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Maximal strength is considered a fundamental aspect of athletic performance across a wide range of sports and is also needed for a range of activities of daily life. Yet, compared to males there are fewer publications examining females, with most showing similar coefficients of correlation between dynamic strength and different athletic performances. In both, males and females, results are biased by mostly small sample sizes (sample bias) leading to a fluctuation around the true correlation coefficient of the entire population. This crosssectional analysis involving 1544 participants employed multivariate and correlative analyses to clarify the importance of maximum strength in the parallel back squats on the jump performance controlling for variables such as type of sport, sex, age, and performance level. The analysis revealed two principal components that reflect distinct types of variability within the dataset: the first, primarily associated with performance capabilities, accounts for 58.45% of the variance, while the second, emphasizing demographic differences, accounts for a considerably lower variance of 25.08%. The correlation analyses in this study identified maximal strength as a significant factor influencing jumping performance, accounting for 48-53% of the variance in jump height. The analysis presents a saturation curve, with potential diminishing returns at higher strength levels. Age and sex had little to no effect on overall correlation coefficients. The overall correlation coefficients and the analyses for the subgroups (by sport and performance level) can differ considerably, which can be explained (mathematically) by the artificial formation of clusters, homogeneous subject groups, or small sample sizes.

The present study investigated the activation of gluteal, thigh, and lower back muscles in different squat variations. Ten male competitive bodybuilders perform back-squat at full (full-BS) or parallel (parallel-BS) depth, using large feet-stance (sumo-BS), and enhancing the feet external rotation (external-rotated-sumo-BS) and front-squat (FS) at 80% 1-RM. The normalized surface electromyographic root-mean-square (sEMG RMS) amplitude of gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, vastus medialis, adductor longus, longissimus, and iliocostalis was recorded during both the ascending and descending phase of each exercise. During the descending phase, greater sEMG RMS amplitude of gluteus maximus and gluteus medius was found in FS vs. all other exercises (p < 0.05). Additionally, FS elicited iliocostalis more than all other exercises. During the ascending phase, both sumo-BS and external-rotated-sumo-BS showed greater vastus lateralis and adductor longus activation compared to all other exercises (p < 0.05). Moreover, rectus femoris activation was greater in FS compared to full-BS (p < 0.05). No between-exercise difference was found in vastus medialis and longissimus showed no between-exercise difference. FS needs more backward stabilization during the descending phase. Larger feet-stance increases thigh muscles activity, possibly because of their longer length. These findings show how bodybuilders uniquely recruit muscles when performing different squat variations.

The 'strength-endurance continuum' is a key concept in strength training (ST). Although cardiopulmonary responses have seldom been reported in conjunction with ST, this repeated-measurement study examined acute blood pressure and haemodynamic responses continuously depending on the number of repetitions but without changing the intensity. Fifteen healthy male participants (21.6 (2.0) years; mean (SD)) performed an incremental exercise test and a 3-repetition maximum test (3-RM) on a Smith machine. They were then randomly assigned to three ST sessions involving 10, 20 and 30 repetitions at 50% of their 3-RM. Blood pressure (vascular unloading technique) and cardiopulmonary responses (spirometry and impedance cardiography) were continuously monitored. Heart rate (121 (10) vs. 139 (22) vs. 153 (13) bpm, P = 0.001, respectively), cardiac output (10.4 (1.9) vs. 13.6 (3.8) vs. 14.6 (3.1) L/min, P = 0.001, respectively) and diastolic blood pressure (113 (8) vs. 116 (21) vs. 135 (22) mmHg, P = 0.001, respectively) increased in the training sessions with higher repetitions. Stroke volume, systolic blood pressure and end-diastolic volume indicated no change in peak values between training sessions. Total peripheral resistance (13.6 (2.8) vs. 11.3 (3.6) vs. 11.2 (3.1) mmHg min/L, P = 0.002, respectively) was significantly lower with 20 and 30 repetitions, while oxygen uptake ( V ̇ O 2 ${\\dot V_{{{\\mathrm{O}}_{\\mathrm{2}}}$ : 15.5 (1.9) vs. 20.5 (4.1) vs. 20.6 (4.4) mL/min/kg, P = 0.001, respectively) was significantly higher. ST of moderate intensity with an exhausting number (>20) of repetitions induces strong haemodynamic responses, especially high cardiac afterload and a compensatory heart rate acceleration, which may also create a strong stimulus for cardiopulmonary adaptation.The 'strength-endurance continuum' is a key concept in strength training (ST). Although cardiopulmonary responses have seldom been reported in conjunction with ST, this repeated-measurement study examined acute blood pressure and haemodynamic responses continuously depending on the number of repetitions but without changing the intensity. Fifteen healthy male participants (21.6 (2.0) years; mean (SD)) performed an incremental exercise test and a 3-repetition maximum test (3-RM) on a Smith machine. They were then randomly assigned to three ST sessions involving 10, 20 and 30 repetitions at 50% of their 3-RM. Blood pressure (vascular unloading technique) and cardiopulmonary responses (spirometry and impedance cardiography) were continuously monitored. Heart rate (121 (10) vs. 139 (22) vs. 153 (13) bpm, P = 0.001, respectively), cardiac output (10.4 (1.9) vs. 13.6 (3.8) vs. 14.6 (3.1) L/min, P = 0.001, respectively) and diastolic blood pressure (113 (8) vs. 116 (21) vs. 135 (22) mmHg, P = 0.001, respectively) increased in the training sessions with higher repetitions. Stroke volume, systolic blood pressure and end-diastolic volume indicated no change in peak values between training sessions. Total peripheral resistance (13.6 (2.8) vs. 11.3 (3.6) vs. 11.2 (3.1) mmHg min/L, P = 0.002, respectively) was significantly lower with 20 and 30 repetitions, while oxygen uptake ( V ̇ O 2 ${\\dot V_{{{\\mathrm{O}}_{\\mathrm{2}}}$ : 15.5 (1.9) vs. 20.5 (4.1) vs. 20.6 (4.4) mL/min/kg, P = 0.001, respectively) was significantly higher. ST of moderate intensity with an exhausting number (>20) of repetitions induces strong haemodynamic responses, especially high cardiac afterload and a compensatory heart rate acceleration, which may also create a strong stimulus for cardiopulmonary adaptation.

(1) Purpose: This study aimed to explore the time duration of post-activation performance enhancement (PAPE) in elite male sprinters with different strength levels. (2) Methods: Thirteen elite male sprinters were divided into a strong group (relative strength: 1RM squat normalized by body mass of ≥2.5; n = 6) and a weak group (relative strength of <2.5; n = 7). All sprinters performed one static squat jump (SSJ) at baseline and 15 s, 3 min, 6 min, 9 min, and 12 min following an exercise protocol including three reps of a 90% 1RM back squat. Two force plates were used to determine the vertical jump height, the impulse output, and the power output for all SSJs. (3) Results: Significant improvements in vertical jump height and peak impulse were observed (p < 0.05) at 3, 6, and 9 min, without significant between-group differences. The peak power had a significant increase in 3 min (p < 0.01) and 6 min (p < 0.05), with also no significant difference between-group differences. Moreover, the stronger subjects induced a greater PAPE effect than the weaker counterparts at 3, 6, and 9 min after the intervention. The maximal benefit following the intervention occurred at 6 min and 3 min after the intervention in the stronger and weaker subjects, respectively. (4) Conclusions: The findings indicated that three reps of a 90% 1RM back squat augmented the subsequent explosive movement (SSJ) for 3–9 min in elite male sprinters, especially in stronger sprinters.

The barbell squat is a multijoint exercise often employed by athletes and fitness enthusiasts due to its beneficial effects on functional and morphological neuromuscular adaptations. This study compared the effects of squat variations on lower limb muscle strength and hypertrophy adaptations. Twenty‐four recreationally trained females were assigned to a 12‐week front squat (FS; n = 12) or back squat (BS; n = 12) resistance training protocol (twice per week). Maximum dynamic strength (1‐RM) on the 45° leg press, a nonspecific strength test, and muscle thickness of the proximal, middle, and distal portions of the lateral thigh were assessed at baseline and post‐training. A significant time versus group interaction was observed for 1‐RM values (F(1,22) = 10.53; p = 0.0004), indicating that BS training elicits greater improvements in muscle strength compared with FS training (p = 0.048). No time versus group interactions were found for muscle thickness (F(1,22) = 0.103; p = 0.752); however, there was a significant main effect of time for the proximal (F(1,22) = 7.794; p = 0.011), middle (F(1,22) = 7.091; p = 0.014), and distal portions (F(1,22) = 7.220; p = 0.013) of the lateral thigh. There were no between‐group differences for any muscle thickness portion (proximal: p = 0.971; middle: p = 0.844; and distal: p = 0.510). Our findings suggest that BS elicits greater improvements in lower limb muscle strength on the 45° leg press than FS, but hypertrophic adaptations are similar regardless of variations during the squat exercise. Highlights Back squat training elicited greater strength‐related improvements in a nonspecific strength test than front squat training. Hypertrophic adaptations of the lateral thigh are similar between both squat variations. Both squat variations elicited similar growth at proximal, middle, and distal regions of the lateral thigh.

Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.

This study aimed to investigate the effect of the load and bar position on trunk and lower extremity muscle activity during squat exercise. High bar back squats (HBBS) and low bar back squats (LBBS) were performed in random order at 50%, 60%, and 70% loads of one repetition maximum by 28 experienced healthy adult men who had been performing squats for at least one year. Before the experiment, the maximal voluntary contraction of the vastus medialis, vastus lateralis, rectus femoris, biceps femoris, rectus abdominis, transverse abdominis, external oblique, and erector spinae muscles was measured by means of surface electromyography. In addition, eccentric and concentric exercises were performed for 3 s each to measure the muscle activity. There was a significant difference in muscle activity according to the load for all muscles in the eccentric and concentric phases (p < 0.05), indicating that muscle activity increased as the load increased. In addition, in the comparison between HBBS and LBBS, significant differences were shown in all lower extremity muscles and all trunk muscles except for the external oblique in the concentric phase according to the bar position (p < 0.05). HBBS showed a higher muscle activity of the lower extremity in the eccentric and concentric phases than in LBBS, while LBBS showed a higher muscle activity of the trunk muscle in the eccentric and concentric phases than in HBBS (p < 0.05). HBBS requires more force in the lower extremity than LBBS and is particularly advantageous in strengthening the muscular strength of the quadriceps. In contrast, LBBS requires more muscle activity in the trunk than HBBS and is more effective in carrying heavier loads because of the advantage of body stability. This study suggests that rehabilitation experts apply the bar position and load as important variables affecting the intensity and method of training for target muscle strengthening of the lower extremities and trunk.

The aim of this study was to determine the optimal velocity loss (VL) threshold that maximises the post activation potentiation (PAP) stimulus for achieving larger and more consistent performance gains in track and field athletes. Twenty-two athletes from athletics participated in four back squat PAP tests with four different VL threshold (5%, 10%, 15% and 20% VL) at an intensity of 85%1RM. Countermovement jump (CMJ) height, power, and momentum were assessed before, and 10 s, 4, 8, 12, 16 minutes after the PAP condition. Repetitions of the squat in all the PAP conditions were also recorded. Only the 5% VL condition produced significant improvements in height (ES = 0.73, P = 0.038), peak power output (ES = 0.73, P = 0.038) and momentum (ES = 0.72, P = 0.041) of CMJ, and these changes appeared 8 minutes after the condition. The total number of repetitions during the 5% VL condition was significantly lower than that observed in the 15% (P = 0.003) and 20% VL (P < 0.001) trials. The results from this study indicate that 5%VL during the 2 sets preconditioning squat at 85%1RM was optimal for eliciting PAP in a CMJ exercise, and resulted in significant increases at the 8-min recovery period. The same squat condition also had the least number of repetitions. However, considering the efficiency in practice, athletes can also choose the rest time of 4-min, which can also achieve similar results.

Dynamic knee valgus (DKV) as an incorrect movement pattern is recognized as a risk factor for lower limb injuries. Therefore, it is important to find the reasons behind this movement to select effective preventive procedures. There is a limited number of publications focusing on specific tasks, separating the double-leg from the single-leg tasks. Test patterns commonly used for DKV assessment, such as single-leg squat (SLS) or single leg landings (SLL), may show different results. The current review presents the modifiable factors of knee valgus in squat and landing single-leg tests in healthy people, as well as exercise training options. The authors used the available literature from PubMed, Scopus, PEDro and clinicaltrials.gov databases, and reviewed physiotherapy journals and books. For the purpose of the review, studies were searched for using 2D or 3D motion analysis methods only in the SLL and SLS tasks among healthy active people. Strengthening and activating gluteal muscles, improving trunk lateral flexion strength, increasing ROM dorsiflexion ankle and midfoot mobility should be taken into account when planning training programs aimed at reducing DKV occurring in SLS. In addition, knee valgus during SLL may occur due to decreased hip abductors, extensors, external rotators strength and higher midfoot mobility. Evidence from several studies supports the addition of biofeedback training exercises to reduce the angles of DKV.

Many sports require rapid acceleration and deceleration, particularly when changing direction. These movements require a large impulse, highlighting the importance of rates of force development (RFDs). However, the relationships between acceleration and deceleration performance and concentric and eccentric RFDs have remained uncertain. This study evaluated the correlation between RFDs in different muscle contraction types and acceleration and deceleration performances. This study included 28 healthy subjects (13 males and 15 females; age: 21 ± 2 years; height: 1.66 ± 0.09 m; body mass: 65 ± 10 kg). Concentric, eccentric, and isometric RFDs were evaluated by having the subjects perform squat jumps, countermovement jumps, and isometric squats, respectively. Acceleration and deceleration performances were measured using a 10-yard (9.14 m) sprint and change of direction deficit (COD ; calculated by subtracting the linear sprint time from the total time of the pro-agility test), respectively. Correlation analyses were performed to determine the relationship between the RFDs and the 10-yard sprint time and COD . The Pearson product-moment correlation coefficient (r) was used for normally distributed dependent variable combinations, whereas the Spearman rank correlation coefficient (r(s)) was applied when at least one variable was not normally distributed. A faster 10-yard sprint time was only correlated with greater concentric RFD (r(s) = -0.41, = 0.03, 95% CI [-0.69 to -0.03]), whereas a smaller COD was only correlated with greater eccentric RFD (r(s) = -0.44, = 0.02, 95% CI [-0.71 to -0.07]). The isometric RFD showed no correlation with any performance parameters. A faster 10-yard sprint time was only correlated with a greater concentric RFD, whereas a smaller COD was only correlated with a greater eccentric RFD. Overall, these results provide insights into the association between the acceleration and deceleration performance and RFDs according to muscle contraction type, which could help in the creation of effective training methods for improving acceleration and deceleration performance.