Rafał Szafraniec

Objectives: The primary aim of this study was to compare the acute effects of two stretching techniques—static stretching (SST) and proprioceptive neuromuscular facilitation (PNF)—on functional outcomes related to postural balance (stabilographic parameters) and ankle range of motion (ROM; active and passive measures). Furthermore, the study aimed to assess the association between changes in balance- and ROM-related parameters. Methods: The study sample consisted of 24 young adults in the age range of 21–24. The SS group (n = 12) mean body height was 174.3 ± 7.8 [cm], body weight 68.0 ± 13.1 [kg], and BMI 22.2 ± 2.8 [kg/m²]. The PNF group’s (n = 12) mean body height was 173.7 ± 7.3 [cm], body weight 68.6 ± 13.5 [kg], and BMI 22.5 ± 3.0 [kg/m²]. The subjects performed static stretching or proprioceptive neuromuscular facilitation stretching involving the tibialis anterior, gastrocnemius, and soleus muscles. Before and immediately after the intervention, the active and passive range of plantar and dorsal flexion of the foot and the stability of the body posture in the anterior–posterior plane were measured based on the analysis of the center of pressure (COP) sway. Results: The results of the mixed model ANOVA (intervention × time) showed no statistically significant effect of the intervention or interaction between intervention and time for ROM and COP measurements. In both cases, a statistically significant time effect was found. After intervention, significant differences were found in COP variability (p = 0.02), COP range (p = 0.03), fractal dimension (p = 0.04), and sample entropy (p = 0.01). Similarly, for range of motion, differences were observed in passive dorsiflexion (p < 0.01), active plantarflexion (p < 0.01), and passive plantarflexion (p = 0.01). Pearson’s correlation analysis did not reveal significant associations between changes in ankle range of motion and COP variables. Conclusions: The results of this study indicate that both static and PNF stretching acutely increase the range of motion in the ankle joint; however, they also lead to a decrease in postural stability under more challenging conditions involving visual or vestibular deprivation. The magnitude of the range of motion changes was not associated with alterations in stabilographic parameters.

Objectives: This study examined whether integrating an isometric exercise program into physical education (PE) lessons influences functional outcomes and cardiovascular risk markers in adolescents beyond the effects of standard PE alone. Methods: Boys aged 14–15 years were randomly assigned to an experimental group (EG, n = 19) or a control group (CG, n = 21). The EG completed a 6-week isometric exercise program integrated into PE lessons, while the CG followed the regular PE curriculum only. The intervention was based on hold isometric muscle actions (HIMA) with progressively increased volume. Anthropometric measures included body height, body mass, and body mass index (BMI). Body composition was assessed using bioelectrical impedance analysis. Functional capacity was evaluated using field-based measures of lower-limb strength and power (isometric mid-thigh pull, standing broad jump, squat jump, and countermovement jump). Systolic and diastolic blood pressure were measured as indicators of cardiovascular health. Results: A mixed model ANOVA showed that no significant group × time interactions were observed for body composition, functional outcomes, or blood pressure (all p > 0.05). Lean body mass increased over time in both groups (p < 0.01). Improvements in isometric mid-thigh pull (p < 0.01) and standing broad jump (p = 0.01) occurred irrespective of group allocation. Blood pressure remained unchanged. Linear regression revealed that biological maturation did not moderate intervention effects; however, more mature participants demonstrated higher absolute strength levels independent of the intervention (p < 0.05). Conclusions: The inclusion of an isometric exercise program within PE lessons did not provide additional benefits for health-related functional outcomes beyond standard PE alone. In its current format, isometric exercise does not appear to add sufficient value to justify its implementation as a stand-alone strategy in school-based PE.

The study aims to evaluate the acute effects of sauna heating and cold immersion on cardiovascular dynamic response in normotensive women. Twenty-eight healthy females underwent a sauna protocol comprising three consecutive 10-min exposures, each separated by a 10-min cooling interval. Blood pressure and heart rate (HR) were measured immediately after leaving the sauna room and in the last minute of the cooling period. Three acute responses after heating in the sauna and three cooling responses had a statistically significant effect on SBP (systolic blood pressure) (p < 0.001), DBP (diastolic blood pressure) (p < 0.001), and HR (p < 0.001). SBP was significantly higher in the first heating session compared to the baseline measurement, while DBP was significantly lower. HR was significantly higher in all three heating sessions compared to the baseline measurement (p < 0.001). Progression analysis revealed a decreasing trend in SBP across heating sessions, whereas no significant trend was observed during cooling sessions. DBP and HR remained stable across heating and cooling cycles. SBP shows high sensitivity to repeated sauna stress, suggesting adaptive cardiovascular effects. However, it is still a preliminary study in young, healthy women, and in the future, more longitudinal studies are needed to identify cardiovascular responses in different age and sex groups, as well as the impact of sauna cycles on individuals with coexisting cardiovascular diseases.

Background/Objectives: The aim of this study was to investigate the acute effect of isometric and plyometric combined activation prior to the endurance performance assessed with the 30-15 Intermittent Fitness Test (30-15 IFT) and cardiovascular parameters. Methods: In this crossover study the data of 14 elite female soccer players aged 22.1 ± 2.9 years were assessed. The conditioning activity (CA) consisted of three sets of five seconds of maximal mid-thigh pull (IMPT), and peak force was measured, and four countermovement jumps were performed. Contact time, jump height, and reactive strength index (RSI) were assessed. Ninety seconds of rest between the sets was performed. Then, 7 min after the CA, the 30-15 IFT was performed. Results: One-way repeated measures (RM) ANOVA showed that performance during the CA did not decrease; what is more, it improved in RSI (p < 0.01). Further, paired samples t-test showed that the performance in the IFT did not change, whereas training impulse (TRIMP) was increased after CA (p = 0.039, ES = 0.61), thus the Bayesian paired test yielded only anecdotal evidence in favor of the alternative hypothesis (BF₁₀ = 1.92; error = 2%). Conclusions: The improvement in CA suggests potentiation rather than fatigue. However, the unchanged performance alongside a modest TRIMP increase should be interpreted with caution, as TRIMP alone provides a limited assessment of physiological cost. Therefore, while the applied protocol did not enhance endurance performance, further research using multiple physiological markers is needed to clarify its impact on internal load and overall efficacy.

(1) Background: The growing prevalence of obesity, diabetes, hypertension, and declining physical fitness among children and adolescents due to sedentary lifestyles has increased attention toward preventive intervention to tackle this issue. This study investigated the age-related effects of high-intensity functional training (HIFT), based on bodyweight resistance exercises conducted during physical education lessons, on muscle mass and strength improvement. (2) Methods: Adolescent males (n = 116) were allocated to four HIFT experimental groups (EGs) and four standard physical education program control groups (CGs) according to age (15, 16, 17, and 18 years [y]). The changes in muscle mass (absolute and relative to height [SMI]), hand–grip strength (HGS), sit-ups (SUs), and standing broad jump (SBJ) were analyzed using two-way analysis of variance (ANOVA) with Bonferroni tests. (3) Results: HIFT significantly increased muscle mass and scores in all strength tests (p < 0.01), while chronological age was significant for HGS (p < 0.01). Interactions between HIFT and chronological age categories were observed for HGS (p = 0.01) and SBJ (p < 0.03). Detailed post hoc tests revealed improvement in muscle mass across all chronological age categories for both approaches (p < 0.05). The 18y-EG group improved HGS over their control peers (p < 0.01), the EG groups significantly improved their SU results (p < 0.01), and SBJ improved in the 15y-EG and 18y-EG groups compared to their control (p < 0.01). (4) Conclusions: This research highlights the effectiveness of a school-based HIFT program in promoting muscle mass gains and enhancing muscle strength among adolescents. The findings offer valuable insights for implementing bodyweight exercises during physical education classes.

Background: The effects of low-intensity resistance training on health and muscular performance have been widely reported, but its effects on motor skills such as balance and force matching have been overlooked. Hence, the purpose of this study was to determine the effects of low-intensity resistance training on a force-matching task and balance. Methods: The subjects from the intervention group (EXP; n = 20) participated in a 12-week low-intensity resistance training program. The measurements of balance and force-matching ability were conducted before and after the intervention. To determine the accuracy and steadiness (variability) in the force matching task, we calculated the values of three errors: (1) absolute error (AE), (2) constant error (CE), and (3) variable error (VE). Results: In the force-matching task performed after the training, the values of two errors decreased: (1) AE (right leg, p = 0.0008; left leg, p = 0.0008), and (2) CE (right leg, p = 0.0064; left leg, p = 0.0440). Resistance training did not significantly affect VE and the parameters characterizing COP sway in the balance test. Conclusions: The 12-week low-intensity resistance training improved the accuracy of the force-matching task but did not change postural stability or postural strategies.

The study aimed to investigate the impact of a 12-week strength training program on force accuracy and steadiness changes in lower limbs in young healthy men. Twenty subjects with a dominant right lower limb were included. They performed a force matching task both pre and post strength training program. The ability to reproduce force was determined by calculating three errors: absolute error (AE), constant error (CE), and variable error (VE). After intervention AE and VE improved in both legs indicating higher improvement in the dominant leg (p = 0.032 for AE and p = 0.005 for VE). However, CE improved only in the dominant leg (p = 0.001). We conclude that strength training improved the accuracy and consistency of force in a force reproduction task. This improvement was more evident in the dominant lower limb. Most likely, the inter-limb asymmetry in changes of force application ability caused by strength training is due to the different mechanisms responsible for the control of voluntary movements in the dominant and non-dominant lower limb.

Our primary objective was to investigate the effects of short-term core stability training on dynamic balance and trunk muscle endurance in novice weightlifters learning the technique of the Olympic lifts. Our secondary objective was to compare dynamic balance and trunk muscle endurance between novice and experienced weightlifters. Thirty novice (NOV) and five experienced (EXP) weightlifters participated in the study. Mediolateral (ML) and anteroposterior (AP) dynamic balance and trunk muscle endurance testing were performed a week before (Pre) and after (Post) a 4-week core stability training program. In the NOV group, there was an improvement of both dynamic balance (ML and AP, p = 0.0002) and trunk muscle endurance (p = 0.0002). In the EXP group, there was no significant difference between Pre and Post testing conditions, except an increase in muscle endurance in the right-side plank (p = 0.0486). Analysis of the results showed that experienced lifters were characterized by more effective dynamic balance and greater core muscle endurance than their novice peers, not only before the training program but after its completion as well. In conclusion, the applied short-term core stability training improved dynamic balance and trunk muscle endurance in novice weightlifters learning the Olympic lifts. Such an exercise program can be incorporated into a training regime of novice weightlifters to prepare them for technically difficult tasks of the Olympic snatch and clean and jerk.

The present study aimed to evaluate the effects of a 6-week high-velocity strength training (HVST) intervention on movement velocity and strength endurance in experienced powerlifters with cerebral palsy (CP). Eleven experienced powerlifters with CP and seven from a control group (CON), were subjected to 6-week HVST. An assessment of movement velocity and strength endurance was conducted one week before (T1) and one week after (T2) the 6-week training intervention. During testing, athletes performed a maximum number of bench press repetitions possible within 5 sets of 15 s each, with 1-min passive rest intervals in-between. The indicator of movement velocity was the weight pressed in the first 5 s (5sW) in all performed sets. Strength endurance was described by the total weight (TW) pressed during the test. 5sW in T2 was significantly higher as compared with T1 in the CP group only (T1 928.9 ± 342.9 kg vs. T2 1007.3 ± 324.6 kg; p = 0.016). TW in T2 was significantly higher as compared with T1, both in the CP group (T1 2550.5 ± 843.9 kg vs. T2 2809.8 ± 981.3 kg; p < 0.001) and in the CON group (T1 2300.7 ± 845.1 kg vs. T2 2468.9 ± 890.1 kg; p = 0.049). A 6-week program of HVST increased movement velocity in resistance trained CP athletes. The gains of strength endurance were observed in both groups.

Background: Balance control has been shown to play a fundamental role both in everyday life and many athletic activities. An important component of balance control is the somatosensory information gained from muscle spindles and Golgi tendon organs. The changes in the muscle-tendon unit stiffness could alter the ability to detect and respond promptly to changes of an unstable environment. One of the procedures affecting muscle stiffness is stretching, and contract-relax PNF stretching (CRS) is considered as one of the safest and most effective techniques. So far, there are no studies on the impact of CRS of hip adductor and abductor muscles on body balance. These muscle groups are responsible for maintaining mediolateral balance which is of particular interest, since it is more affected by ageing and disease and since its deterioration has been associated with an increased risk of falling. In light of the above, the aim of the present study was to investigate the effects of a single dose of contract-relax proprioceptive neuromuscular facilitation stretching of hip adductors and abductors on mediolateral dynamic balance. Methods: The study involved 45 healthy individuals (age 19–23 years) assigned to the intervention group (IG) or the control group (CG). Balance testing was carried out before (Pre) and immediately after CRS in the intervention group or after 5-minute rest in the control group (Post). There were performed three repetitions of the CRS targeting the adductor and abductor muscles of the hip. Results: Statistically significant differences between Pre and Post condition were observed only in the intervention group. The values of all measured variables defining the body’s dynamic balance were significantly lower immediately after the applied CRS, which indicates an improved body balance: Global Index (p = 0.0001), total area of sway (p = 0.0001), external area of sway (p = 0.00004), external time (p = 0.0004) and reaction time (p = 0.0003). Conclusions: A single dose of contract-relax proprioceptive neuromuscular facilitation stretching of the hip adductor and abductor muscles improved mediolateral dynamic balance.