sprinters, followed in descending order by middle and long distance runners, race-walkers and controls. When compared to control people, the differences in these measures were always > 13% in male and > 23% in female sprinters (p < 0.001). Similarly, the periosteal circumference in the tibia shaft was larger in male and female sprinters by 4% and 8%, respectively, compared to controls (p < 0.001). Epiphyseal group differences were predominantly found for trabecular vBMC in both male and female sprinters, who had 15% and 18% larger values, respectively, than controls (p < 0.001). In contrast, a reverse pattern was found for cortical vBMD in the tibia, and only few group differences of lower magnitude were found between athletes and control people for the radius.In conclusion, tibial bone strength indicators seemed to be related to exercise-specific peak forces, whilst cortical density was inversely related to running distance. These results may be explained in two, non-exclusive ways. Firstly, greater skeletal size may allow larger muscle forces and power to be exerted, and thus bias towards engagement in athletics. Secondly, musculoskeletal forces related to running can induce skeletal adaptation and thus enhance bone strength.

The impact of using different resistance training (RT) kinematics, which therefore alters RT mechanics, and their subsequent effect on adaptations remain largely unreported. The aim of this study was to identify the differences to training at a longer (LR) compared with a shorter (SR) range of motion (ROM) and the time course of any changes during detraining. Recreationally active participants in LR (aged 19 ± 2.6 years; n = 8) and SR (aged 19 ± 3.4 years; n = 8) groups undertook 8 weeks of RT and 4 weeks of detraining. Muscle size, architecture, subcutaneous fat, and strength were measured at weeks 0, 8, 10, and 12 (repeated measures). A control group (aged 23 ± 2.4 years; n = 10) was also monitored during this period. Significant (p > 0.05) posttraining differences existed in strength (on average 4 ± 2 vs. 18 ± 2%), distal anatomical cross-sectional area (59 ± 15 vs. 16 ± 10%), fascicle length (23 ± 5 vs. 10 ± 2%), and subcutaneous fat (22 ± 8 vs. 5 ± 2%), with LR exhibiting greater adaptations than SR. Detraining resulted in significant (p > 0.05) deteriorations in all muscle parameters measured in both groups, with the SR group experiencing a more rapid relative loss of postexercise increases in strength than that experienced by the LR group (p > 0.05). Greater morphological and architectural RT adaptations in the LR (owing to higher mechanical stress) result in a more significant increase in strength compared with that of the SR. The practical implications for this body of work follow that LR should be observed in RT where increased muscle strength and size are the objective, because we demonstrate here that ROM should not be compromised for greater external loading.

Enhanced muscle in vivo (and somewhat IGF-1) adaptations to resistance training are concurrent with muscle stretch, which warrants its inclusion within training.