BACKGROUND: Intrinsic foot muscle (IFM) dysfunction and poor foot arch are associated with various foot conditions. Toe flexor exercise (TFE) has been used to improve it; however, the immediate effects of TFE on each IFM and how it relates to changes in navicular bone height (NH) are unclear. OBJECTIVE: This study aimed to investigate acute muscle swelling in the IFM after TFE and the association between changes in NH and IFM size. METHODS: Fourteen adults participated in this study. NH and cross-sectional area (CSA) of the IFM were acquired pre and post- TFE. The CSA of the IFM, including the abductor hallucis (AbH), flexor hallucis brevis, flexor digitorum brevis, and quadratus plantae, was acquired with ultrasonography. In the TFE, each participant completed five sets of eight repetitions with maximum strength. RESULTS: The NH and CSA of all IFM significantly increased significantly post-TFE (p< 0.01). Only the increase in AbH was moderately and positively correlated with the change in NH (r= 0.54, p< 0.01). CONCLUSION: This study suggests that the acute swelling of AbH after TFE is associated with an immediate increase in NH, supporting the important role of AbH in the formation of foot arch.

BACKGROUND: Deadlift (DL) and back squat (BSQ) are considered different exercises because of their kinematic and kinetic characteristics. However, there are similarities, such as joint movement and the maximal muscle strength generated. Although there are differences and similarities, it is unclear which is more related to athletic performance. OBJECTIVE: This study aimed to determine the relationship between DL and jump, acceleration, and change of direction and compare whether DL or BSQ differ in their relationship to jumping, acceleration, and change of direction. METHODS: Eighty male volleyball players (age: 19.6 ± 0.9 years, height: 179.2 ± 6.7 cm, mass: 71.9 ± 9.4 kg) volunteered to participate in this study. Countermovement jump (CMJ), 10-m sprint, and 1–5 repetition maximum (1–5 RM) BSQ were measured on day 1. The T-test and 1–5 RM DL were measured on day 2. RESULTS: DL had a significant and moderate relationship with all parameters of CMJ (r= 0.328, p< 0.01), 10-m sprint (r=-0.471, p< 0.01), and T-test (r=-0.441, p< 0.01). BSQ showed a significant and moderate relationship with the 10-m sprint (r=-0.489, p< 0.01) and T-test (r=-0.356, p< 0.01), but a significant and weak relationship only with CMJ (r=- 0.289, p< 0.01). In addition, no significant differences were found in the comparison of correlation coefficients (p> 0.05). CONCLUSIONS: Deadlift may be introduced as an alternative exercise to BSQ when there are limitations in the training environment, such as the lack of a squat rack to safely perform BSQ or home confinement due to external factors like pandemics.

BACKGROUND: Postactivation potentiation (PAP) enhances contractility of skeletal muscle whereas fatigue deteriorates it. Available evidence suggests that the two phenomena may express differently in endurance and power athletes. OBJECTIVE: To compare the patterns of change in knee muscle contractility induced by PAP and fatigue between endurance and power athletes. METHODS: Eleven endurance and ten power athletes (age: 18–33 years) performed isokinetic fatigue and isometric PAP protocols with knee extensors and flexors on computerised dynamometer. Tensiomyography (TMG) of the vastus medialis and semitendinosus muscle medialis was performed before the protocols and during a 10-min recovery. RESULTS: The changes in TMG profile were most pronounced in the vastus medialis of power athletes following the PAP protocol and least pronounced in the semitendinosus of the endurance athletes following the fatigue protocol. The differences between athlete types were most significant for the time-domain TMG parameters of vastus medialis. A significant correlation (r= 0.51–0.73) between the fatigue indices and changes in TMG parameters was observed for the vastus medialis muscle only. CONCLUSIONS: The results show that the TMG patterns of PAP and fatigue in the vastus muscle differ between endurance and power athletes. In this muscle, the changes in TMG parameters are also strongly associated with the degree of fatigue.

BACKGROUND: Foam roller with vibration is a recent development and its implementation has not yet been provided with a sufficient scientific justification. Information on whether an implementation of vibration foam rolling for self-massage before the powerful muscular activities is a good strategy is scarce. OBJECTIVE: Therefore, the aim of this study was to determine the acute effects of a single 15-s and 60-s vibrating foam rolling treatment on muscle contractile properties during maximal voluntary isometric contraction (MVIC). METHODS: Twenty healthy and recreationally active subjects participated in this study. During first visit, baseline characteristics were collected, while on the second and third visit they performed a 15-s and a 60-s vibration foam rolling treatment, respectively. Their maximal force (F)max and rate of force development (RFDmax) were assessed using the MVIC of plantarflexors. RESULTS: The RFDmax was negatively affected (p⩽ 0.05) after the 15-s treatment and 60-s treatment, staying reduced even after 10-min of recovery. No significant effects were observed for Fmax. CONCLUSIONS: When implementing vibration foam rolling, either as a pre-workout activity or as a pre-competition treatment, caution should be taken. Short duration treatment should be avoided for activities were RFDmax has a significant impact on performance.

BACKGROUND: Recently there has been a rise in female participation in running yet the female population is under-researched in sport specific research. Locally, many female athletes annually compete in numerous ultra-marathons (> 42 km). OBJECTIVE: This study investigated the importance of Gluteal muscle strength in dynamic pelvic stability of fatigued female endurance road runners. METHODS: Fourteen female endurance runners (age: 38.0 ± 10.12 years, BMI: 21.99 ± 2.37 kg/m2, and VO2max: 40 ± 5.34 ml/min/kg) volunteered for the participation of this study. Through isokinetic testing, muscle strength and fatigability of the Gluteus Maximus, Medius and Minimus was determined. Sign tests compared pelvis stability (unilateral Trendelenburg, Pelvic Bridge test and pelvic stability through a gait analysis) before and after an endurance run on a cambered and flat surface. Participants were divided into two groups based on change in pelvic stability after the fatigue intervention. RESULTS: The unaffected group was moderately younger; lighter in weight and had a lower BMI. Additionally, this group was largely more experienced (p= 0.61, d= 1.341); aerobically fit and ran significantly longer weekly distances (p= 0.002, d= 3.4). There was no statistical difference in isokinetic testing of strength and endurance hip flexion/extension and abduction/adduction between the two groups (p> 0.05). CONCLUSION: In conclusion, the group that was more experienced and ran longer weekly distances showed no change in pelvic stability after an endurance run. However, the group that showed changes in pelvic stability suggests that fatigue could be a contributing factor to pelvic compensation. It is recommended that female endurance runners incorporate strength training to strengthen the Gluteal and Hip Flexor muscle groups to reduce pelvic compensation.

BACKGROUND: Pelvic-drop exercise (PD) is unilateral weight-bearing exercise that is frequently performed in rehabilitation sessions because its easy application can trigger moderate-to-high gluteus medius (Gmed) activity. Hip rotation has been applied to effectively facilitate Gmed activity during exercise. OBJECTIVE: To determine the effects of PD with three different hip rotations on Gmed, tensor fasciae latae (TFL), gluteus maximus (Gmax) activity, and Gmed:TFL activity ratio in patients with Gmed weakness. METHODS: Eighteen subjects with Gmed weakness participated. Subjects performed three different forms of PD with neutral hip, hip internal rotation, and hip external rotation position. Surface electromyography was performed to quantify the activity of Gmed, TFL, and Gmax. RESULTS: PD with hip internal rotation showed significantly greater Gmed activity than with neutral hip and hip external rotation (P= 0.005 and P= 0.007, respectively). TFL also showed significantly greater activity during PD with hip interna rotation than neutral hip (P= 0.002). There were no significant differences in Gmax activity (P= 0.095) and Gmed:TFL activity ratio (P= 0.254) among different forms of PD. CONCLUSIONS: PD with hip internal rotation is recommended to stimulate greater Gmed activity while preserving Gmed:TFL muscle activity ratio.

BACKGROUND: Beetroot juice is an ergogenic aid containing high levels of nitrate and is known to have many physiological benefits. OBJECTIVE: This study aimed to examine the effects of beetroot juice supplementation on the physical capacity and isokinetic muscle function of power athletes. METHODS: Thirteen power athletes were orally administered three different volumes of beetroot juice: placebo (70 ml), low-volume beetroot juice (70 ml), and high-volume beetroot juice (140 ml). The Harvard step test, 20 m sprint, side-step, reaction time, Wingate test, blood lactate analysis, and isokinetic knee and trunk tests were performed to confirm their physical capacity and isokinetic muscle function. Significant differences between the drink groups were determined using repeated-measures ANOVA. RESULTS: There were no significant differences in the Harvard step, side step, whole-body reaction time, anaerobic power, blood lactate concentration, and isokinetic muscular strength in the knee and trunk for all groups. However, the 20 m sprint and isokinetic muscular endurance of the knee extensor were significantly higher with beetroot juice intake. CONCLUSIONS: Our findings suggest that > 70 ml of beetroot juice supplement before performance may be useful as an ergogenic supplement to improve performance-related physical fitness, including speed and muscular endurance, in power athletes.

BACKGROUND: The systematic characteristics of force generation and relaxation have been investigated using a graded isometric task for several target levels and magnitudes in the upper and lower limb. However, whether a relaxation modality affects the accuracy or speed of grading remains unclear. In addition, speed characteristics are still unclear in both force generation and relaxation modalities. OBJECTIVE: To investigate the effect of force adjustment modalities on force generation and relaxation characteristics. METHODS: Participants were instructed to match a target force level as quickly and as accurately as possible under peak and keep adjustment modalities. The force generation task was increased from 10% to 30%, 50%, and 70% of the maximum voluntary force (MVF). The force relaxation task was decreased from 70% to 50%, 30%, and 10% MVF. The recorded force was analyzed. Errors in reproduction were computed in both modalities and target levels of force. RESULTS: The errors of the peak adjustment modality were greater than those of the keep adjustment modality in both tasks. The reaction time was longer with the peak adjustment modality than with the keep adjustment modality in both tasks. CONCLUSION: Speed was affected by the choice of adjustment modality.

BACKGROUND: Analytics, to quantify baseball pitch metrics, take on many forms and are unlike earlier methods to assess performance. OBJECTIVE: Quantify associations of flight kinematic and anthropometric variables on pitch release speed. METHODS: Male college-age pitchers (n= 182) from 2021 Division I games provided data. A 3D radar system collected data. Fixed effects regression OLS models analyzed data for sliders, changeups, curveballs, and fastballs. RESULTS: Spin rate (r= 0.017–0.514, p< 0.05) and vertical break (r= 0.374–0.703, p< 0.05) were positively associated with pitch release speed per pitch type. Release height (r=-0.286–0.051, p<-0.05) and pitch extension (r=-0.176–0.43, p< 0.05) were negatively associated with pitch release speed per pitch type except sliders. Spin axis had a negative association with pitch release speed for fastballs (r=-0.235, p< 0.05) and sliders (r=-0.311, p< 0.05), and a positive association (r= 0.029, p< 0.05) with curveball pitch release speed. Weight only related to pitch release speed for fastballs (r=-0.315, p< 0.05). Height did not impact pitch release speed. CONCLUSIONS: Results refute long-held beliefs of anthropometry’s influence on performance and instead reveal flight kinematics’ impact on baseball pitch release speed.

BACKGROUND: The return to activities and sports after the anterior cruciate ligament (ACL) reconstruction is a critical decision. OBJECTIVE: To verify the most used elements during the isokinetic evaluation for discharge after ACL reconstruction. METHODS: Systematic review (PROSPERO CRD42021224433). Research in the literature: PubMed, Medline, SciELO, Lilacs, CENTRAL, PEDro, Web of Science and Embase, in February 2022. Studies that performed isokinetic evaluation during the discharge period in male patients aged 18 to 59 years after ACL reconstruction. Descriptive synthesis on the most used parameters during isokinetic evaluation as a discharge criteria after ACL reconstruction. RESULT: Twenty-three studies involving 1,792 participants were included. Medium and high quality evidence identified that most isokinetic evaluations targeted only muscle strength after rehabilitation of the ACL (peak moment). CONCLUSION: The most used elements during the isokinetic evaluation were: angular velocity of 60∘/s, 1 set of 5 repetitions, concentric mode and peak moment.