Journal of Sports Medicine and Physical Fitness最新文献

Background: Eccentric maximum strength and explosive force production of the hamstrings are crucial for performance in many sports. Tensiomyography (TMG has been shown to be a valuable tool to assess muscle contractility and function. For eccentric force production, neural activation has been proposed to be the predominant influencing factor. Nevertheless, high muscle fiber tension has to be generated. Therefore, this study aims to test the hypothesis that eccentric force production does not correlate with muscle contractility measured by TMG.

Methods: Twenty-three physical active males (26.09±3.25 years) performed maximal eccentric hamstring contractions at 210 °/s on an isokinetic dynamometer. Additionally, TMG measurements were conducted on the biceps femoris. Contraction time, delay time, maximal deformation and contraction velocity were derived and investigated. Spearman correlations between the TMG parameters and maximum torque, rate of torque development (RTD) and time to peak torque were calculated. Furthermore, Kruskal Wallis test was calculated for the TMG parameters between the top and bottom participants according to RTD.

Results: The correlation analysis showed no significant relationships between the TMG parameters and eccentric force production (P>0.05 for all comparisons). For the comparison between the high RTD group and the low RTD group, no significant differences in muscle contractility could be observed.

Conclusions: The results of the present study suggest that muscle contractile properties play a minor role in eccentric force production. Therefore, TMG measures seem not to be suitable to investigate eccentric behavior.

Background: Freediving is a sport that could be defined as both aerobic and anaerobic. Therefore, this study aimed to evaluate the effect of aerobic-anaerobic training on the performance of moderate and elite freedivers.

Methods: The sample of participants included 26 freedivers (9 females) (average age of 26.62±3.34 years, body height of 178.95±9.19 cm, and body mass of 74.64±11.97 kg). The sample of variables included: anthropometric indices, relative maximal oxygen consumption (rVO2max), Diving anaerobic sprint test (DAST), Swimming anaerobic sprint test (SAST), 100-meter crawl sprint test (100 m), maximal dynamic apnea with monofin (DYN), maximal swimming length for 2 minutes (2 min). The study procedure included a 5-month aerobic-anaerobic training intervention. This intervention was conducted during a 4-phase (5-week each) training period.

Results: The results showed that moderate group showed a significant decrease in 100 m (final 83.94±15.68; initial 88.29±16.73; P<0.00), DASTmax (final 10.91±1.46; initial 12.01±1.38; P<0.00), DAST (final 70.29±8.95; initial 79.40±10.25; P<0.00), SASTmax (final 16.81±2.24; initial 18.01±2.69; P<0.00), SAST(final 112.87±19.19; initial 122.65±21.55; P<0.00), and increase in 2 min (final 140.56±21.53; initial 128.68±19.33; P<0.00), and DYN (final 130.48±26.89; initial 91.65; P<0.00). Similarly, the elite group experienced a decrease in 100 m (final 72.18±9.77; initial 75.00±11.36; P=0.02), DASTmax (final 10.14±0.95; initial 10.88±0.99; P=0.03), DAST (final 65.55±6.50; initial 71.24±7.32; P=0.02), SASTmax (final 14.82±1.84; initial 15.76±1.80; P=0.03), and increase in DYN (final 194.94±27.70; initial 161.11±27.70; P<0.00).

Conclusions: The results of this study demonstrate that dynamic apnea, as a main performance factor, had increase in all phases of procedure, with highest increase during anaerobic phases.

Introduction: This systematic review is aimed to evaluate the outcomes of published studies on the topic of fatigue-induced neuromuscular and biomechanical changes after anterior cruciate ligament (ACL) reconstruction.

Evidence acquisition: The identification of studies involved a search across three databases - PubMed, Scopus, and Sportdiscus - until July 2023. The key terms utilized were fatigue, anterior cruciate ligament, biomechanics, electromyography, and landing. Included in the analysis were studies that examined the impact of fatigue on neuromuscular or biomechanical variables in individuals with ACLR, with comparisons drawn to either the contralateral side or healthy controls.

Evidence synthesis: Fourteen studies, involving 396 athletes (245 males, 151 females; mean age 23.43 years) met the inclusion criteria. Among these studies, eleven employed general fatigue protocols, and three used peripheral protocols. The tasks varied across the studies, including single-leg landing tasks, maximum voluntary isometric contraction tests, forward jump, and squat. Despite differing tasks, the findings regarding the impact of fatigue on lower limb kinematics, kinetics, and surface electromyography muscle activation patterns were inconsistent. However, in the majority of cases, the response to fatigue was similar between individuals who had undergone ACL reconstruction (ACLR) and healthy.

Conclusions: The main finding of this systematic review was that fatigue changed things sometimes, however, fatigue did not change biomechanics and activity patterns differently in patients after ACLR vs. controls. General fatigue protocols did not produce enough stimulation to show deference between ACLRs and controls. Future studies should focus on different fatigue protocols (such as sport-specific protocols) and more challenging landing tasks.

Background: The purpose of this study was to determine age group differences in the postural stability of female rhythmic gymnasts, as well as the asymmetries in postural control between them.

Methods: A total of 126 female rhythmic gymnasts (aged 6-12 years) were tested. The rhythmic gymnasts were grouped based on their age between 6-8 years (N.=45; young pioneers), 9-10 years (N.=36; pioneers), and 11-12 years (N.=45; cadets). Postural stability and asymmetry were evaluated by the Y-Balance Test (YBT) with both legs (right and left) in three directions: anterior, posteromedial, and posterolateral and Balance Error Scoring System (BESS). Postural stability was analyzed between age categories using the Kruskal-Wallis Test and Dunn's post-hoc test, and the differences in asymmetry were determined by univariate analysis of variance (ANOVA).

Results: The young pioneers (age 6-8 years) had a greater number of errors in the single-leg foam stance and tandem foam stance than the 9-10-year-old and 11-12-year-old rhythmic gymnasts (P≤0.005). They also had a greater number of errors in BESS Total scores compared to other age categories (young pioneers 18.42±5.63; pioneers 15.08±4.78 and cadets 13.89±5.61; P≤0.005). Results showed significant differences (P≤0.005) between the young pioneers (age 6-8 years) and the cadets (age 11-12 years) in normalized left and right posteromedial reach direction. No significant differences (P≥0.005) in reach asymmetry were observed among age categories.

Conclusions: In conclusion, 6-8-year-old rhythmic gymnasts (young pioneers) should have continuum screening during training and completion development.

Background: This study explored the effects of innovative physical training during COVID-19 periods on college students' health self-efficacy, body image, and subjective well-being.

Methods: Forty-one students were recruited through convenience sampling and assigned to three exercise groups (i.e., aerobic plus resistance exercise [AE+RE], resistance plus aerobic exercise [RE+AE], and traditional dispersed aerobic plus resistance exercise [control]). The intervention sessions for each group were conducted 3 days per week for 30 min per session. The control group participated in a traditional exercise program comprising 5 days per week.

Results: Study results indicated that all three types of physical training programs effectively improved the participants' health self-efficacy (P<0.05). Female students scored significantly higher on health self-efficacy, body image, and subjective well-being than male students (P<0.05). The AE+RE group scored significantly higher on body image and subjective well-being than did the other two groups (RE+AE and control, P<0.05).

Conclusions: This study provides valuable insights that can assist in developing innovative physical education courses at higher education institutions to improve body satisfaction and well-being for the college students.

Background: Highly trained academy soccer practitioners usually implement an aerobic-oriented session followed by a speed-oriented session during the first and second heavy load session of a training week, respectively. This study aimed to investigate if the order of these physical training sessions would influence the external training loads and the subsequent readiness level on match day.

Methods: Twenty-five highly trained academy soccer players (12 U17 and 13 U19) participated in two experimental weeks randomly presented. The AEROBIC-SPEED periodization implemented an aerobic-oriented session on MD-4 and a speed-oriented session on MD-2. The SPEED-AEROBIC periodization did the opposite. During these two sessions, players wore a global positioning system and rated their perceived exertion (RPE). Players were also tested on MD-4 for baseline values (CONTROL) and match-day (TEST). Tests included a counter movement jump (CMJ), a 20-m sprint, the Illinois agility test (IAT), and the Hooper questionnaire.

Results: For the aerobic-oriented session, players reported greater distances during AEROBIC-SPEED periodization than SPEED-AEROBIC in 15-20 km/h (1273.53±328.51 m vs. 1174.84±210.33 m, P<0.05) and 20-25 km/h (658.92±264.41 m vs. 478.17±259.10 m, P<0.01). For the speed-oriented session, players reported greater distances during SPEED-AEROBIC than AEROBIC-SPEED periodization in 20-25 km/h (298.84±120.12 m vs. 223.24±114.86 m, P<0.05) and >25 km/h (110.74±34.65 m vs. 84.96±43.85 m, P<0.05). Tests revealed similar values for CONTROL and TEST between the two experimental weeks for CMJ, 20m, IAT and Hooper.

Conclusions: The physical qualities (both aerobic and speed), when periodized at the beginning of the week (on MD-4) rather than later (MD-2) showed higher external loads without changing the readiness level on MD. The results emphasize the need to periodize the training contents according to the aim of the cycle.

Background: Foot rock-paper-scissors and towel-gathering exercises are widely used for isometric strengthening of intrinsic foot muscles. An initial trial demonstrated that foot rock-paper-scissors and towel-gathering exercises affected skeletal muscles associated with the medial longitudinal arch and toe pressure force, respectively. However, no quantitative reports of interosseous muscle activity after continuous training exist. We aimed to quantitatively assess and compare the impact of foot rock-paper-scissors and towel-gathering exercises on skeletal muscle activity in university athletes over a 3-month period using FDG-PET 3 imaging.

Methods: This randomized controlled clinical trial was conducted in a university hospital with pre- and post-training PET measurements of muscle activity changes. Eight healthy university athletes were subjected to two 3-month-long exercise regimens: foot rock-paper-scissors and towel-gathering. Skeletal muscle activity changes were quantitatively evaluated using FDG-PET imaging. We defined regions of interest across 25 specific muscles and conducted measurements of toe pressure strength and vertical jump height.

Results: The foot rock-paper-scissors exercise initially impacted medial muscles and later intrinsic foot muscles, including lateral longitudinal arch muscles. The towel-gathering exercise improved toe pressure force and vertical jump. Therefore, each exercise targets specific muscle groups differently.

Conclusions: Foot rock-paper-scissors and towel-gathering exercises have distinct effects on skeletal muscle activity. The former primarily enhances medial intrinsic muscles, while the latter improves toe pressure force and vertical jump ability. This highlights the importance of selecting specific exercises for targeted muscle training in athletic and rehabilitation settings. Further research is suggested to extend these findings to broader athletic populations and clinical applications.

Background: Effects comparison of resistance exercises may require equalizing the exercise-induced dose, this is currently done by using methods based on total weight lifted or on sets performed until failure. Dose equalization of resistance training sessions by these methods was analyzed in the present study.

Methods: Twelve trained participants performed five bench-press sessions with a similar relative endpoint determined by the inability to complete a set of 50% of the maximum repetitions number (MNR). Sessions were performed at 50 or 85% of one-repetition maximum (1-RM) with sets until failure or sets prescribing 50% of MNR. The last session was performed with a reduced recovery pause to match the exercise density (total weight lifted/pause duration) of a previous session.

Results: Sessions resulted in different total weight lifted (3158±1592 kg at 85% of 1-RM vs. 5330±1967 at 50%, P<0.001) and number of sets until failure (5.1±1.9 at 85% of 1-RM vs. 2.9±1.1 at 50%, P<0.001). Matching of sessions' density suppressed the differences in the number of sets performed (P=0.50).

Conclusions: Protocols' equalization based on the total weight lifted is likely to result in exercise volumes close to maximums when performed with heavy loads, whereas equalization based on sets to failure could induce a sets number close to the maximum when performed with light loads. Current methods for protocols equalization rely on gross values of exercise volume without considering maximums, that can result in markedly unbalanced efforts and biased results. Prescribing each exercise volume according to its maximum might optimize the training protocols' equalization.

Background: This study aimed to investigate the injury incidence rate among calisthenics athletes and explore the factors associated with injuries, including demographic and athlete characteristics, as well as injury patterns and skill levels.

Methods: We collected data from Dutch calisthenics athletes using an electronic questionnaire administered between February and March 2020. The inclusion criteria required participants to be calisthenics athletes willing to take part and aged over 18 years. Exclusion criteria were applied for individuals residing outside the Netherlands and those who did not comprehend the Dutch or English language.

Results: A total of 401 athletes responded to the survey, of whom 181 met the inclusion criteria. The injury incidence rate over the previous 12 months was 59%. The most frequently injured body parts were the shoulders (32%), wrists (15%), elbows (10%), and back (10%). Several factors were significantly associated with the injury incidence rate, including the duration of participation in calisthenics (6-12 months, 1-2 years, and 2-4 years), doing multiple training sessions per day, utilizing technique training as a warm-up, and possessing an intermediate skill level in power elements.

Conclusions: The findings revealed an injury incidence rate of 59% among calisthenics athletes over the previous 12 months. Calisthenics athletes most often injure their shoulders, wrists, elbows, and back. Athletes who had been training for 6 months to 4 years, did engage in multiple training sessions per day, used technique training as a warm-up, and had an intermediate skill level in power elements were associated with an increased risk of injury.