Anna Pisz

Purpose: This study aims to fill a significant gap in sports science research by examining the underexplored effects of asymmetric load training on the deep stabilisation system (DSS), strength, and maximal power in female softball players.Methods: Fourteen participants were divided into two groups: a control group (CON), which exercised with a symmetrically weighted bar, and an experimental group (EXP), which used a bar with asymmetrically distributed weight. The asymmetric load with a distribution of weight that was gradually increased during the 8-week intervention program. The assessment included a 1 repetition maximum (1RM) test for deadlift, flat bench press, front squat, and 4RM tests for single-leg leg press for both legs, along with evaluations of DSS and strength/performance, before and after a resistance training program. A two-way ANOVA was used to compare pre- and post-intervention performance on the DSS and 1RM strength tests.Results: The results showed significant improvements in all 1RM and 4RM tests for both groups in all exercises (p > 0.001), with no significant differences between the groups (p < 0.05). However, a dependent t-test in the EXP group revealed significant improvements in DSS strength/performance from pre- to post-measurements in all tests, with large effect sizes. In contrast, the CON group showed significant improvements only in trunk extension, side plank, and prone tests.Conclusions: These findings indicate that asymmetric training may provide superior benefits in strengthening the DSS, while still achieving comparable gains in maximal strength.

The phenomenon of post-activation performance enhancement plays an unidentified role in movement eccentric speed and individual muscle group responses. Therefore, this study aimed to determine whether the loaded front squat (FSq) speed of the eccentric phase would influence the post-activation performance enhancement effect and whether the FSq would elicit similar performance enhancement of knee flexion, knee extension, hip flexion, and hip extension muscles. Twenty resistance-trained handball players performed the FSq under maximum eccentric-concentric speed and 2-s eccentric speed (only the eccentric phase performed), while pre- and post-front squat countermovement jump, knee, and hip isokinetic flexion/extension performance were tested. The FSq conditioning activity was performed in a single set of three repetitions with either 90% (maximum eccentric-concentric speed) or 120% (2-s eccentric speed) of one repetition maximum, and post-performance was measured 4–12 min after the FSq. Athletes randomly changed the FSq eccentric speed and tested the hip or knee isokinetic flexion/extension strength at 180°/s. ANOVA showed that the rate of force development during the jump increased (Cohen d = 0.59–0.77) with no differences between 2-s eccentric and maximum speed eccentric protocols. Isokinetic strength increased after the 2-s eccentric FSq in hip extension (d = 0.76–0.86), knee flexion (d = 0.74–0.88), and hip flexion (d = 0.82), with no differences in knee extension strength. After maximum eccentric-concentric speed, isokinetic strength increased in hip extension (d = 1.25). In conclusion, the FSq conditioning activity enhances hip extensors' performance more than knee extensors' performance. Different eccentric types of muscle action during a conditioning activity alter the level of local muscle enhancement.

400-m races are based on anaerobic energy metabolism, they induce significant muscle fatigue, muscle fiber damage, and high blood lactate (LA) concentration. Despite extensive research on sprint training, our understanding of the training process that leads to world-class sprint performance is rather limited. This study aimed to determine differences in LA concentration and anaerobic power using jumping tests after an intense glycolytic effort in a group of elite and sub-elite 400-m runners. One hundred thirty male runners were divided into two groups: elite (n = 66, body mass = 73.4 ± 7.8 kg, body height = 182.1 ± 6.2 cm, age = 20.8 ± 4.0 y) running the 400-m dash below 50 s and sub-elite (n = 64, body mass = 72.0 ± 7.1 kg, body height = 182.1 ± 5.2 cm, age = 20.8 ± 4.0 y) with a 400-m personal best above 50 s. The power of the countermovement and the sequential squat jumps was measured in two sets after a warm-up, followed by two intermittent 30-s Wingate tests. LA concentration was measured eight times. It was observed that elite athletes achieved significantly higher power in both types of jumps. The maximum post-exercise LA concentration was significantly lower in the sub-elite group after the 3rd, the 6th, the 9th, and the 20th min after the cessation of two Wingate tests (p < 0.001). The rate of LA accumulation after exercise and the rate of LA utilization did not differ between the groups. It can be concluded that elite and non-elite runners differ in higher LA production but not in LA utilization. Anaerobic power and LA concentration seem to differentiate between 400 elite and sub-elite performance.

The bench press (BP) is a widely used exercise in strength training. Despite numerous studies on muscle activation during BP, little is known about individual muscle frequency changes during the sticking region (SR). This study aimed to evaluate muscle activation during 1 repetition maximum (RM) and 4RM BP in 24 male participants experienced with BP exercise. Electromyography was used to measure muscle activity in various muscles during pre-sticking, sticking, and post-sticking phases, with kinematic data aiding in phase differentiation. Our findings revealed a significant decrease in muscle activation frequency as participants moved from the pre-sticking to the sticking and then to the post-sticking phases (p<0.01). This decline was evident in both 1RM and 4RM conditions, indicating muscle exhaustion that persisted even after the SR. The SR of the BP is the most challenging part of the exercise, resulting in a decrease in muscle frequency during this phase in both 1RM and 4RM repetitions. It indicates exhaustion of the muscles which persisted even in the post-sticking phase, highlighting the challenging nature of the exercise. This study presents insights into muscle activity during the BP, which can help understanding the impact of each exercise phase on muscle frequency.

Introduction: Deep stabilization system (DSS) strength and endurance are crucial for injury prevention and athletic performance. Training surfaces can influence training outcomes; therefore, this study aimed to compare the impact of performing strength trunk exercises on unstable and stable surfaces with conventional trunk exercises. Materials and Methods: DSS and trunk stability were assessed before and after 10 weeks of three different training interventions among twenty elite futsal players. Each intervention included 25 strength training sessions. Pre- and post-tests encompassed various measurements, including diaphragm, trunk flexion, trunk back extension, hip flexion, intraabdominal pressure, side plank, pronation, and supination tests. Results: Conventional exercises showed a significant improvement only in the side plank test. In contrast, unstable and stable surface conditions exhibited notable enhancements in all tests, displaying superior trunk stability compared to conventional exercises. The stable surface condition demonstrated significantly greater improvements in the pronation and supination tests compared to the unstable surface condition. Conclusions: Except for the side plank test, dynamic conventional exercises did not yield substantial improvements in the assessed tests. Deep stabilization system training enhances trunk stability when performed on both unstable and stable surfaces, with unstable surfaces potentially yielding greater improvements in m. transversus stabilization functions.

Knowledge about the acute effects of supramaximal-loaded resistance exercises on muscle mechanical properties is scarce. Therefore, this study aimed to examine changes in dominant limb biceps femoris and vastus lateralis oscillation frequency and stiffness before and after high- and supramaximal-loaded front squats. Nineteen male handball players participated in the experimental session with a barbell front squat 1RM. The first set was performed at 70% of the 1RM for four repetitions, and the second and third sets were performed at 90%1RM in an eccentric–concentric or an eccentric-only manner at 120% of the 1RM for three repetitions. The handheld myometer was used for the measurement of the biceps femoris and vastus lateralis stiffness and the oscillation frequency of the dominant limb 5 min before and at the 5th and 10th min after front squats. A two-way ANOVA neither indicated a statistically significant interaction (p = 0.335; η² = 0.059 and p = 0.103; η² = 0.118), the main effect of a condition (p = 0.124; η² = 0.126 and p = 0.197; η² = 0.091), nor the main effect of the time point (p = 0.314; η² = 0.06 and p = 0.196; η² = 0.089) for vastus lateralis and biceps femoris stiffness. However, there was a statistically significant interaction (F = 3.516; p = 0.04; η² = 0.163) for vastus lateralis oscillation frequency. The post hoc analysis showed a significantly higher vastus lateralis oscillation frequency at POST (p = 0.037; d = 0.29) and POST_10 (p = 0.02; d = 0.29) compared to PRE during the SUPRA condition. Moreover, Friedman’s test indicated statistically significant differences in biceps femoris oscillation frequency (test = 15.482; p = 0.008; Kendall’s W = 0.163). Pairwise comparison showed a significantly lower biceps femoris oscillation frequency in POST (p = 0.042; d = 0.31) and POST_10 (p = 0.015; d = 0.2) during the HIGH condition compared to that in the corresponding time points during the SUPRA condition. The results of this study indicate that the SUPRA front squats, compared to the high-loaded ones, cause a significant increase in biceps femoris and vastus lateralis oscillation frequency.

Krzysztofik, M, Spieszny, M, Trybulski, R, Wilk, M, Pisz, A, Kolinger, D, Filip-Stachnik, A, and Stastny, P. Acute effects of isometric conditioning activity on the viscoelastic properties of muscles and sprint and jumping performance in handball players. J Strength Cond Res 37(7): 1486–1494, 2023—The effects of conditioning activity (CA) on muscle stiffness are currently unknown, suggesting that maximum CA effort can increase or decrease the stiffness of involved muscle groups. Therefore, this study aimed to investigate the effect of maximal isometric half-squats on the viscoelastic properties of muscles and postactivation performance enhancement (PAPE) in sprints and jumps. Twelve handball players underwent a standard warm-up and baseline assessment of muscle stiffness and tone of vastus lateralis and gastrocnemius medialis muscle, followed by 20-m sprint with intermediate measures at 5 and 10 m and countermovement jump. The PAPE was assessed by repeating the tests (at 4th, 8th, and 12th minute post-CA) after a CA protocol consisting of 3 sets of 3-second maximal isometric half-squats (EXP) or a control condition (CTRL) without any CA. The vastus lateralis stiffness in the 4th and 12th minute and muscle tone in the 4th minute post-CA significantly decreased compared with baseline (p = 0.041, ES = 0.57; p = 0.013, ES = 0.52; p = 0.004, ES = 0.81, respectively) in the EXP condition. The 20-m sprint time significantly decreased at all post-CA time points compared with the baseline for the EXP condition (p < 0.033) and the after values in the CTRL condition (p < 0.036). In comparison to baseline, the 10-m sprint time decreased in the eighth minute post-CA (p = 0.021; ES = 0.82) in the EXP condition. Moreover, it was significantly lower at the 8th and 12th minute post-CA (p = 0.038; ES = 0.71 and p = 0.005; ES = 1.26) compared with that time points in the CTRL condition. The maximal isometric half-squats effectively improved sprint performance and significantly decreased vastus lateralis tone and stiffness. These findings offer new insights into the assessment of viscoelastic properties for evaluating the fatigue or potentiation state, which requires further investigation.

This review aimed to summarize the reported effects of unilateral conditioning activity (CA) on unilateral performance, bilateral performance, and the contribution of activated body limb to bilateral performance. A systematic search on MEDLINE, SPORTDiscus, Scopus, and Google Scholar was conducted on February 2022. Twenty-three studies met the inclusion criteria. Throwing, jumping, swimming, change of direction, and isokinetic performance were used as outcome measures to assess the impact of unilateral CAs on inducing post-activation performance enhancement. Eleven studies examined the effectiveness of resistance exercises as a CA, seven investigated plyometric exercises, and five used isokinetic muscle actions as CAs. Notably, only three studies directly compared the effects of bilateral and unilateral CA, and no study reported possible changes in the contribution of each limb during bilateral exercises executed following unilateral CA. Split squats were the most often studied CA (7), and it was shown that multiple sets of high-loaded split squats (85% one-repetition maximum) executed as CA, improve vertical jumping and change of direction after 4 to 8 min of recovery. At the same time, multiple sets of alternate leg bounds performed with ~10% body weight or without any external load result in an improvement of sprint performance, 2 and 8 min later, with the effect being greater when loaded jumps are used. The unilateral CAs such as split squats, alternate leg bounds, and drop jumps can be effectively used to acutely improve a wide variety of athletic tasks, including jumping, sprinting, change of direction, and swimming performance.