Purpose The aim of the research was to determine how knee extensor strength asymmetry influences gait asymmetry and variability since these gait parameters have been related to mobility and falls in older adults. Methods Strength of the knee extensors was measured in 24 older women (65 – 80 yr). Subjects were separated into symmetrical strength (SS, n = 13) and asymmetrical strength (SA, n = 11) groups using an asymmetry cutoff of 20%. Subjects walked at a standard speed of 0.8 m s−1 and at maximal speed on an instrumented treadmill while kinetic and spatiotemporal gait variables were measured. Gait and strength asymmetry were calculated as the percent difference between legs and gait variability as the coefficient of variation over twenty sequential steps. Results SA had greater strength asymmetry (27.4 ± 5.5%) than SS (11.7 ± 5.4%, P < 0.001). Averaged across speeds, SA had greater single (7.1% vs. 2.5%) and double-limb support time asymmetry (7.0 vs. 4.3%) than SS and greater single-limb support time variability (9.7% vs. 6.6%, all P < 0.05). Group × speed interactions occurred for weight acceptance force variability (P = 0.02) and weight acceptance force asymmetry (P = 0.017) with greater variability at the maximal speed in SA (5.0 ± 2.4% vs. 3.7 ± 1.2%) and greater asymmetry at the maximal speed in SA (6.4 ± 5.3% vs. 2.5 ± 2.3%). Conclusion Gait variability and asymmetry are greater in older women with strength asymmetry and increase when they walk near their maximal capacities. The maintenance of strength symmetry, or development of symmetry through unilateral exercise, may be beneficial in reducing gait asymmetry, gait variability, and fall risk in older adults.

The goal of this study was to examine the relationship between kinematics, motor abilities, anthropometric characteristics, and the initial (10 m) and secondary (30 m) acceleration phases of the 100 m sprint among athletes of different sprinting performances. Eleven competitive male sprinters (10.96 s ± 0.36 for 100 with 10.50 s fastest time) and 11 active students (12.20 s ± 0.39 for 100 m with 11.80 s fastest time) volunteered to participate in this study. Sprinting performance (10 m, 30 m, and 100 m from the block start), strength (back squat, back extension), and jumping ability (standing long jump, standing five-jumps, and standing ten-jumps) were tested. An independent t-test for establishing differences between two groups of athletes was used. The Spearman ranking correlation coefficient was computed to verify the association between variables. Additionally, the Ward method of hierarchical cluster analysis was applied. The recorded times of the 10 and 30 m indicated that the strongest correlations were found between a 1-repetition maximum back squat, a standing long jump, standing five jumps, standing ten jumps (r = 0.66, r = 0.72, r = 0.66, and r = 0.72), and speed in the 10 m sprint in competitive athletes. A strong correlation was also found between a 1-repetition maximum back squat and a standing long jump, standing five jumps, and standing ten jumps (r = 0.88, r = 0.87 and r = 0.85), but again only for sprinters. The most important factor for differences in maximum speed development during both the initial and secondary acceleration phase among the two sub-groups was the stride frequency (p<0.01).

The purpose of this investigation was to compare and determine the relevance of the morphological characteristics and variability of running speed parameters (stride length and stride frequency) between Usain Bolt’s three best 100 m performances. Based on this, an attempt was made to define which factors determine the performance of Usain Bolt’s sprint and, therefore, distinguish him from other sprinters. We analyzed the previous world record of 9.69 s set in the 2008 Beijing Olympics, the current record of 9.58 s set in the 2009 Berlin World Championships in Athletics and the O lympic record of 9.63 s set in 2012 London Olympics Games by Usain Bolt. The application of VirtualDub Programme allowed the acquisition of basic kinematical variables such as step length and step frequency parameters of 100 m sprint from video footage provided by NBC TV station, BBC TV station. This data was compared with other data available on the web and data published by the Scientific Research Project Office responsible on behalf of IAAF and the German Athletics Association (DVL). The main hypothesis was that the step length is the main factor that determines running speed in the 10 and 20 m sections of the entire 100 m distance. Bolt’s anthropometric advantage (body height, leg length and liner body) is not questionable and it is one of the factors that makes him faster than the rest of the finalists from each three competitions. Additionally, Bolt’s 20 cm longer stride shows benefit in the latter part of the race. Despite these factors, he is probably able to strike the ground more forcefully than rest of sprinters, relative to their body mass, therefore, he might maximize his time on the ground and to exert the same force over this period of time. This ability, combined with longer stride allows him to create very high running speed - over 12 m/s (12.05 – 12.34 m/s) in some 10 m sections of his three 100 m performances. These assumption confirmed the application of Ballerieich’s formula for speed development. In most 10 m sections of the 100 m sprint, the step length was the parameter that significantly determined the increase of maximal running speed, therefore, distinguishing Bolt from the other finalists.

Čoh, M, Vodičar, J, Žvan, M, Šimenko, J, Stodolka, J, Rauter, S, and Maćkala, K. Are change-of-direction speed and reactive agility independent skills even when using the same movement pattern? J Strength Cond Res 32(7): 1929-1936, 2018-The purpose of this investigation was to determine whether there are differences between the 2 approaches to quantifying agility (preplanned vs. unplanned response) when reacting to a stimulus in an identical spatial scenarios. The study involved 45 male and 31 female trained athletes (age 21.2 ± 1.78 and 20.6 ± 1.27 years, body height 181.6 ± 8.31 and 167.7 ± 5.03 cm, and body mass 78.9 ± 11.33 and 63.3 ± 8.65 kg, respectively). A light-based reactive training system was used to measure the time to completion in a task that assessed agility by change-of-direction speed (CODS) in a preplanned condition and reactive agility (RA) in an unplanned condition across 4 spatial configurations. Sprint performance in a 30-m sprint and lower limb reactive power in a 10-m single leg jump test was also measured. Significant differences (p ≤ 0.05) were found between men and women in all tests and between performance in the CODS and RA condition for each spatial configuration. Significant correlations were observed between 30-m starting sprint speed and CODS and RA performance measured in a semicircle (r = 0.62, r = 0.60) and lateral (r = 0.54, r = 0.58) configuration in male athletes. The present findings suggest that CODS and RA are 2 different and independent skill domains that define agility. These qualities should be diagnosed by discrete assessments and enhanced by different training methodologies.

Knee strength ratios are related to the movement patterns, sport-specific training and knee injuries in athletes. The purpose of this study was to determine the ratios in the concentric isokinetic strength of the hamstrings and quadriceps and the isometric strength of the knee extensors. In female basketball players (n = 14) and female volleyball players (n = 12) were evaluated: the hamstrings to quadriceps peak torque ratio (H/Q) and side-to-side peak torque ratio (TR) for hamstrings and quadriceps; the ratio of the maximal bilateral strength to the summed maximal unilateral strength (B/U) and side-to-side maximal strength ratio (SR) for knee extensors. For the H/Q values, a 2 × 2 × 3 mixed-factorial analysis of variance and Bonferroni post hoc test were computed. The H/Q values increased from 48.0 (3.9)% at 60°/s to 70.4 (7.9)% at 300°/s. Furthermore, there were significant differences in the H/Q values between 300°/s and 180°/s, 300°/s and 60°/s in basketball and volleyball athletes, and between 180°/s and 60°/s only in basketball athletes (p < .05). Significantly higher H/Q results at 60°/s demonstrated basketball players than volleyball players (p < .05). Differences in the TR and SR mean values ranged from 4.4% to 8.6% and indicated no significant side-to-side strength deficits (p > .05). In both groups, greater isometric strength developed bilaterally was found (B/U > 100%). The findings revealed the magnitude of knee strength ratios in female athletes determined by sport-specific movements in basketball and volleyball. This study highlighted the importance of the bilateral strength deficit and muscular balance between the hamstrings and quadriceps in basketball and volleyball athletes in activities related to their movement patterns and specific training.