J. Funct. Morphol. Kinesiol., Volume 6, Issue 4 (December 2021) – 24 articles

Heart rate variability (HRV) may be useful for prescribing high-intensity functional training (HIFT) exercise programs. This study aimed to compare effects of HRV-guided and predetermined HIFT on cardiovascular function, body composition, and performance. Methods: Recreationally-active adults (n = 55) were randomly assigned to predetermined HIFT (n = 29, age = 24.1 ± 4.1 years) or HRV-guided HIFT (n = 26, age = 23.7 ± 4.5) groups. Both groups completed 11 weeks of daily HRV recordings, 6 weeks of HIFT (5 d·week-1), and pre- and post-test body composition and fitness assessments. Meaningful changes in resting HRV were used to modulate (i.e., reduce) HRV-guided participants’ exercise intensity. Linear mixed models were used with Bonferroni post hoc adjustment for analysis. Results: All participants significantly improved resting heart rate, lean mass, fat mass, strength, and work capacity. However, no significant between-groups differences were observed for cardiovascular function, body composition, or fitness changes. The HRV-guided group spent significantly fewer training days at high intensity (mean difference = −13.56 ± 0.83 days; p < 0.001). Conclusion: HRV-guided HIFT produced similar improvements in cardiovascular function, body composition, and fitness as predetermined HIFT, despite fewer days at high intensity. HRV shows promise for prescribing individualized exercise intensity during HIFT. Full article

Aerobic training is known to influence cognitive processes, such as memory and learning, both in animal models and in humans. Particularly, in vitro and in vivo studies have shown that aerobic exercise can increase neurogenesis in the dentate gyrus, improve hippocampal long-term potentiation (LTP), and reduce age-related decline in mnemonic function. However, the underlying mechanisms are not yet fully understood. Based on this evidence, the aim of our study was to verify whether the application of two aerobic training protocols, different in terms of speed and speed variation, could modulate synaptic plasticity in a young murine model. Therefore, we assessed the presence of any functional changes by extracellular recordings in vitro in mouse hippocampal slices and structural alterations by transmission electron microscopy (TEM). Our results showed that an aerobic training protocol, well designed in terms of speed and speed variation, significantly contributes to improving synaptic plasticity and hippocampal ultrastructure, optimizing its benefits in the brain. Future studies will aim to clarify the underlying biological mechanisms involved in the modulation of synaptic plasticity induced by aerobic training. Full article

In goal-directed movements, effective open-loop control reduces the need for feedback-based corrective submovements. The purpose of this study was to determine the influence of hand preference and aging on submovements during single- and two-joint pointing movements. A total of 12 young and 12 older right-handed participants performed pointing movements that involved either elbow extension or a combination of elbow extension and horizontal shoulder flexion with their right and left arms to a target. Kinematics were used to separate the movements into their primary and secondary submovements. The older adults exhibited slower movements, used secondary submovements more often, and produced relatively shorter primary submovements. However, there were no interlimb differences for either age group or for the single- and two-joint movements. These findings indicate that open-loop control is similar between arms but compromised in older compared to younger adults. Full article

Background: Clear recommendations about the optimal treatment of traumatic tarsal navicular fractures are still very debated in the literature, and this is due to several factors: navicular fractures are rare and often misdiagnosed injuries, they are frequently associated with other fractures or a dislocation of the midfoot, and the current knowledge is based on few papers mainly considering a limited number of cases and dealing with different therapeutic approaches. The treatment of navicular body fractures is controversial and burdened by a high incidence of complications; in particular, Sangeorzan type III comminuted fractures represent a real challenge for the orthopedic surgeon. An accurate preoperative planning, a scrupulous surgical technique aimed at restoring volume and bony anatomy, and the use of low-profile angular-stability plates can lead to optimal clinical and functional results, decreasing the chances of arthritic evolution of mid-foot joints. Full article

The aim of our study was to assess the effect of 8 weeks of pulmonary rehabilitation (PR) in patients with pulmonary embolism (PE) during unsupervised PR (unSPR_group) versus supervised PR (SPR_group) on cardiopulmonary exercise testing (CPET) parameters, sleep quality, quality of life and cardiac biomarkers (NT-pro-BNP). Fourteen patients with PE (unSPR_group, n = 7, vs. SPR_group, n = 7) were included in our study (age, 50.7 ± 15.1 years; BMI, 30.0 ± 3.3 kg/m²). We recorded anthropometric characteristics and questionnaires (Quality of life (SF-36) and Pittsburg sleep quality index (PSQI)), we performed blood sampling for NT-pro-BNP measurement and underwent CPET until exhausting before and after the PR program. All patients were subjected to transthoracic echocardiography prior to PR. The SPR_group differed in mean arterial pressure at rest before and after the PR program (87.6 ± 3.3 vs. 95.0 ± 5.5, respectively, p = 0.010). Patients showed increased levels of leg fatigue (rated after CPET) before and after PR (p = 0.043 for SPR_group, p = 0.047 for unSPR_group) while the two groups differed between each other (p = 0.006 for post PR score). Both groups showed increased levels in SF-36 scores (general health; p = 0.032 for SPR_group, p = 0.010 for unSPR_group; physical health; p = 0.009 for SPR_group, p = 0.022 for unSPR_group) and reduced levels in PSQI (cannot get to sleep within 30-min; p = 0.046 for SPR_group, p = 0.007 for unSPR_group; keep up enough enthusiasm to get things done; p = 0.005 for SPR_group, p = 0.010 for unSPR_group) following the PR program. The ΝT-pro-BNP was not significantly different before and after PR or between groups. PR may present a safe intervention in patients with PE. The PR results are similar in SPR_group and unSPR_group. Full article

Implant-associated infections still represent one of the main problems in treatment of open fracture. The role of systemic antibiotic prophylaxis is now agreed and accepted; however, recent literature seems to underline the importance of local antibiotic therapy at the fracture site, and antibiotic nails have been shown to play a role in the treatment of open fractures in terms of fracture healing and lower risk of infection. We retrospectively analyzed our results, from January 2016 to March 2020, with the use of coated nails in the treatment of open tibial fractures, evaluating the rates of infection and fracture healing as primary outcomes and the rate of reoperations, time from trauma to nailing and hospital stay as secondary outcomes. Thirty-eight patients treated with coated nail (ETN Protect^TM, Synthes) were included in the study. Minimum follow-up was of 18 months. Thirty-four of 38 patients achieved bone union and 2 patients underwent septic non-union. In our series, no systemic toxicity or local hypersensitivity to antibiotics were recorded. From this study, use of antibiotic-coated nails appears to be a valid and safe option for treatment of open tibial fractures and prevention of implant-related infections, particularly in tibial fractures with severe soft tissue exposure and impairment. Full article

The goals of this narrative review are to provide a brief overview of the muscle and tendon adaptations to eccentric resistance exercise and address the applications of this form of training to aid rehabilitative interventions and enhance sports performance. This work is centered on the author contributions to the Special Issue entitled “Eccentric Exercise: Adaptations and Applications for Health and Performance”. The major themes from the contributing authors include the need to place greater attention on eccentric exercise mode selection based on training goals and individual fitness level, optimal approaches to implementing eccentric resistance exercise for therapeutic purposes, factors that affect the use of eccentric exercise across the lifespan, and general recommendations to integrate eccentric exercise in athletic training regimens. The authors propose that movement velocity and the absorption or recovery of kinetic energy are critical components of eccentric exercise programming. Regarding the therapeutic use of eccentric resistance training, patient-level factors regarding condition severity, fitness level, and stage of rehabilitation should govern the plan of care. In athletic populations, use of eccentric exercise may improve movement competency and promote improved safety and performance of sport-specific tasks. Eccentric resistance training is a viable option for youth, young adults, and older adults when the exercise prescription appropriately addresses program goals, exercise tolerability, and compliance. Despite the benefits of eccentric exercise, several key questions remain unanswered regarding its application underscoring the need for further investigation. Full article

It has been reported that the variability of resting blood lactate concentration (BLa) is related to metabolic capacity. However, it is unclear whether the resting BLa of athletes can be utilized as a metabolic biomarker. This longitudinal case study tested the hypothesis that resting BLa levels in the morning fluctuate with a 1-year training cycle. The subject was an adult male sprinter, and BLa and blood glucose at the time of waking were measured every day for 1 year. The training cycles were divided into five phases: 1. Basic training: high-intensity and high-volume load; 2. Condition and speed training: high-intensity and low-volume load; 3. Competition training I: track race and high-intensity load; 4. Conditioning for injury; 5. Competition training II. The mean BLa levels in the basic training (1.10 ± 0.32 mmol/L and competition training I (1.06 ± 0.28 mmol/L) phases were significantly lower than in the condition and speed training (1.26 ± 0.40 mmol/L) and conditioning injury (1.37 ± 0.34 mmol/L) phases. The clarified training cycle dependence of resting BLa is suggested to be related to the ability to utilize lactate as an energy substrate with fluctuations in oxidative metabolic capacity. This case report supports the tentative hypothesis that resting BLa may be a biomarker index linked to the metabolic capacity according to the training cycle. Full article

The present study examined how prevalent methods for determining maximal voluntary contraction (MVC) impact the experimentally derived functions of graded force-force variability. Thirty-two young healthy subjects performed continuous isometric force tracking (20 s trials) at 10 target percentages (5–95% MVC) normalized to a conventional discrete-point (n = 16), or sustained (n = 16) MVC calculation. Distinct rates and magnitudes of change were observed for absolute variability (standard deviation (SD), root mean squared error (RMSE)), tracking error (RMSE, constant error (CE)), and complexity (detrended fluctuation analysis (DFA)) (all p < 0.05) of graded force fluctuations between the MVC groups. Differential performance strategies were observed beyond ~65% MVC, with the discrete-point group minimizing their SD at force values below that of the criterion target (higher CE/RMSE). Moreover, the sustained group’s capacity to minimize SD/RMSE/CE corresponded to a more complex structure in their force fluctuations. These findings reveal that the time component of MVC estimation has a direct influence on the corrective strategies supporting near-maximal manual force control. While discrete MVC protocols predominate in the study of manual strength/endurance/precision, a 1:1 MVC-task mapping appears more to be ecologically valid if visuo-motor precision outcomes are of central importance. Full article

L-carnitine supplementation improves body strength, sports endurance and exercise capacity, as well as delaying the onset of fatigue. The aim of this study was to identify the correct dosage of supplementation to obtain improvements in physical performance and evaluate the changes related to L-carnitine supplementation in specific metabolic parameters, such as serum lactate, VO₂, serum total and free carnitine at rest and after physical activities, in healthy subjects. The search was conducted on PubMed, EMBASE, Cochrane Library, Scopus and Web of Science and identified 6404 articles with the keywords: “carnitine” AND “exercises” OR “rehabilitation” OR “physical functional performance” OR “physical activity” OR “sports” OR “health” OR “healthy”. A total of 30 publications met the inclusion criteria and were included in the systematic review. The meta-analysis did not show any significant differences in serum lactate values at rest and after exercise in healthy subjects who took L-carnitine supplementation (p > 0.05). On the contrary, L-carnitine administration significantly changed maximal oxygen consumption (VO₂) at rest (p < 0.005), serum free and total carnitine at rest and after exercise (p < 0.001). The dosage of supplementation that obtained a significant change in serum total carnitine was 2 g/dL for 4 weeks at rest, 1 g/dL for 3 weeks after exercise, and in serum free carnitine was 2 g/dL for 3 weeks and 2 g/dL for 4 weeks at rest. Based on our study, serum total and free carnitine at rest and after exercise, and VO₂ at rest could be used to clinically follow individuals during physical activity and rehabilitation programs. Moreover, the supplementation should have a correct dosage to have maximum effect. Other robust trials are needed to find the best dosage to obtain positive results in metabolic parameters and in physical performance. Full article

High blood pressure (HBP) has been associated with several complications and causes of death. The objective of the study was to analyze the hemodynamic responses in Paralympic bench press powerlifting (PP) and conventional powerlifting (CP) before and after training and up to 60 minutes (min) after training. Ten PP and 10 CP athletes performed five sets of five repetition maximal bench press exercises, and we evaluated systolic, diastolic, and mean blood pressure (SBP, DBP, and MBP, respectively), heart rate (HR), heart pressure product (HPP), and myocardial oxygen volume (MVO₂). The SBP increased after training (p < 0.001), and there were differences in the post training and 30, 40, and 60 min later (p = 0.021), between 10 and 40 min after training (p = 0.031, η²_p = 0.570), and between CP and PP (p =0.028, η²_p = 0.570). In the MBP, there were differences between before and after (p = 0.016) and 40 min later (p = 0.040, η²_p = 0.309). In the HR, there was a difference between before and after, and 5 and 10 min later (p = 0.002), and between after and 10, 20, 30, 40, 50, and 60 min later (p < 0.001, η²_p = 0.767). In HPP and MVO₂, there were differences between before and after (p = 0.006), and between after and 5, 10, 20, 30, 40, 50, and 60 min later (p < 0.001, η²_p = 0.816). In CP and PP, there is no risk of hemodynamic overload to athletes, considering the results of the HPP, and training promotes a moderate hypotensive effect, with blood pressure adaptation after and 60 min after exercise. Full article

The amount of experience with ultrasonography may influence measurement outcomes while images are acquired or analyzed. The purpose of this study was to identify the interrater reliability of ultrasound image acquisition and image analysis between experienced and novice sonographers and image analysts, respectively. Following a brief hands-on training session (2 h), the experienced and novice sonographers and analysts independently performed image acquisition and analyses on the biceps brachii, vastus lateralis, and medial gastrocnemius in a sample of healthy participants (n = 17). Test–retest reliability statistics were computed for muscle thickness (transverse and sagittal planes), muscle cross-sectional area, echo intensity and subcutaneous adipose tissue thickness. The results show that image analysis experience generally has a greater impact on measurement outcomes than image acquisition experience. Interrater reliability for measurements of muscle size during image acquisition was generally good–excellent (ICC_2,1: 0.82–0.98), but poor–moderate for echo intensity (ICC_2,1: 0.43–0.77). For image analyses, interrater reliability for measurements of muscle size for the vastus lateralis and biceps brachii was poor–moderate (ICC_2,1: 0.48–0.70), but excellent for echo intensity (ICC_2,1: 0.90–0.98). Our findings have important implications for laboratories and clinics where members possess varying levels of ultrasound experience. Full article

Purpose: The purpose of this study was to determine whether session rating of perceived exertion-derived training load (sRPE-TL) correlates with GPS-derived measures of external load in National Collegiate Athletics Association (NCAA) Division I female soccer athletes. Methods: Twenty-one NCAA Division 1 collegiate women’s soccer athletes (11 starters, 10 non-starters; 65.1 ± 7.2 kg, 168.4 ± 7.9 cm, 20.3 ± 1.5 yrs) volunteered to take part in this study. Data for this study were collected over the course of 16 weeks during the 2018 NCAA women’s soccer season. External load and heart rate (HR) data were collected during each training session and match during the season. At least 30 min after the end of an activity (e.g., match or practice), athletes were prompted to complete a questionnaire reporting their perceived exertion for the session. sRPE-TL was calculated at the end of the season by multiplying perceived exertion by the respective session duration. Results: sRPE-TL was very strongly correlated with total distance, distance covered in velocity zones 1–3, the number of accelerations in zones 4 and 5, total PlayerLoad™, and PlayerLoad™. For internal load, sRPE-TL correlated very strongly (0.70 ≤ |r| < 0.90) with Edward’s and Bannister’s TRIMP and strongly (0.50 ≤ |r| < 0.70) with duration spent in in heart rate zones 5 and 6 (80–90% and 90–100% max HR, respectively) while correlations with maximum HR (bpm), mean HR (bpm), and mean HR (%) and sRPE-TL were moderate (0.30 ≤ |r| < 0.50). Conclusions: In NCAA Division I women soccer, sRPE-TL is strongly associated with external measures of workload. These relationships were stronger during match play, with acceleration load and total distance exhibiting the strongest relationship with sRPE-TL. Full article

The aims of the present research were to estimate the age of peak performance (APP) and to examine the role of previous experience at the world-level open water race performances. Finishing positions and age of swimmers (639 females and 738 males) in the 10-km events of World Championship (WCH) and Olympic Games (OG) from 2000 to 2019 were obtained from the official results websites. Years of previous experience were computed using the number of previous participations in WCH or OG. APP was estimated using quadratic models of the 10th percentile top race positions and resulted in 28.94 years old for males (R² = 0.551) and 27.40 years old for females (R² = 0.613). Regression analysis revealed an improvement of 1.36 or 8.19 finishing positions for each additional year of age or experience, respectively (R² = 0.157). However, significant differences (p < 0.001) between age and experience showed that the swimmer’s age became less relevant for performance as years of experience increased. These results, in terms of age, are in line with other mass-start disciplines of similar duration (≈2 h) and, in terms of experience, confirm the importance of previous participation in improving tactical decision making during open water races. Full article

The aim of the present study was to evaluate the effects of arm-crank induced priming on subsequent 20 min Functional Threshold Power Test among 11 well-trained male cyclists (18.8 ± 0.9 years; 182 ± 5 cm; 73.0 ± 6.6 kg; V˙O_2max 67.9 ± 5.1 mL·kg⁻¹·min⁻¹). Participants completed an incremental test and two maximal performance tests (MPTs) in a randomized order. Warm-up prior to MPT_low consisted of 20 min aerobic exercise and 25 s high-intensity all-out arm crank effort was added to warm-up in MPT_high. Constant intensities for the first 17 min of MPT were targeting to achieve a similar relative fatigue according to participants’ physiological capacity before the last 3 min all-out spurt. Final 3 min all-out spurt power was 4.94 ± 0.27 W·kg⁻¹ and 4.85 ± 0.39 W·kg⁻¹ in MPT_low and MPT_high, respectively (not statistically different: p = 0.116; d = 0.5). Blood lactate [La] levels just before the start were higher (p < 0.001; d = 2.6) in MPT_high (5.6 ± 0.5 mmol·L⁻¹) compared to MPT_low (1.1 ± 0.1 mmol·L⁻¹). According to V˙CO₂ and net [La] data, significantly higher anaerobic energy production was detected among MPT_low condition. In conclusion, priming significantly reduced anaerobic energy contribution but did neither improve nor decrease group mean performance although effects were variable. We suggest priming to have beneficial effects based on previous studies; however, the effects are individual and additional studies are needed to distinguish such detailed effects in single athletes. Full article

Introduction: It is common for postmenopausal women to receive a vitamin D supplementation prescription to assist in preventing future falls and to maintain bone health. However, the association between vitamin D supplementation and physical fitness components has not been studied in older women with diabetes. Objective: We examined the influence of 12 months of vitamin D supplementation on the components of physical fitness in postmenopausal women with type 2 diabetes mellitus (T2DM). Methods: Thirty-five postmenopausal women (62.48 ± 7.67 years; 154.6 ± 5.11 cm; 73.93 ± 15.43 kg; 31.13 ± 5.82 BMI) with a diagnosis of T2DM participated in this longitudinal study where participants were supplemented with 1000 IU/day of vitamin D over 12 months. Subjects performed fasting blood samples, anthropometric assessments, body composition, clinical exams, and physical tests at 6-month intervals (P0, P6, and P12). Results and Conclusion: Vitamin D supplementation alone was effective in postmenopausal women in increasing serum vitamin D levels, altering muscle strength levels, promoting improvements in muscle function, as well as preventing and controlling fragility caused by T2DM and aging. Full article

(1) Background: Paralympic Powerlifting (PP) is a Paralympic modality that is predominantly about developing maximal force, as there are athletes who lift three times their body weight. Our objective was to evaluate the averages of the velocity for 30% and 50% of 1 Maximum Repetition (1 RM) on different amplitudes of the footprint in PP athletes; (2) Methods: The intervention happened over two weeks, with the first being devoted to the familiarization and testing of 1 RM, while in the second week, through the use of a linear Encoder, tests of velocity average (VA), velocity average propulsive (VAP), and velocity peak (VP) were carried out with loads of 30% and 50% of a maximum repetition 1 RM for 1× of the biacromial distance (BAD) 1.3 × BAD, 1.5 × BAD; (3) Results: There was a significant difference in the average velocity of 1 × BAD (1.16 ± 0.14 m/s, 1.07–1.26 IC; η2p 0.20) when compared to 1.3 × BAD (1.00 ± 0.17 m/s, 0.90–1.09 IC; η2p 0.20) over 30% of 1 RM. For the other velocity variables for 30% and 50% of 1 RM with different grip amplitudes, there were no significant differences; (4) Conclusions: In PP, the 1 × BAD footprint contributes significantly to VA at 30% of 1 RM when compared to the 1.3 × BAD and 1.5 × BAD footprints. For loading at 50% of 1 RM the VA, VAP and VP decreased when compared to 30% of 1 RM, to the extent that the VAP and VP generated with the 1.3 × BAD and 1.5 × BAD footprints were higher than those with 1 × BAD, other than for VA 50% of 1 RM, where the 1 × BAD footprint was superior to the others. Full article

(1) Background: warm-ups precede physical exertion and has been shown to have positive and negative effects on performance. Positive effects include elevating body temperature, heart rate, and VO₂. Negative effects include increasing fatigue and blood lactate concentration. The most effective warm-up format is still unknown, particularly in competitive swimming. The purpose of this systematic review was to determine the most beneficial warm-up for maximal performance in sprint swimming events; (2) Methods: a structured search was carried out following the Preferred Reporting Items for Systematic review and Meta-Analyses (PRISMA) guidelines in the PubMed, SportDiscus, and Google Scholar databases until March 2021. Studies with double-blind and randomized designs in which different types of warm-up were compared to each other or an identical placebo condition (no warm-up) were considered. Fourteen published studies were included. The effects of warm-up on sprint swimming performance, rating of perceived exertion (RPE) and blood lactate concentration (La⁻) were investigated. (3) Results: in half of the studies, swimmers performed significantly better after a regular warm-up; however, the effect of warm-up on performance was small. Warm-ups had a medium to large effect on RPE and a small to medium effect on La⁻. (4) Conclusions: the findings of this review suggest that warm-ups do influence performance, although the magnitude is small. Future studies are needed in larger populations to clarify whether warm ups improve swim performance, to what extent, and the potential role of variables related to participant characteristics and swimming competitions. Full article

The objective of this research was to evaluate the protections taken by ski and snowboard recreational athletes of the winter stations Sierra Nevada and Alto Campoo (Spain), regarding gender, age, and practiced sport. A total of 520 users participated, Sierra Nevada (n = 306 (58.8%)); Alto Campoo (n = 214 (42.2%)), 257 of them were men (49.4%) and 263 (50.6%) were women, from 6 to 64 years old, classified by 4 stages of development (Childhood (n = 106 (20.4%)); Teenagers (n = 110 (21.2%)); Youth (n = 101 (19.4%)); Adults (n = 203 (39.0%))). For the data collection, an Ad Hoc questionnaire was used (Socio-demographic data, use/no use of protection). The data revealed that 23.5% of the participants did not use any protection. Regarding the development stage, 1% of the children did not use any protection, neither did 3.1% of the teenagers, 6.7% of the youth, or 12.7% of the adults (p < 0.001). Regarding gender, a total of 17.1% of men did not use protection, and regarding women, 6.3% of them did not use it (p < 0.001). In relation to the practiced sport, 15.8% of the skiers did not use it against 7.7% of the snowboarders (p = 0.006). The use of protection for the practice in winter sports is not enough to reduce the injury risk in these sports and, in the worst cases, fatal accidents. Full article

The change of direction (COD) ability is a task-specific skill dependent on different factors such as the degree of the turn, which has led to differentiating CODs as more force- (>90°) or velocity-oriented (<90°). Considering force and velocity requirements is of importance when designing sport-specific training programs for enhancing COD performance. Thus, 25 female handball and soccer players participated in this study, which investigated the association between three different strength and plyometric exercises and force- and velocity-oriented COD performance. By utilizing the median split analysis, the participants were further divided into a fast (n = 8) and a slow (n = 8) COD group, to investigate differences in step kinematics between fast and slow performers. The correlational analysis revealed that the bilateral back squat and unilateral quarter squat were significantly associated with several force- and velocity-oriented COD performance (r = −0.46 to −0.64), while the association between plyometric and COD performance was limited (r < 0.44). The fast COD group revealed higher levels of strength, jump height, peak velocities, higher step frequencies, shorter ground contact times, and greater acceleration and braking power (d > 1.29, p < 0.03). It was concluded that the observed correlation between strength and COD performance might be due to stronger athletes being able to produce more workload in a shorter time, which was supported by the step kinematics. Full article

Trunk positioning and unexpected perturbations are high-risk conditions at the time of anterior cruciate ligament injury. The influence of trunk positioning on motor control responses to perturbation during dynamic performance is not known. We tested the influence of trunk position on feedforward and feedback control during unexpected perturbations while performing a novel single-limb squatting task. We also assessed the degree that feedforward control was predictive of feedback responses. In the flexed trunk condition, there were increased quadriceps (p < 0.026) and gluteus medius long-latency reflexes (p < 0.001) and greater quadriceps-to-hamstrings co-contraction during feedforward (p = 0.017) and feedback (p = 0.007) time bins. Soleus long-latency reflexes increased more than 100% from feedforward muscle activity regardless of trunk condition. Feedforward muscle activity differentially predicted long-latency reflex responses depending on the muscle (R²: 0.47–0.97). These findings support the concept that trunk positioning influences motor control responses to perturbation and that feedback responses may be invariant to the feedforward control strategy. Full article

In badminton, power production can be enhanced through the fundamental practice of a dynamic warm-up with resistance conditioning activity to induce a post-activation performance enhancement (PAPE) effect. The use of heavy resistance exercise in the form of heavy weights to induce PAPE during competition is not logistically practical in the badminton arena. Thus, there is a need to investigate the use of easily available alternative preconditioning stimuli to induce a similar potentiating effect in badminton-specific performance. This study adopted a repeated-measures design of three warm-up conditions: control (CON), weighted wearable resistance (WWR), and resistance band variable resistance (BVR). Fourteen badminton players from the national training squad (11 males, 3 females, age 18 ± 1 y) completed the experimental sessions in random order. Change of direction speed (CODS) and smash velocity (SV) tests were performed at five timepoints—baseline test after the warm-up and at the end of each of the four exercise blocks of a simulated match play protocol. CODS was significantly faster under the two resistance warm-up conditions (WWR and BVR) compared to the CON condition at baseline (−0.2 s ± 0.39 and −0.2 s ± 0.46, p = 0.001 and 0.03, g = 0.47 and 0.40, respectively), but there were no differences at the other timepoints (all p > 0.05). SV was significantly faster for all the four exercise blocks than at baseline under all three warm-up conditions (p = 0.02), but there were no differences in SV between the three warm-up conditions across all the five measured timepoints (p = 0.15). In conclusion, implementing resistance (~10% body weight) in sport-specific plyometric exercises using WWR or BVR during warm-up routines may induce PAPE effects on the change of direction speed but not smash velocity, in well-trained badminton players, as compared with the same warm-up exercises using bodyweight (i.e., CON condition). The positive effects of CODS were, however, observed only at the start of the match and possibly lasted for up to between 5 and 10 min of match play. Full article

The mechanical properties of knee flexors and extensors in 15 collegiate male soccer players following different warm-up protocols [small-sided games (SSG), dynamic (DYN), and plyometric (PLY)] were evaluated. Tensiomyography (TMG) was used to assess contraction time (Tc), delay time (Td) and maximal displacement (Dm) of the rectus femoris (RF) and biceps femoris (BF) of both legs before and after each warm-up, while countermovement jump height variables, 20 m sprint, t-test and sit-and-reach were measured following the warm-ups. TMG was analyzed using a three-way [condition × time × leg] ANOVA, while performance variables were analyzed with a repeated measures ANOVA. Main effects of time were observed for BF-Tc (p = 0.035), RF-Td (p < 0.001), and BF-Td, (p = 0.008), and a main effect of condition was seen for RF-Tc (p = 0.038). Moreover, participants’ 20 m sprint improved following SSG (p = 0.021) compared to DYN and PLY. Sit-and-reach was greater following PLY (p = 0.021). No significant interactions were noted for the measured TMG variables. Warm-up-specific improvements were demonstrated in sprint speed and flexibility following SSG and PLY, respectively. The present study revealed changes in certain TMG measures following the warm-ups that suggest enhanced response of lower leg muscles regardless of specific activities used. Full article

This study examined the associations between asymmetric handgrip strength (HGS) and multimorbidity in American adults. Secondary analyses of data from persons aged at least 40 years from the 2011–2012 and 2013–2014 waves of the National Health and Nutrition Examination Survey were conducted. A handheld dynamometer collected HGS on each hand and persons with a strength imbalance >10% between hands were classified as having asymmetric HGS. Adults with the presence of ≥2 of the following conditions had multimorbidity: cardiovascular disease, chronic obstructive pulmonary disease, chronic kidney disease, asthma, arthritis, cancer, obesity, stroke, hypertension, high cholesterol, and diabetes. Of the n = 3483 participants included, n = 2700 (77.5%) had multimorbidity. A greater proportion of adults with multimorbidity had HGS asymmetry (n = 1234 (45.7%)), compared to persons living without multimorbidity (n = 314 (40.1%); p < 0.05). Relative to individuals without asymmetry, adults with asymmetric HGS had 1.31 (95% confidence interval (CI): 1.03–1.67) greater odds for multimorbidity. Moreover, persons with HGS asymmetry had 1.22 (CI: 1.04–1.44) greater odds for accumulating morbidities. Asymmetric strength, as another indicator of diminished muscle function, is linked to chronic morbidity status. Healthcare providers should recommend healthy behaviors for reducing asymmetries to improve muscle function and mitigate morbidity risk after completing asymmetry screenings. Full article