Hip abductors and thigh muscles strength ratios and their relation to electromyography amplitude during split squat and walking lunge exercises

Background: The hip abductors (HAB), quadriceps (Q) and hamstrings (H) reciprocal strength ratios are predictors of electromyography (EMG) amplitude during load carrying walking at moderate intensity. Therefore, these strength ratios might predict also the EMG during the exercises as walking lunge (WL) or split squat (SSq) at submaximal intensity. Objective: To determine whether the EMG amplitude of vastus mediali (VM), vastus laterali (VL), biceps femoris (BF) and gluteus medius (Gmed) is associated with muscle strength ratio during SSqs and WLs. To determine whether the EMG amplitude differs between individuals with HAB/H ratio above and below one and between individuals with H/Q or HAB/Q ratio above and below 0.5 during SSqs and WLs. Methods: 17 resistance-trained men (age 29.6 ± 4.6 years) with at least 3 years of strength training performed in cross-sectional design 5 s maximal voluntary isometric contractions (MVIC) on an isokinetic dynamometer for knee extension, knee flexion, and hip abduction. The MVIC was used to normalize the EMG signal and estimate the individual strength ratios. Than participants performed WL and SSq for a 5 repetition maximum, to find out muscle activity at submaximal intensity of exercise. Results: The H/Q ratio was associated by Kendall’s tau (τ) with VM (τ = .33) and BF (τ = -.71) amplitude, HAB/Q ratio was associated with BF (τ = -.43) and Gmed (τ = .38) amplitude, as well as HAB/H was associated with VM (τ = -.41) and Gmed (τ = .74) amplitude. ANOVA results showed significant differences between SSq and WL (F(4, 79) = 10, p \u3c .001, ηp2 = .34) in Gmed amplitude, where WL resulted in higher Gmed amplitude compared to SSq. Other significant differences were found between H/Q groups (F(4, 29) = 3, p = .04, ηp2 = .28) in VM and Gmed amplitude, where group with H/Q \u3e 0.5 showed higher VMO amplitude and lower Gmed amplitude. Furthermore, significant difference was found for HAB/H groups (F(4, 29) = 4, p = .02, ηp2 = .34) in VM amplitude, where group with HAB/H \u3c 1 showed higher VM amplitude. Conclusions: The ratios of HAB, H and Q are able to predict Gmed, VM and BF activity during WL and SSq. WL resulted in higher activity level of Gmed than SSq, because WL includes the impact forces as part of lunge movement. WL should be used in resistance-training programme, if the strengthening of Gmed or VM is the aim

Journal of Human Kinetics / Isokinetic Strength profile of elite female handball players

Systematic assessment of muscle strength of the lower extremities throughout the annual training cycle in athletes is crucial from a performance perspective for the optimization of the training process, as well as a health perspective with regard to injury prevention. The main aim of the present study was to determine isokinetic muscle strength of the knee flexors and extensors in female handball players at the beginning of a preparatory period and to assess whether there were any differences between players of different performance levels. The performance level was expressed by means of membership of the Womens Junior National Handball Team (JNT, n=8) or the Womens National Handball Team (NT, n=9). The isokinetic peak torque during concentric and eccentric single-joint knee flexion and extension was measured at angular velocities of 60, 180, 240/s (concentric) and 60/s (eccentric). The Mann- Whitney test showed no significant differences in the peak torques or ipsilateral ratios between the two groups. The bilateral force deficit (BFD) for concentric extension at 240/s was significantly higher in the JNT compared with the NT (p=0.04; d=1.02). However, the results of individual evaluation show that the BFD was more frequent in the NT in most measurements. A high BFD was evident in the eccentric mode in both groups highlighting a need for particular strengthening. With regard to low strength ratios a prevention programme should be suggested for both observed groups of professional female handball players to reduce the risk of injury.(VLID)179426

Changes in Injury Risk Mechanisms After Soccer-Specific Fatigue in Male Youth Soccer Players

The aim of this study was to examine the acute effects of soccer specific fatigue on muscular and neuromuscular function in male youth soccer players. Elite soccer players (n = 20; age 15.7 ± 0.5 y; body height 177.75 ± 6.61 cm; body mass 67.28 ± 8.29 kg) were measured before and after soccer specific exercise (SAFT90). The reactive strength index (RSI) was determined by a drop jump test, leg stiffness (LS) by a 20 sub-maximal two-legged hopping test, and a functional hamstring to quadriceps strength ratio from isokinetic concentric and eccentric strength of the dominant and non-dominant leg (measured at angular velocities of 1.05 rad · s-1 and 3.14 rad · s-1). Metabolic response to the SAFT90 was determined by blood lactate and perceived exertion was assessed by the Borg scale. After simulated match play, a significant decrease in absolute LS (t = 4.411; p < 0.001; ω2 = 0.48) and relative LS (t = 4.326; p < 0.001; ω2 = 0.49) was observed and the RSI increased significantly (t = 3.806; p = 0.001; ω2 = 0.40). A reduction in LS found after the SAFT90 indicates possible reduction in dynamic knee stabilization. However, if we consider the changes in other observed variables, the present study did not clearly confirm that fatigue induced by a soccer specific protocol increased the risk of ACL and hamstring injury. This may be attributed to the simulated rather than actual match play used in the present study