1,066 publications found
Sort by
The relationship between jumping, acceleration, change of direction, and relative strength for deadlift and back squat

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.

Comparison of tensiomyographic contractile properties of the knee muscles between endurance and power athletes

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.

Acute effects of vibration foam rolling on the explosive strength properties of the plantarflexors during maximal isometric contraction

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.

The importance of gluteal muscle strength in dynamic pelvic stability of fatigued female endurance road runners

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.

Effect of different pelvic-drop exercises on hip muscles activity in patients with gluteus medius weakness

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.

High or low volume beetroot juice supplementation might positively affect physical capacity and isokinetic muscle function in power athletes

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.