Maximal Isometric Strength Research Articles

Efectos de dos programas de ejercicios resistidos en la aptitud física relacionada con la salud de mujeres obesas con síntomas de algia en las rodillas

Introduction: Overweight negatively impacts the cardiovascular system and osteomyoarticular, promoting pain in the joints of the lower limbs. Therefore, strategies have been applied to reduce overweight through lifestyle changes. Objective: to investigate the effects of two multidisciplinary intervention programs on the health-related physical fitness of obese women with pain symptoms in the knees. Methods: Women between 40 and 59 years of age with obesity (n=59) were evaluated in the pre- and post-intervention time regarding anthropometry, body composition, physical fitness, level of disability in the knee and hip, and health-related quality of life. A randomized clinical trial of parallel groups was conducted, using two resistance exercise programs and food re-education, for eight weeks. All participants received the same nutritional intervention content and for physical exercises were randomized into two groups, G1 being the "strength group" using machines (n=30), and G2 being the "functional training" group (n=29). Twenty-eight women (G1=18 + G2=10) were included in the final analyses. The groups and time were evaluated by two-way analysis of variance, with repeated measures. A p < 0.05 was assumed for all analyses. Results: a time effect was identified, with higher values for maximum isometric lumbar-traction strength (MILTS), after the intervention period in both groups (p < 0.05). However, for the other variables investigated, no significant differences were identified (p > 0.05). Conclusion: The absence of significant results for all variables, except FIMTL, may be justified by the moderate adherence of the participants to interventions (~59% to 66%) since the study was conducted during the period of social isolation (COVID-19). However, it is believed that the intervention models were positive in maintaining the variables studied.

Effects of age and sex on association between toe muscular strength and vertical jump performance in adolescent populations.

Toe muscular strength plays an important role in enhancing athletic performance because the forefoot is the only part of the body touching the ground. In general, muscular strength increases with age throughout adolescence, and sex-related difference in muscular strength becomes evident during childhood and adolescence. However, toe muscular strength is known to be levelled off after late adolescence in both sexes. For adolescent populations, therefore, the association of toe muscular strength with physical performance might differ with age and/or sex. This study aimed to investigate differences in relationships between toe muscular strength and vertical jump performance across sex and age in adolescent populations. The maximum isometric strength of the toe muscles and vertical jump height (VJ) were assessed in 479 junior high school students (JH) aged 12-14 years (243 boys and 236 girls) and 465 high school students (HS) aged 15-18 years (265 boys and 200 girls). Two types of measurements were performed to evaluate the toe muscular strength: toe gripping strength (TGS) with the metatarsophalangeal joint in the plantar flexed position and toe push strength (TPS) with the metatarsophalangeal joint in the dorsiflexed position. TGS and TPS were normalized to body weight. Two-way ANOVA showed that TGS had significant main effects of sex (boys > girls) and age (HS > JH) while TPS only had a significant main effect of sex (boys > girls). When the effects of sex and age were separately analyzed, VJ was significantly correlated with TGS in JH girls, HS girls, and JH boys (r = 0.253-0.269, p < 0.05), but not in HS boys (r = 0.062, p = 0.3351). These results suggest that toe muscular strength is relatively weakly associated with vertical jump performance in adolescent boys and girls, but the association would not be established in high school boys.

The Effects of a Five-Month Lockdown Due to COVID-19 on Physical Fitness Parameters in Adolescent Students: A Comparison between Cohorts.

Background: This study examined the effects of a five-month lockdown due to COVID-19 pandemic on physical fitness parameters in urban adolescent male and female students. Methods: Two hundred and ninety-three male and female students (age: 15.8 ± 0.3 years) who attended the fourth grade of the same high school during the years 2016–2017 (first control group), 2018–2019 (second control group) and 2020–2021 (lockdown group) took part in the present study. Results: The percentage of overweight and obese students, according to body mass index, increased in males from 16.0% (2016–2017) and 14.6% (2018–2019), to 36.7% in 2020–2021 (p < 0.01), and in females from 8.6% (2016–2017) and 7.0% (2016–2017), to 25.6% in 2020–2021 (p < 0.01). Lower body fitness, as assessed by jumping, sprinting and agility tests, was impaired for both males and females after the lockdown compared with the 2016–2017 and 2018–2019 cohorts (vertical jumps: 10.4–15.1%; p < 0.01; d = 0.58–1.01, 30 m sprint: 3.7–4.9%; p < 0.01; d = 0.62–0.74; 505 agility test: from 6.1% to 9.4%; p < 0.01; d = 0.80–1.04). However, flexibility and performance in upper-body fitness tests (handgrip maximum isometric strength and medicine ball throws with different loads) was significantly reduced only in males after the lockdown (p < 0.05 to 0.01). Conclusions: These results suggest that a five-month lockdown negative influenced the physical fitness of adolescent students. Notably, greater reductions were observed in upper body strength, power and flexibility in males than in females. These results highlight the need to maintain strength, power and body mass during long periods of inactivity in adolescent populations.

Physical capacities assessment in critically ill patients: An exploratory study

BackgroundThe severity of muscle weakness after critical illness is very heterogeneous. To identify those patients who may maximally benefit from early exercises would be highly valuable. This implies an assessment of physical capacities, comprised at least of strength measurement and functional tests. ObjectivesThe objective of this study was to investigate the relationship between muscle strength and functional tests in an intensive care unit (ICU) setting. MethodsAdults with ICU length of stay ≥2 days were included. Handgrip strength (HG) and maximal isometric quadriceps strength (QS) were assessed using standardised protocols as soon as patients were alert and able to obey commands. At the same time, their maximal level of mobilisation capabilities and their autonomy were assessed using ICU Mobility Scale (ICU-MS) and Barthel Index, respectively. ResultsNinety-three patients with a median age of 64 [57–71.5] years, body mass index of 26.4 [23.4–29.6] kg/m2, and Simplified Acute Physiology Score II of 33 [27.7–41] were included. Absolute and relative QS were, respectively, 146.7 [108.5–196.6] N and 1.87 [1.43–2.51] N/kg. HG was 22 [16–31] kg. The ICU-MS score was 4 [1–5]. A significant positive correlation was observed between HG and absolute QS (rs = 0.695, p < 0.001) and between HG and relative QS (rs = 0.428, p < 0.001). The ICU-MS score correlated with HG, with a weak positive relationship (rs = 0.215, p = 0.039), but not with QS. The ICU-MS score did not statistically differ between the weakest and strongest patients for absolute or relative QS, but was lower in patients with the lowest HG values (p = 0.01). A weak positive correlation was observed between the Barthel Index and muscle strengths (maximum rs = 0.414, p < 0.001). ConclusionsThe present results suggest that, during ICU stay, there is no strong association between muscle strength and functional test such as the ICU-MS or Barthel Index. Muscle dynamometry and functional tests are probably complementary tools for physical capacities quantification.

Relationship between vastus medialis Hoffmann reflex excitability and knee extension biomechanics during different tasks in women with patellofemoral pain

BackgroundImpaired knee extension biomechanics and spinal excitability have been reported in women with patellofemoral pain, but their relationship has not been explored. A significant relationship between them could indicate the need for investigating the potential benefits of disinhibitory interventions for women with patellofemoral pain. Thus, this study aimed to investigate the relationship between vastus medialis Hoffmann reflex and (1) maximal isometric, concentric and eccentric knee extensor strength and rate of torque development; (2) knee extensor torque steadiness; and (3) knee extensor moment during functional tasks; in women with patellofemoral pain. MethodsSpinal excitability of twenty-four participants was assessed by the amplitude of maximal vastus medialis Hoffmann reflex. Knee extensor strength, rate of torque development and torque steadiness were assessed using an isokinetic dynamometer. Knee extensor moment during step-down and stair descent tasks were obtained using a three-dimensional motion analysis system. FindingsA moderate negative relationship was found between vastus medialis Hoffmann reflex and knee extensor torque steadiness (r = −0.35; p = 0.05); whereas a moderate positive relationship was found with maximal isometric knee extensor strength (r = 0.37; p = 0.044). No significant relationships were found between vastus medialis Hoffmann reflex and the other variables. InterpretationOur findings provide insight on the relationship between spinal excitability and neuromuscular control of maximal and submaximal isometric torque production in women with patellofemoral pain. Conversely, spinal excitability does not seem to be related with dynamic torques and moments of the knee extensors in women with patellofemoral pain.

Stretch-Shortening Cycle Performance and Muscle-Tendon Properties in Dancers and Runners.

The purpose of this investigation was to elucidate whether ankle joint stretch-shortening cycle performance, isometric and isokinetic plantarflexion strength, and maximal Achilles tendon force and elongation differ between dancers, endurance runners, and untrained controls. To differentiate between dancers, endurance runners, and controls, the authors measured maximal Achilles tendon force and elongation during isometric ramp contractions with ultrasonic imaging, maximal isometric and isokinetic plantarflexion strength with dynamometry, and stretch-shortening cycle function during countermovement hopping and 30-cm drop hopping with a custom-designed sled. The Achilles tendon of dancers elongated significantly (P ≤ .05) more than runners and controls. Dancers were significantly stronger than controls during isometric contractions at different ankle angles. Concentric and eccentric strength during isokinetic contractions at 60°·s-1 and 120°·s-1 was significantly higher in dancers and runners than controls. Dancers hopped significantly higher than runners and controls during hopping tasks. Dancers also possessed significantly greater countermovement hop relative peak power, drop hop relative impulse, and drop hop relative peak power than controls. Finally, dancers reached significantly greater velocities during countermovement hops than runners and controls. Our findings suggest dancing and running require or likely enhance plantarflexion strength. Furthermore, dancing appears to require and enhance ankle joint stretch-shortening cycle performance and tendon elongation.

Acute Effects of Static Self-Stretching Exercises and Foam Roller Self-Massaging on the Trunk Range of Motions and Strength of the Trunk Extensors

Although the effectiveness of static self-stretching exercises (SSSEs) and foam roller self-massaging (FRSM) in joint range of motion and muscle strength of the lower limbs has been extensively investigated, little is known about their effectiveness on the posterior trunk muscles. The present study aimed to investigate the acute effects of two 7-min SSSEs and FRSM intervention protocols on the range of trunk movements and the strength of the trunk extensors. Twenty-five healthy active males (n = 14) and females (n = 11) performed each intervention separately, one week apart. The range of motion (ROM) of the trunk-hip flexion (T-HF), the ROM of the trunk side-flexion (TSF) and rotation (TR) bilaterally, as well as the isometric maximum strength (TESmax) and endurance (TESend) of the trunk extensors were measured before and after each intervention. The ROMs of T-HF, TSF, and TR were significantly increased following both SSSEs and FRSM. The TESmax and TESend were also significantly increased after FRSM, but decreased following SSSEs. While both interventions were effective in increasing the range of motion of the trunk, a single 7-min session of FRSM presented more advantages over a similar duration SSSEs protocol due to the increase in the strength of the trunk extensors it induced.

Carbohydrate Mouth Rinsing Does Not Alter Central or Peripheral Fatigue After High-Intensity and Low-Intensity Exercise in Men.

Black, CD, Haskins, KR, Bemben, MG, and Larson, RD. Carbohydrate mouth rinsing does not alter central or peripheral fatigue after high-intensity and low-intensity exercise in men. J Strength Cond Res 36(1): 142-148, 2022-Carbohydrate (CHO) mouth rinsing improves performance during endurance exercise. However, its ability to attenuate fatigue during strength-based exercise is less certain. This study sought to determine the effects of a CHO mouth rinse on torque production and voluntary activation (VA%) after high-intensity and low-intensity isometric exercise. Twelve male subjects (22.5 ± 2.3 years; 183.5 ± 6.5 cm; 82.2 ± 13.9 kg) completed 4 testing sessions in a double-blind crossover fashion. Knee extension maximal voluntary isometric strength (MVC) was assessed before(Pre), immediately (iPost-Ex), and 5 minutes (5-min Post Ex) after isometric exercise performed at 80% or 20% of MVC. An 8% CHO solution or placebo (PLA) was rinsed for 20 seconds after exercise. VA% was determined by twitch interpolation. A 2 condition (CHO vs. PLA) × 2 contraction intensity (20 vs. 80%) × 3 time (Pre, iPost Ex, and 5-min Post Ex) completely within subject-repeated measured analysis of variance was performed; statistical significance was set at p ≤ 0.05. Greater reductions in MVC were found at iPost-Ex after exercise at 20% compared with 80% of MVC (-25 ± 14% vs. -11 ± 8%; p < 0.001) as well as for VA% (-17 ± 14% vs. -8 ± 14%; p < 0.004). No differences were observed in the CHO vs. PLA condition (p ≥ 0.34). We were successful in eliciting differing levels of central and peripheral fatigue by exercising at a low and high intensity. Despite significantly larger declines in VA% after exercise at 20% of MVC, CHO mouth rinsing had no effects compared with placebo on any measured variable.

Knee Extensor Strength in Anterior Cruciate Ligament-Deficient Individuals Following Normal and Modified Squats: A Randomized Controlled Trial.

Jean, LMY, Gross, DP, and Chiu, LZF. Knee extensor strength in anterior cruciate ligament-deficient individuals following normal and modified squats: a randomized controlled trial. J Strength Cond Res 36(1): 47-54, 2022-Training with barbell squats, which load the quadriceps, increases knee extensor strength. Anterior cruciate ligament (ACL) injury results in a quadriceps avoidance substitution strategy, which may impair the efficacy of barbell squat training. Modified squats to promote quadriceps loading have been proposed to facilitate restoring knee extensor strength and function. This research compared resistance training using traditional squats (TRAD) versus traditional plus modified squats (EXP) in ACL-deficient individuals. Thirty-seven ACL-deficient individuals were randomly assigned to TRAD or EXP. Knee extensor function was assessed using maximum isometric strength testing and 3D motion analysis of sit-to-stand. Effect sizes for minimum meaningful improvement were established (d = 0.28-0.47). There were no significant differences between TRAD and EXP for knee extensor strength before, in response to, or after the training interventions (p > 0.05). Involved limb knee extensor strength increased at 15° (95% CI [0.09, 0.27] N·m·kgBM-1, d = 0.60), 30° (95% CI [0.25, 0.48] N·m·kgBM-1, d = 0.82), 45° (95% CI [0.32, 0.58] N·m·kgBM-1, d = 0.78), and 75° (95% CI [0.18, 0.46] N·m·kgBM-1, d = 0.54) knee flexion. Involved limb knee extensor net joint moment work in sit-to-stand (95% CI [0.034, 0.135] J·kgBM-1, d = 0.48) increased in both groups. Squat training was effective for increasing involved limb isometric knee extensor strength and knee extensor work performed in the sit-to-stand. Modified squats do not seem to provide additional benefit.

중년 남성의 근 체력 및 염증 수준과 백혈구 텔로미어 길이와의 관련성

This study was to investigate the effects of muscular fitness and inflammation level on telomere length in middle aged men. This study was conducted on 106 middle aged men. We examined muscle fitness, such as muscle mass, grip strength and maximal knee eccentric isometric strength (MKEIS), inflammation level including c-reactive protein (CRP) and lactate dehydrogenase (LDH), and telomere length. LDH level has shown a negative correlation with telomere length (r=-.289, p＜.01). When adjusted for age and muscle fitness related factors, as LDH level increased by 1 UI/L, the telomere length (T/S ratio) decreased by 0.0013 (p＜.01). When adjusted for age and obesity related factor such as BMI, percent of body fat, and waist circumference, as LDH level increased by 1 UI/L, telomere length (T/S ratio) decreased by 0.0014(p＜.01). When adjusted for all variable, as LDH level increased by 1 UI/L, telomere length (T/S ratio) decreased by 0.0012 (p＜.01). Overall, LDH as muscle damage marker influenced telomere length in middle-aged men.

Comparison of Maximum Isometric Strength, Proprioceptive, Dynamic Balance, and Maximum Angle by Applying the Fascial Distortion Model to Chronic Ankle Instability Subjects

Comparison of Maximum Isometric Strength, Proprioceptive, Dynamic Balance, and Maximum Angle by Applying the Fascial Distortion Model to Chronic Ankle Instability Subjects

Deficits in muscle cross-sectional area and maximal isometric force following a shark bite injury are not reflected in jumping performance

Introduction: Environmental changes and growing surfing populations have led to increases in the number of shark sightings and unprovoked shark attacks on surfers. We present a case study of a 26-year-old male (height 178.4cm, mass 67.3kg) who was bitten by a shark on his left lateral thigh whilst surfing. The surfer lost most of the muscle and skin of the distal 2/3 of his anterolateral thigh, including all of vastus lateralis and most of vastus intermedius and rectus femoris muscles. After 3 years of intensive physiotherapy and rehabilitation, the surfer returned to a high-level of competitive surfing and has remarkable physical function. We investigated the anatomical structure and function of his affected (A) and unaffected (UA) thigh muscles relative to his dynamic functional strength to understand the potential physical function that can be achieved despite substantial muscle loss. Methods: Muscle group cross-sectional area (CSA) for the quadriceps and hamstrings were measured using magnetic resonance imaging, with axial slices taken from ~50% of the distance between the lesser trochanter and the medial femoral condyle. A handheld dynamometer was used to assess the maximal isometric strength of the quadriceps muscles through resisted knee extension while the surfer was seated and the hamstring muscles through resisted knee flexion in a prone position. Dynamic strength and jumping performance were assessed by the surfer performing countermovement jumps (CMJ) on two force platforms. Data are reported as means ± standard deviations. Results: The surfer’s quadriceps CSA was substantially larger in the UA (8304.8mm2) compared to the A (2857.2mm2) limb, although there was little between-limb difference in hamstring CSA (UA: 3499.1mm2, A: 3273.6mm2). The surfer produced more maximal isometric quadriceps strength in the UA compared to the A limb (406.1±45.0N vs 205.9±12.6N). The surfer’s peak CMJ height was 34±1.0cm, with relative peak forces of 1.28±0.10N/BW and 0.82±0.03N/BW generated for the UA and A, respectively. Discussion: Differences in quadriceps muscle function between the limbs were consistent with the differences in anatomical structure, whereby lower quadriceps CSA resulted in lower maximal isometric quadriceps strength. This quadriceps strength deficit, however, was not reflected in the functional dynamic strength achieved in the CMJ because the surfer’s peak jump height was comparable to that of international-level competitive surfers. Differences in the between-limb peak forces were much less than differences in maximal isometric strength, suggesting that neuromuscular adaptations developed during rehabilitation might have contributed to the high-level of physical function the surfer achieved. Conflict of interest statement: The authors have no conflicts of interest to declare.

The Relationship between Modified Short Physical Performance Battery and Falls: A Cross-Sectional Study of Older Outpatients.

The Short Physical Performance Battery (SPPB) is a physical fall-risk screening tool and predictor of adverse health effects for the older. Its limited use in Japan is due to the relative ease for high-functioning older adults to achieve perfect scores. Japanese researchers thus created a community-based SPPB (SPPB-com). This study investigated whether the SPPB-com score can distinguish between older patients classified as “fallers” and “non-fallers.” Participants comprised 185 older outpatients aged 65 and above who self-reported their history of accidental falls and relevant physical activity. Fall risk was assessed using SPPB and SPPB-com. Handgrip strength, maximum isometric knee extensor strength, and maximum walking speed were measured as physical functions. Multivariate logistic regression and receiver-operating characteristic analyses determined criteria indicating faller status. Fallers were older and had lower physical function, physical activity, SPPB, and SPPB-com scores than non-fallers. Multivariate logistic regression analysis showed SPPB (OR 0.76, 95% CI 0.59–0.99, p = 0.045) and SPPB-com (OR 0.63, 95% CI 0.45–0.87, p = 0.005) scores were both independently associated with prior falls. The SPPB-com score may function as a fall-risk assessment tool for older outpatients, and its combined use with SPPB can increase the accuracy and precision of distinction between fallers and non-fallers.

Relationship between the colors of goggles and shoulder muscle strength in swimmers

Biography: Obtained a doctor of medicine on the theme of verifying the effect of therapeutic exercise in osteoarthritis. Rio Olympic games Artistic Swimming Japan national team trainer. I am interested in improvement of physical performance in swimming and cognitive science applied to sports. Background: Almost all studies on color reveal its effects on calculation tasks and work efficiency, and there are few fundamental studies on individual sports performance. Recently, some reports have indicated that unconsciously processed visual information affects the performance of sports. In this study, we focused on muscle exertion, which is directly related to sports performance, and studied the effect of different colors of goggles on muscle exertion of the upper limbs. Methods: Sixty-eight collegiate swimmers (mean age 19.4 ± 1.0 years) were recruited. Written informed consent was obtained from all participants. Subjects were made to randomly wear four differently colored goggles (red, blue, green, and transparent), and the upper limb muscle strength was measured using a hand-held dynamometer. The upper limb muscle strength was measured while lying down on a bed on the ground, and the maximum isometric muscle strength at the catch position, push position, and finish position were measured based on the phase separation of pull motions during swimming. SPSS was used for statistical processing, and the significance level was set at 5%. Results: The muscle strength of the catch position, push position, and finish position with the red goggles was 20.7 ± 5.8 kgf, 20.5 ± 6.2 kgf, and 11.7 ± 2.9 kgf, respectively. Similarly, muscle strength with the blue, green and transparent goggles was 20.5 ± 6.0 kgf, 20.5 ± 5.6 kgf, and 11.6 ± 3.1 kgf; 20.7 ± 5.8 kgf, 21.0 ± 6.0 kgf, and 11.4 ± 3.0 kgf ; and 20.6 ± 6.1 kgf, 20.4 ± 6.0 kgf, and 11.5 ± 3.1 kgf, respectively. Statistical analysis showed significant difference in the muscle strength between green goggles and transparent goggles at the push position (p < 0.05). However, there was no significant difference in the other colors or positions. Discussion: Several studies have reported that the color of uniforms affects the winning rate and performance in sports (Hopkin, 2005). Red color has been found to be advantageous, possibly because it increases the fighting spirit associated with the secretion of testosterone. In this study, it was not possible to prove that red is a best color for muscular exertion. However, this study suggests that the color of goggles has some influence on muscular exertion in a specific limb position. Further studies are needed to study the effects of colors on hormones, autonomic nerves, and brain activity. Conflicts of interest: This work was supported by JSPS KAKENHI Grant Numbers 19K11496.

Which physical attributes discriminate between faster and slower elite cricket pace bowlers of each sex?

Background: Ball release speed is an important quality of successful performance in pace bowlers. There is limited evidence available regarding the association between physical attributes and ball release speed in elite male pace bowlers, and no studies that have investigated the physical attributes associated with ball release speed in female pace bowlers. The purpose of this study therefore, was to elucidate which physical attributes discriminates between faster and slower elite cricket pace bowlers of each sex. Methods: Ball release speed and physical testing data from sixty-three elite male and thirty-one elite female pace bowlers from the 2014/15 season to the 2020/21 season were retrospectively analysed. Pace bowlers were classified as either “slower” (females: < 97.8 km/h; males: < 122.9 km/h) or “faster” (females: > 97.8 km/h; males: > 122.9 km/h) via a median split. From the five physical tests, six absolute variables were collected. Each absolute variable was normalised to body weight resulting in a total of twelve physical attributes. These twelve physical attributes were compared between the slower and faster groups for each sex. The differences between groups were compared using magnitude-based inferences (Cohen’s d). Results: Faster male bowlers produced greater absolute (d = 0.25) and relative (d = 0.62) peak force in the isometric mid-thigh pull (IMTP), as well as greater absolute (d = 0.39) and relative (d = 0.61) countermovement jump (CMJ) height compared to their slower counterparts. Faster female bowlers also produced greater absolute (d = 0.68) and relative (d = 0.77) peak force in the IMTP, greater 1RM bench pull strength (d = 0.45) and superior run of three performance (relative average, d = 1.22; relative best, d = 1.12; average, d = 0.49; and best d = 0.40) and superior 1RM bench pull strength (d = 0.45). Discussion: Greater lower body maximal isometric strength discriminates between faster and slower bowlers, irrespective of sex. Lower body power (assumed via CMJ height) appears to be an important physical attribute for faster male bowlers. Superior anaerobic capacities separated faster female pace bowlers from their slower counterparts. Further research should assess rate of force development qualities of the lower and upper body musculature associated with desirable biomechanics, to provide a more complete understanding of the physical attributes that may distinguish between slower and faster bowlers of each sex. Conflict of interest statement: The authors would like to acknowledge Dr Anna Saw, Dr Kevin Sims and Dr Alex Kountouris from Cricket Australia, for the support, access and use of ball speed and physical testing data. This work was supported by a Deakin University Postgraduate Research Scholarship as a part of a doctorate degree.

Sex differences in neck strength and head impact kinematics in university rugby union players

ABSTRACT Globally, over three million women participate in rugby union, yet injury prevention and training strategies are predominantly based on androcentric data. These strategies may have limited generalisability to females, given the cervical spine is more susceptible to whiplash and less adept at resisting inertial loading. A total of 53 university rugby union players (25 female, 28 male, 20.7 ± 1.8 years) had their isometric neck strength measured. Bespoke instrumented mouthguards were used to record the magnitude of head impact events in six female and seven male competitive matches. Mean female maximal isometric neck strength was 47% lower than male. Independent samples Mann–Whitney U tests showed no significant differences for peak linear head acceleration (female: median 11.7 g, IQR 7.9 g; male: median 12.5 g, IQR 7.0 g p=.23) or peak rotational head acceleration (female: median 800.2 rad·s−2, IQR 677.7 rad·s−2; male: median 849.4 rad·s−2, IQR 479.8 rad·s−2; p=.76), despite the mean male body mass being 24% greater than female. Coded video analysis revealed substantial differences in head-impact mechanisms; uncontrolled whiplash dominated >50% of all recorded female impact events and <0.5% in males. Direct head-to-ground impacts comprised 26.1% of female and 9.7% of male impacts, with whiplash occurring in 78.0% and 0.5%, respectively. Overall, the data provided in this study do not support the generalisation of male-derived training and injury-prevention data to female rugby athletes. These results suggest a considerable research effort is required to identify specific weakness of female rugby players and derive appropriate training, injury prevention and return to play protocols. Highlights Video analysis revealed substantial differences in head-impact mechanisms, with uncontrolled whiplash dominating >50% of all recorded female impact events but rarely in males. Isometric neck strength was 47% lower in female players than males. Direct head-to-ground impacts accounted for 26.1% and 9.7% of female and male impacts, with whiplash occurring in 78.0% and 0.5%, respectively.

The immediate effect of different loads does not alter muscle co-activation of the upper limb in young adults with dyskinetic cerebral palsy.

There is insufficient information on muscle co-activation in the upper limbs to help healthcare providers develop treatment programs for patients with dyskinetic cerebral palsy (DCP). Is the degree of muscle co-activation greater in adults with DCP than in healthy individuals? Does the use of different arm weights modify co-contraction in individuals with PCD? Fourteen healthy individuals (control group [CG]) and 14 individuals with DCP (dyskinetic group [DG]) participated in the study. The degree of muscle co-activation of the dominant limb during drinking from a mug was compared between the two groups. The task was divided into a going, adjusting, and returning phase. In the DG, an analysis was also performed on using an arm weight during the functional task. The loads corresponded to 10, 20, and 30 % of maximum isometric muscle strength measured in each participant. In comparing the two groups, the DG exhibited a greater muscle co-activation in the shoulder and elbow muscles during the going phase, the shoulder, elbow, and wrist during the adjusting phase; and the elbow during the returning phase. The DG also showed a greater mean index of curvature (MIC), time to perform the movement phases, and lesser mean velocity (Vm) to drinking. In analyzing the DG's arm weight, no effect on co-activation, MIC, time to perform the movement phases, and Vm to drinking were found with the loads tested (p > 0.05). Muscle co-activation is increased in adults with DCP in comparison to healthy individuals. Moreover, arm weight during the functional activity of drinking from a mug did not alter co-activation, although an immediate effect was expected.

The Effect of the FIFA 11 + with Added Neck Exercises on Maximal Isometric Neck Strength and Peak Head Impact Magnitude During Heading: A Pilot Study.

BackgroundHigher neck strength has been postulated to reduce head impact magnitude during purposeful heading in football.ObjectivesThis pilot trial explored the effect of a neck exercise programme on (1) neck strength and (2) head impact magnitude during heading in male and female adolescent football players.MethodsBoys and girls (aged 12–17 years) were randomised by team to the intervention (5 weeks of supervised neuromuscular neck exercises integrated into part 2 of the FIFA 11 + , completed three times per week) or the control group (usual part 2 of the FIFA 11 + , no neck exercises). Outcomes included isometric neck strength and head impact magnitude (peak linear acceleration and peak angular velocity) during standardised heading from a throw-in (at baseline and 6 weeks) plus completion of an evaluation survey by intervention players and coaches.ResultsIn total, 52 players (n = 31 intervention; n = 21 control) completed the study. Mixed-model analysis of variance (ANOVA) revealed significant differences in neck strength variables (p < 0.001), peak linear acceleration (p = 0.04) and peak angular velocity (p = 0.04) between the intervention and control groups over time. Intervention players demonstrated increases in mean composite neck strength (53.8% intervention vs 15.6% control) as well as decreases in mean peak linear head acceleration during heading (− 11.8% vs − 5.0%) from baseline to follow-up. Reduction in peak angular velocity was more pronounced in girls (− 27.7%) than boys (− 11.5%) in the intervention group. The addition of neck exercises into part 2 of the FIFA 11 + was feasible and accepted by players and coaches.ConclusionOn average, players who completed neck exercises demonstrated an increase in isometric neck strength and a decrease in head impact magnitude during heading. These exercises were easily incorporated into usual training.Australian New Zealand Clinical Trials Registry (no: ACTRN12619001375145).Supplementary InformationThe online version contains supplementary material available at 10.1007/s40279-021-01564-0.

NOS-dependent effects of plantar mechanical stimulation on mechanical characteristics and cytoskeletal proteins in rat soleus muscle during hindlimb suspension.

The study was aimed at investigating the mechanisms and structures which determine mechanical properties of skeletal muscles under gravitational unloading and plantar mechanical stimulation (PMS). We hypothesized that PMS would increase NO production and prevent an unloading-induced reduction in skeletal muscle passive stiffness. Wistar rats were hindlimb suspended and subjected to a daily PMS and one group of stimulated animals was also treated with nitric oxide synthase (NOS) inhibitor (L-NAME). Animals received mechanical stimulation of the feet for 4h a day throughout 7-day hindlimb suspension (HS) according to a scheme that mimics the normal walking of the animal. Seven-day HS led to a significant reduction in soleus muscle weight by 25%. However, PMS did not prevent the atrophic effect induced by HS. Gravitational unloading led to a significant decrease in maximum isometric force and passive stiffness by 38% and 31%, respectively. The use of PMS prevented a decrease in the maximum isometric strength of the soleus muscle. At the same time, the passive stiffness of the soleus in the PMS group significantly exceeded the control values by 40%. L-NAME (NOS inhibitor) administration attenuated the effect of PMS on passive stiffness and maximum force of the soleus muscle. The content of the studied cytoskeletal proteins (α-actinin-2, α-actinin-3, desmin, titin, nebulin) decreased after 7-day HS, but this decrease was successfully prevented by PMS in a NOS-dependent manner. We also observed significant decreases in mRNA expression levels of α-actinin-2, desmin, and titin after HS, which was prevented by PMS. The study also revealed a significant NOS-dependent effect of PMS on the content of collagen-1a, but not collagen-3a. Thus, PMS during mechanical unloading is able to maintain soleus muscle passive tension and force as well as mRNA transcription and protein contents of cytoskeletal proteins in a NOS-dependent manner.

Effects of Consecutive Matches on Isometric Hamstring Strength, Flexibility Values and Neuromuscular Performance in Female Field Hockey Players. A Prospective, Observational Study

This study aimed to analyze the effects of match congestion in a short period on isometric hamstring strength and hip/ankle range of motion in female field hockey players. Fourteen professional female field hockey players (age: 20.0 ± 5.4 years) played two consecutive hockey matches in 24 h and maximal isometric hamstring strength and hip and ankle range of motion were obtained before and after the first match, after the second match, and 48 h after the second match. Furthermore, locomotion patterns and ratings of perceived exertion were recorded during hockey competitions. Isometric knee flexion strength showed significantly higher values 48 h after the second match for the non-dominant limb (p ≤ 0.005, ηp2 = 0.19), while no differences were reported in the dominant limb (p = 0.370, ηp2 = 0.05). In addition, no differences were reported in the range-of-motion (ROM) variables such as the straight leg raise test or ankle dorsiflexion test (p = 0.075–0.217, ηp2 = 0.01–0.03). The countermovement jump height steadily increased over the matches except between post-match 2 and 48 h after post-match 2 (p &lt; 0.001, η2 = 0.382). Two consecutive official league field hockey matches played within 24 h did not have a negative effect on lower-limb risk factors (strength, hip and ankle ranges of motion, and ratings of perceived exertion) in female field hockey players directly, but they improved 48 h after the matches. This could indicate that 48 h recovery period following matches might be ideal for female field hockey players.