Optimal load for the muscle power profile of prone bench pull in Brazilian Jiu-Jitsu athletes

Background

No studies were observed optimal intensity loads for the muscle power performance during prone bench pull exercise in Brazilian Jiu-Jitsu athletes (BJJ) and this exercise is more similar with grip technics.

Purpose

To identify the optimal intensity for the muscle power performance variables during PBP exercise in BJJ athletes.

Methods

Fifteen athletes (25.5 ± 4.9 years; 65.6 ± 12.2 kg; 177.5 ± 4.7 cm) performed PBP at 30, 40, 50 and 60% of one repetition maximum (1RM) in a random order. The mean power (MP), mean velocity (MV), mean propulsive power (MPP) and mean propulsive velocity (MPV) were determined by measuring the barbell displacement by a linear encoder.

Results

In all power performance variables, higher power output was observed at 40 and 50% 1RM when compared to 30 and 60% 1RM (MP: F = 29.07; p < 0.001; MV: F = 40.80; p < 0.001; MPP: F = 53.69; p = 0.003; MPV: F = 166.2; p > 0.001). Additionally, it was observed higher MPP at 50% 1RM when compared to 40% 1RM (F = 55.23; p < 0.001). The polynomial adjustment indicated that the optimal intensity load for producing highest power performance ranged from 45 to 50% 1RM (R ² = 0.938–0.989) across all variables.

Conclusion

The loads between 45 and 50% 1RM produced the optimal muscle power performance during PBP exercise in BJJ athletes.

     

Health-related body composition and muscle strength in Brazilian Jiu-Jitsu practitioners

Purpose

This study aimed to analyze the health-related body composition and muscle strength performance in male and female Brazilian Jiu-Jitsu (BJJ) practitioners and to verify the upper and lower limbs bilateral asymmetry in these individuals.

Methods

Forty-three BJJ practitioners participated of this study, 20 men and 23 women. The individuals performed anthropometric measurements (body mass, height and body fat), neuromuscular lower limb assessments (countermovement jump—CMJ, squat jump—SJ and sit-and-reach test), and upper limb assessments (handgrip strength test—HGS test and Kimono Grip Strength Test—KGST).

Results

The main results demonstrated that most practitioners (both men and women) were classified as normal body fat, regular performance in CMJ and HGS, however, with poor flexibility. Higher performance in neuromuscular tests (CMJ, SJ and HGS) and KGST was reported in men compared to women, while women presented better flexibility and the use of elastic energy during the jump compared to men (p?<?0.05). Additionally, higher values of HGS in the dominant hand than the non-dominant was observed only in women (p?=?0.001), and no significant difference was observed in the unilateral CMJ between the limbs for both women (p?=?0.29) and men (p?=?0.06).

Conclusion

The recreational BJJ practice seems to induce improvements in body composition and muscle strength in the upper and lower limbs, without provoking bilateral asymmetries in the lower limbs. Men presented higher physical performance than women in most neuromuscular tests, but both showed poor flexibility.

     

Neuromuscular response differences to power vs strength back squat exercise in elite athletes

The study's aim was to establish the neuromuscular responses in elite athletes during and following maximal ‘explosive’ regular back squat exercise at heavy, moderate, and light loads. Ten elite track and field athletes completed 10 sets of five maximal squat repetitions on three separate days. Knee extension maximal isometric voluntary contraction (MIVC), rate of force development (RFD) and evoked peak twitch force (Pt) assessments were made pre‐ and post‐session. Surface electromyography [root mean square (RMS)] and mechanical measurements were recorded during repetitions. The heavy session resulted in the greatest repetition impulse in comparison to moderate and light sessions (P < 0.001), while the latter showed highest repetition power (P < 0.001). MIVC, RFD, and Pt were significantly reduced post‐session (P < 0.01), with greatest reduction observed after the heavy, followed by the moderate and light sessions accordingly. Power significantly reduced during the heavy session only (P < 0.001), and greater increases in RMS occurred during heavy session (P < 0.001), followed by moderate, with no change during light session. In conclusion, this study has shown in elite athletes that the moderate load is optimal for providing a neuromuscular stimulus but with limited fatigue. This type of intervention could be potentially used in the development of both strength and power in elite athletic populations.     

Disability,kinesiophobia, perceived stress,and pain are not associated with trunk muscle strength or aerobic capacity in chronic nonspecific low back pain

ObjectivesTo investigate to which extent disability, psychological and pain-related factors are associated with the outcomes of an isometric trunk muscle strength test and a cardiopulmonary exercise test in persons with chronic nonspecific low back pain (CNSLBP).DesignCross-sectional study.SettingREVAL Rehabilitation Research Center (Hasselt, Belgium).ParticipantsPersons with CNSLBP.Main outcome measuresQuestionnaires concerning disability, patient specific functioning, kinesiophobia, perceived stress, pain intensity, and central sensitization were recorded. Outcomes of an isometric trunk strength test (maximum back and abdominal torque) and cardiopulmonary exercise test (VO₂max) were assessed. Multivariate linear regression models determined factors explaining outcome variance.ResultsData of 101 persons (39 males, mean age: 44.2y (SD = 9.6)) was assessed. Neither disability, nor psychological, nor pain-related factors were associated with the assessments. Variance in back muscle strength (R² = 0.44, F = p < 0.01), abdominal muscle strength (R² = 0.68, F = p < 0.01), and aerobic capacity (R² = 0.76, F = p < 0.01) could only be explained through the included demographics covariates (age, gender, weight).ConclusionThis study highlighted the lack of biopsychosocial factors in explaining variance in outcomes of abdominal and back strength, and aerobic capacity in persons with CNSLBP with characteristics as depicted in the current sample. This information supports the valid interpretation of the outcomes of these assessments.     

Mobility and muscle strength in male former elite endurance and power athletes aged 66−91 years

The aim of this cross‐sectional study was to compare mobility and muscle strength in male former elite endurance and power athletes aged 66?91 years (n = 150; 50 men in both former elite athlete groups and in their control group). Agility, dynamic balance, walking speed, chair stand, self‐rated balance confidence (ABC‐scale), jumping height, and handgrip strength were assessed. Former elite power athletes had better agility performance time than the controls (age‐ and body mass index, BMI‐adjusted mean difference ?3.6 s; 95% CI ?6.3, ?0.8). Adjustment for current leisure time physical activity (LTPA) and prevalence of diseases made this difference non‐significant (P = 0.214). The subjects in the power sports group jumped higher than the men in the control group (age‐ and BMI‐adjusted mean differences for vertical squat jump, VSJ 4.4 cm; 95% CI 2.0, 6.8; for countermovement jump, CMJ 4.0 cm; 95% CI 1.7, 6.4). Taking current LTPA and chronic diseases for adjusting process did not improve explorative power of the model. No significant differences between the groups were found in the performances evaluating dynamic balance, walking speed, chair stand, ABC‐scale, or handgrip strength. In conclusion, power athletes among the aged former elite sportsmen had greater explosive force production in their lower extremities than the men in the control group.     

Muscular strength across the life course: The tracking and trajectory patterns of muscular strength between childhood and mid-adulthood in an Australian cohort

ObjectivesLow muscular strength is a risk factor for current and future adverse health outcomes. However, whether levels of muscular strength persist, or track, and if there are distinct muscular strength trajectories across the life course is unclear. This study aimed to explore muscular strength trajectories between childhood and mid-adulthood.DesignProspective longitudinal study.MethodsChildhood Determinants of Adult Health Study participants had their muscular strength (right and left handgrip, shoulder extension and flexion, and leg strength measured by hand-held, shoulder and leg-back dynamometers, and a combined strength score) assessed in childhood, young adulthood and mid-adulthood. The tracking of muscular strength was quantified between childhood and mid-adulthood (n = 385) and young- and mid-adulthood (n = 822). Muscular strength trajectory patterns were identified for participants who had their muscular strength assessed at least twice across the life course (n = 1280).ResultsLevels of muscular strength were persistent between childhood and mid-adulthood and between young- and mid-adulthood, with the highest tracking correlations observed for the combined strength score (childhood to mid-adulthood: r = 0.47, p < 0.001; young- to mid-adulthood: r = 0.72, p < 0.001). Three trajectories of combined muscular strength were identified across the life course; participants maintained average, above average, or below average levels of combined muscular strength.ConclusionsWeak children are likely to become weak adults in midlife unless strategies aimed at increasing muscular strength levels are introduced. Whether interventions aimed at increasing muscular strength could be implemented in childhood to help establish favourable muscular strength trajectories across the life course and in turn, better future health, warrant further attention.     

Longitudinal associations among cardiorespiratory and muscular fitness,motor competence and objectively measured physical activity

ObjectivesThis study aimed to investigate cross-lagged associations in motor competence, cardiorespiratory fitness, muscular fitness and accelerometer-based moderate-to-vigorous physical activity (MVPA) engagement.DesignOne-year prospective follow-up study.MethodsA sample was 491 (275 girls; M at baseline = 11.27, SD = .32) Finnish physical education students. Students’ motor competence was assessed by (1) two-legged jumping from side to side test, (2) throwing-catching combination test and (3) 5-leaps test. Their cardiorespiratory fitness was analyzed by a 20-m shuttle run test and muscular fitness by curl-up and push-up tests. Additionally, students’ MVPA was measured objectively by hip-worn accelerometers.ResultsResults demonstrated that: (1) cardiorespiratory fitness measured at Grade 5 was the only significant predictor of later MVPA and this association appeared only in the boys’ group, (2) MVPA assessed at Grade 5 significantly predicted cardiorespiratory fitness in the girls’ group, (3) cardiorespiratory fitness collected at Grade 5 associated with muscular fitness, locomotor and stability skills in both girls and boys, and (4) locomotor skills measured at Grade 5 predicted significantly muscular fitness, locomotor and manipulative skills in both sex groups.ConclusionsElementary school years are important in providing students with experiences in physical activity (PA) which leads to improvements s in cardiorespiratory health. Additionally, this study showed that cardiorespiratory fitness collected at Grade 5 associated with later muscular fitness, and locomotor and stability skills in both sex groups. These findings are noteworthy because muscular fitness in youth has several health-related benefits and motor competence in childhood and adolescence has positive association with later PA engagement.     

Sonographic evaluations in elite college baseball athletes

This study compared the thickness of the biceps and supraspinatus tendons, the widths of the subacromial space in the frontal and scapular planes, and abnormal sonographic findings in the shoulders of injured, and uninjured elite college baseball athletes and healthy controls. This study recruited two groups of 42 and 12 athletes, with and without histories of shoulder injuries, respectively, as well as one control group of 16 college students who were matched for physical characteristics but not involved in sports. The results showed that the thickness of the biceps and supraspinatus tendons and the subacromial space widths at 0 degrees and 90 degrees shoulder abduction in the frontal plane were significantly greater in the athletes than in the controls (P-values <0.004). The occurrences of the acromioclavicular joint bulging, bicep tendon degeneration, infraspinatus tendon degeneration and infraspinatus cortical irregularity differ significantly between the injured athlete and the group of uninjured athletes and controls (P-values <0.05). However, only infraspinatus tendon degeneration corresponded to the injury histories. There was a high similarity of sonographic spectrum of abnormal findings among the groups. Longitudinal follow-ups are required to determine the clinical importance of the sonographic spectrums and the occurrences of abnormal finding in asymptomatic athletes' shoulders.     

Salzburg Skiing for the Elderly Study: influence of alpine skiing on aerobic capacity, strength, power, and balance

Alpine skiing is a recreational sport with high demands on the cardiovascular and neuromuscular systems. It is assumed that skiing could have positive effects on the decline in aerobic capacity, strength, and balance ability of older individuals. In a 12-week intervention study, 47 elderly subjects (age 60-76 years) were randomized into an intervention group (IG) and a control group (CG). The IG averaged 28.5 days of guided skiing during 12 weeks. Aerobic capacity, leg power, and strength as well as postural stability were tested before, immediately after, and 10 weeks after the intervention phase. VO(2 max) improved by 7.2% from Pre to Post for the IG, without any change in the CG. Jump height increased on average by 6% over the 12 weeks for the IG, while jump height for the CG deteriorated by -11.7%. Dynamic maximal strength measured in both legs increased by 16% in the IG during the 12 weeks of skiing. In the CG, it increased by 7%, without being significant. In postural ability, no differences between groups or over time were noted. It appears that, in older individuals, 12 weeks of skiing leads to a significant increase in aerobic capacity, leg muscle power, and strength.     

Maximal aerobic power, lactate threshold, and running performance in master athletes

PURPOSE: This study sought to determine how lactate threshold (LT) is related to running performance in older male and female runners, if LT changes significantly with age, and if gender alters the relationship between LT and performance in older runners. METHODS: Subjects were 168 master runners (111 men, 57 women) selected from a longitudinal study, who ran at least 10 miles x wk(-1) for 5 yr or more. VO2max was measured on a treadmill and body composition by hydrostatic weighing. Blood samples taken each minute of exercise were analyzed for lactate concentration and LT determined as the breakpoint in lactate accumulation. Performance times and training histories were self-reported by questionnaire. RESULTS: Men had significantly greater body mass, fat-free mass (FFM), and VO2max (L x min(-1); mL x kg(-1) x min(-1)) than women. FFM and VO2max (L x min(-1); mL x kg(-1) x min(-1)) declined with age in both men and women. Running performance was significantly different between men and women and declined with age in both. LT (L x min(-1); mL x kg(-1) x min(-1)) was significantly different between men and women, and declined significantly with age in men, whereas LT (%VO2max) did not differ between men and women and increased significantly with age in both. VO2max (mL x kg(-1) x min(-1)) was the most significant predictor of performance in both men and women, whereas LT (L x min(-1)) added to the prediction of 5-km and 10-km performance in women. CONCLUSION: The results of this study demonstrate that VO2max (mL x kg(-1) x min(-1)) is a better predictor of performance than LT in older male and female runners. Additionally, LT as a percentage of VO2max increases significantly with age.     

Development of tables for classifying judo athletes according to maximal isometric strength and muscular power,and comparisons between athletes at different competitive levels

The objectives of this study were to develop normative tables to classify judo athletes by maximal isometric strength and muscular power, and to compare performance at different competitive levels. 102 male athletes performed tests of maximal isometric handgrip strength (MIHS), scapular humeral traction (MISHT), lumbar traction (MILT), lower body traction (MILBT), plyometric push-up (PPU), countermovement jump (CJ) and squat jump (SJ). Performance was classified as: ≤ 10th percentile?=?very poor, 11–25th percentile?=?poor, 26–75th percentile?=?regular, 76–90th percentile?=?good and >?90th percentile?=?excellent. Classification relative to body mass [isometric (kg/kg) and power (cm kg)] was as follows: MIHS—very poor: ≤ 0.81; poor: 0.82–0.96; regular: 0.97–1.51; good: 1.52–1.79; excellent: ≥ 1.80, MILT—very poor: ≤ 1.14; poor: 1.15–1.41; regular: 1.41–2.0; good: 2.0–2.5; excellent: ≥ 2.6, MILBT—very poor: ≤ 1.15; poor: 1.16–1.44; regular: 1.45–2.15; good: 2.16–2.62; excellent: ≥ 2.63, MISHT—very poor: ≤ 0.34; poor: 0.35–0.41; regular: 0.42–0.62; good: 0.63–0.73; excellent: ≥ 0.74, PPU—very poor: ≤ 635.4; poor: 635.5–901.9; regular: 902.0–1801.4; good: 1801.5–2369.7; excellent: ≥ 2369.8, SJ—very poor: ≤ 1690.7; poor: 1690.8–1990.3; regular: 1990.4–3387.9; good: 3388.0–4029.4; excellent: ≥ 4029.5 and CJ—very-poor: ≤ 1775.4; poor: 1775.5–2195.4; regular: 2195.5–3667.2; good: 3667.3–4208.3; excellent: ≥ 4208.4. State athletes had lower MISHT (p?=?0.015) than international athletes and lower CJ than national athletes (p?=?0.05). International athletes showed better PPU performance than others (p?<?0.05). MIHS, MISHT and PPU were sensitive to identify differences between competitive level of judo athletes (state, national and international level).     

The relationship between relative aerobic load,energy cost,and speed of walking in individuals post-stroke

BackgroundIndividuals post-stroke walk slower than their able-bodied peers, which limits participation. This might be attributed to neurological impairments, but could also be caused by a mismatch between aerobic capacity and aerobic load of walking leading to an unsustainable relative aerobic load at most economic speed and preference for a lower walking speed.Research questionWhat is the impact of aerobic capacity and aerobic load of walking on walking ability post-stroke?MethodsForty individuals post-stroke (more impaired N = 21; preferred walking speed (PWS)<0.8 m/s, less impaired N = 19), and 15 able-bodied individuals performed five, 5-minute treadmill walking trials at 70 %, 85 %, 100 %, 115 % and 130 % PWS. Energy expenditure (mlO₂/kg/min) and energy cost (mlO₂/kg/m) were derived from oxygen uptake (${\dot{\text{V}}\text{O}}_2$). Relative load was defined as energy expenditure divided by peak aerobic capacity (%${\dot{\text{V}}\text{O}}_2$peak) and by ${\dot{\text{V}}\text{O}}_2$ at ventilatory threshold (%${\dot{\text{V}}\text{O}}_2$-VT). Relative load and energy cost at PWS were compared with one-way ANOVA’s. The effect of speed on these parameters was modeled with Generalized Estimating Equations.ResultsBoth more and less impaired individuals post-stroke showed lower PWS than able-bodied controls (0.44 [0.19−0.76] and 1.04 [0.81−1.43] vs 1.36 [0.89−1.53] m/s) and higher relative load at PWS (50.2 ± 14.4 and 51.7 ± 16.8 vs 36.2 ± 7.6 %${\dot{\text{V}}\text{O}}_2$peak and 101.9 ± 20.5 and 97.0 ± 27.3 vs 64.9 ± 13.8 %${\dot{\text{V}}\text{O}}_2$-VT). Energy cost at PWS of more impaired (0.30 [.19–1.03] mlO₂/kg/m) was higher than less-impaired (0.19[0.10−0.24] mlO₂/kg/m) and able-bodied (0.15 [0.13−0.18] mlO₂/kg/m). For post-stroke individuals, increasing walking speed above PWS decreased energy cost, but resulted in a relative load above endurance threshold.SignificanceIndividuals post-stroke seem to reduce walking speed to prevent unsustainably high relative aerobic loads at the expense of reduced economy. When aiming to improve walking ability post-stroke, it is important to consider training aerobic capacity.     

Lower limb strength and flexibility in athletes with and without patellar tendinopathy

ObjectivesTo compare the hip, knee and ankle torques, as well as knee and ankle flexibility between athletes with patellar tendinopathy and asymptomatic controls.DesignCross-sectional study.SettingLaboratory setting.ParticipantsFourteen male volleyball, basketball or handball athletes, divided into 2 groups, patellar tendinopathy group (TG; n = 7) and asymptomatic control group (CG; n = 7).Main outcome measuresHip, knee and ankle isometric torques were measured with a handheld dynamometer. Weight-bearing ankle dorsiflexion, hamstring and quadriceps flexibility were measured with a gravity inclinometer.ResultsThe TG had 27% lower hip extensor torque when compared to the CG (P = 0.031), with no group differences in knee and ankle torques (P > 0.05). Also, the TG had smaller weight-bearing ankle dorsiflexion (P = 0.038) and hamstring flexibility (P = 0.006) when compared to the CG. Regarding quadriceps flexibility, no group differences were found (P = 0.828).ConclusionsStrength and flexibility deficits might contribute to a greater overload on the knee extensor mechanism, possibly contributing to the origin/perpetuation of patellar tendinopathy. Interventions aiming at increasing hip extensors strength as well as ankle and knee flexibility might be important for the rehabilitation of athletes with patellar tendinopathy.     

Evaluation of methods for normalizing muscle strength in elite and young athletes

BACKGROUND: The following equation has been most often used in order to present recorded muscle strength (F) normalised for various measures of body size (such as body mass m) Fnor = F x m(-b). Since previous studies have provided inconsistent results, the purpose of the present one was to assess the value of the exponential parameter b (b-value) that (a) provides both the normalised strength independent of body mass and (b) demonstrates the highest possible correlation between the normalised strength and standard tests of movement performance. METHODS: Thirteen groups of male and female athletes of both different age and different sport specialisation were tested for maximal isometric force of various leg muscle groups, as well as for vertical and standing long jump. RESULTS: The data obtained on most of the experimental groups suggested that the b-value close to the theoretically predicted b=0.67, but also different from b=0 and b=1, should be used for calculation of the normalised strength independent of body mass. Although the strength normalised using b=0.67 and b=1 demonstrated higher correlation with jumping performance than the non-normalised strength (i.e., b=0), the data also suggested that b>1 could provide the highest prediction of movement performance. CONCLUSIONS: Muscle strength should be calculated as force per kg(2/3) rather than as absolute force or force calculated per kg of body mass in order to assess strength independent of body size in routine testing of muscle function. However, different and probably task specific normalisation methods could be required in order to predict performance of various movement tasks by assessed muscle strength.     

Differential reflex adaptations following sensorimotor and strength training in young elite athletes

In young elite athletes the influence of a sensorimotor training (SMT = balance training) on strength, jump height and spinal reflex excitability was compared with adaptations induced by strength training (ST). Seventeen athletes were randomly assigned to either a SMT or a ST group. Before and after 6 weeks of training, maximal isometric strength (MVC) and rate of force development (RFD (max)) were determined. Changes in jump height and EMG activity were assessed during squat- (SJ), countermovement- (CMJ) and drop-jump (DJ). To evaluate neural adaptations, H-reflex recruitment was recorded at rest and during dynamic activation of the plantarflexors following stance perturbation. MVC was enhanced after ST but not influenced by SMT. RFD (max) was not affected by any training. Both SMT and ST significantly improved jump performance in SJ, CMJ, and DJ. Maximum H-reflex to maximum M-wave ratios (H (max)/M (max)-ratios) at rest remained unchanged. During stance perturbation, H (max)/M (max)-ratios were significantly reduced following SMT whereas ST augmented H (max)/M (max)-ratios (p < 0.05). In contrast to other studies, no changes in RFD were found. This may be explained by methodological and/or training specific differences. However, both SMT and ST improved jump performance in well trained young athletes but induced opposing adaptations of the H (max)/M (max)-ratio when measured during dynamic contractions. These adaptations were task-specific as indicated by the unchanged reflexes at rest. Decreased spinal excitability following SMT was interpreted as the attempt to improve movement control, whereas augmented excitability following ST accounts for the effort to enhance motoneuron output. Functionally, our results emphasise that SMT is not only beneficial for prevention and rehabilitation but also improves athletic performance.     

Susceptibility to infections in elite athletes: the S-curve

The susceptibility to upper respiratory tract infections (URTIs) after physical exercise has been described with a J-shaped curve, suggesting protection from infections with moderate exercise and increased risk for URTI's in elite athletes. Several factors such as time of inoculation, previous infections, pathogen exposure, other stressors than exercise etc. can influence infection outcome. Observed infections in athletes can, therefore, be either the result of increased susceptibility to a novel pathogen, or more severe symptoms of an already established infection. Moreover, the definitions of "strenuous" exercise and "elite" athletes are equivocal, making comparisons between studies difficult. Because absence of infections is inevitable to become and maintain status as an elite athlete, it is suggested that there is an S-shaped relationship between exercise load and risk of infections. To become an elite athlete one has to possess state-of-the-art physique, including an immune system able to withstand infections even during severe physiological and psychological stress.     

Lower-extremity isokinetic strength ratios of elite springboard and platform diving athletes

Objectives: The purpose of the present study was to examine knee extensor and flexor muscle strength ratios of an elite group of diving athletes.

Methods: Sixteen divers (10 females and 6 males) from the Brazil national team were assessed for lower-body strength. They had participated in international competitions such as the 2016 Olympic Games and 2015 Pan American Games. The dynamic concentric torque of their knee flexor and extensor muscles were evaluated using a Biodex isokinetic dynamometer. Bilateral tests were performed at 60º s^?1. Flexor to extensor (F/E) peak torque ratio and percentage bilateral difference (BD%) was also measured.

Results: The results revealed that elite diving athletes produced higher than usual reported in previous studies for relative knee extension torque (3.2 for females and 3.6 for males N?m?kg^?1). However, they presented low levels of knee flexor torque (1.5 for females and 1.8 for males N?m?kg^?1). These results are reflected in a low F/E ratio (0.39 to 0.49). Males presented a greater BD% in knee flexors when compared to females (12.4% vs 6.6%).

Conclusion: Elite diving athletes demonstrated high knee extensor and low knee flexor strength. This partially explains their low F/E ratio, which might increase risk of knee injuries. Strength and conditioning programs should strive to correct knee strength imbalances in diving athletes where necessary.