Maximal Rate Of Force Development Research Articles

Upper-Limb Muscle Fatigability in Para-Athletes Quantified as the Rate of Force Development in Rapid Contractions of Submaximal Amplitude.

This study aimed to compare neuromuscular fatigability of the elbow flexors and extensors between athletes with amputation (AMP) and athletes with spinal cord injury (SCI) for maximum voluntary force (MVF) and rate of force development (RFD). We recruited 20 para-athletes among those participating at two training camps (2022) for Italian Paralympic veterans. Ten athletes with SCI (two with tetraplegia and eight with paraplegia) were compared to 10 athletes with amputation (above the knee, N = 3; below the knee, N = 6; forearm, N = 1). We quantified MVF, RFD at 50, 100, and 150 ms, and maximal RFD (RFDpeak) of elbow flexors and extensors before and after an incremental arm cranking to voluntary fatigue. We also measured the RFD scaling factor (RFD-SF), which is the linear relationship between peak force and peak RFD quantified in a series of ballistic contractions of submaximal amplitude. SCI showed lower levels of MVF and RFD in both muscle groups (all p values ≤ 0.045). Despite this, the decrease in MVF (Cohen's d = 0.425, p < 0.001) and RFDpeak (d = 0.424, p = 0.003) after the incremental test did not show any difference between pathological conditions. Overall, RFD at 50 ms showed the greatest decrease (d = 0.741, p < 0.001), RFD at 100 ms showed a small decrease (d = 0.382, p = 0.020), and RFD at 150 ms did not decrease (p = 0.272). The RFD-SF decreased more in SCI than AMP (p < 0.0001). Muscle fatigability impacted not only maximal force expressions but also the quickness of ballistic contractions of submaximal amplitude, particularly in SCI. This may affect various sports and daily living activities of wheelchair users. Early RFD (i.e., ≤50 ms) was notably affected by muscle fatigability.

Acute effects of isotonic eccentric exercise on the neuromuscular function of knee extensors vary according to the motor task: impact on muscle strength profiles, proprioception and balance.

Eccentric exercise has often been reported to result in muscle damage, limiting the muscle potential to produce force. However, understanding whether these adverse consequences extend to a broader, functional level is of apparently less concern. In this study, we address this issue by investigating the acute and delayed effects of supramaximal isotonic eccentric exercise on neuromuscular function and motor performance of knee extensors during tasks involving a range of strength profiles, proprioception, and balance. Fifteen healthy volunteers (23.2 ± 2.9 years old) performed a unilateral isotonic eccentric exercise of the knee extensors of their dominant lower limb (4 × 10 reps at 120% of one Repetition Maximum (1RM)). The maximum voluntary isometric contraction (MVC), rate of force development (RFD), force steadiness of the knee extensors, as well as knee joint position sense and mediolateral (MLI) and anteroposterior stability (API) of the dominant lower limb, were measured pre-, immediately, and 24 h after the eccentric exercise. The EMG amplitude of the vastus medialis (VM) and biceps femoris (BF) were concomitantly evaluated. MVC decreased by 17.9% immediately after exercise (P < 0.001) and remained reduced by 13.6% 24 h following exercise (P < 0.001). Maximum RFD decreased by 20.4% immediately after exercise (P < 0.001) and remained reduced by 15.5% at 24 h (P < 0.001). During the MVC, EMG amplitude of the VM increased immediately after exercise while decreasing during the RFD task. Both values returned to baseline 24 h after exercise. Compared to baseline, force steadiness during submaximal isometric tasks reduced immediately after exercise, and it was accompanied by an increase in the EMG amplitude of the VM. MLI and knee joint position sense were impaired immediately after isotonic eccentric exercise (P < 0.05). While MLI returned to baseline values 24 h later, the absolute error in the knee repositioning task did not. Impairments in force production tasks, particularly during fast contractions and in the knee joint position sense, persisted 24 h after maximal isotonic eccentric training, revealing that neuromuscular functional outputs were affected by muscle fatigue and muscle damage. Conversely, force fluctuation and stability during the balance tasks were only affected by muscle fatigue since fully recovered was observed 24 h following isotonic eccentric exercise.

The rate of force relaxation scaling factor is highly sensitive to detect upper and lower extremity motor deficiencies in mildly affected people with multiple sclerosis.

The motor symptoms affecting upper and lower extremity functioning in people with multiple sclerosis (PwMS) are considered the cardinal symptoms of multiple sclerosis. There is still a need for outcome measures that can sensitively evaluate these symptoms. We aimed to investigate the sensitivity of the isometric outcomes (maximum force; Fmax, maximum rate of force development; RFDmax, rate of force development scaling factor; RFD-SF, and rate of force relaxation scaling factor; RFR-SF) and standard clinical tests (9-hole peg test; 9HPT and timed 25-feet walk test; T25FW) in detecting the upper and lower extremity motor deficiencies in PwMS and also in a subgroup of mildly affected PwMS whose performance in standard clinical tests were similar to controls. Twenty-nine PwMS (age: 47.9 (8.6) years, relapsing-remitting type, expanded disability status scale: 2.5 (1.5)) and their age- and gender-matched controls completed an identical testing protocol in the upper (grip force muscles) and lower (knee extensors) extremities. For each extremity, we assessed Fmax, RFDmax, RFD-SF, and RFR-SF. Additionally, participants completed standard clinical tests for the evaluation of upper- (9HPT) and lower-extremity (T25FW) function. Comparisons were made between controls and PwMS 1) using all study participants and 2) including only mildly affected PwMS whose performance in standard functional tests was comparable to controls. Independent sample t-tests were utilized to compare groups, with a p-value set at 0.01 to correct for multiple comparisons. P-values and effect sizes were used to evaluate the sensitivity of the outcome measures in detecting group differences. Our results indicate that most isometric outcomes and standard functional tests were sensitive in detecting motor deficiencies in both upper and lower extremities between groups (p<0.001). Among participants, 16 PwMS in 9HPT and 11 PwMS in T25FW demonstrated performance similar to that of the control group (9HPT: 18.85 (2.20) s vs 17.81 (2.19) s; p=0.19) and (T25FW: 3.60 (0.42) s vs 3.58 (0.29) s; p=0.92). The results of the comparisons between mildly affected PwMS and their controls indicate that RFR-SF is the only sensitive isometric outcome to detect differences between groups in the upper (-8.24 (0.76) 1/s vs -8.93 (0.6) 1/s; p=0.008) and lower extremity (-5.86 (1.13) 1/s vs -7.71 (1.11) 1/s; p<0.001). The rate of force relaxation scaling factor, which assesses the ability to rapidly relax muscle forces after quick contractions, demonstrates high sensitivity in detecting motor deficiencies in PwMS, even when the current standard clinical outcomes fail to detect these differences. Our findings emphasize the importance of future randomized controlled trials focusing on rehabilitative and therapeutic interventions that specifically target muscle force relaxation to enhance motor functioning in PwMS.

The profiles of single leg countermovement jump kinetics and sprinting in female soccer athletes

The purposes were to evaluate kinetics in lower limbs using single leg countermovement jump (SLCMJ) and to identify the differences in SLCMJ kinetics between sprinting fast players and sprinting slow players in elite university female soccer players. Seventeen participants at the national tournament level completed the survey. SLCMJ and 30 m sprinting tests were performed. A force-plate was used to collect the data of the SLCMJ test. Significant differences of concentric maximum rate of force development (RFD), concentric RFD, concentric RFD/body weight (BW), peak net takeoff force/BW, peak power, and peak power/BW existed between both legs during the SLCMJ among all the participants. For further analysis, the participants were divided into fast group and slow group based on sprinting performance. Significant differences existed between the two groups in concentric peak velocity (nondominant, p = 0.028) and vertical velocity at takeoff (nondominant, p = 0.021). Concentric maximum RFD (p = 0.036) was significantly different between both legs in the slow group. Among elite university female soccer players, the players who presented more increased asymmetry of kinetic characteristics of jumping, also showed weak sprinting performance. Moreover, the players presented the best performance in velocity of the jumping variables and also had the best sprinting performance. Coaches and players should focus on keeping inter-limb balance and developing jumping velocity to improve sports performance. In future, the cause-and-effect relationship between jumping and sprinting should be identified.

Neuromechanics of the Rate of Force Development.

The rate at which an individual can develop force during rapid voluntary contractions can be influenced by both the neural drive to a muscle and its intrinsic musculotendinous properties. We hypothesize that the maximal rate of force development across human individuals is mainly attributable to the rate of motor unit recruitment.

Dynamics Analysis of Different Types of Crouch Starts

&lt;p&gt;目的：近年來，物聯網 (Internet of Things, IOT) 的普及與人工智慧 (Artificial Intelligen)崛起，相關科技結合運動的跨領域合作越來越盛行，讓收集資料與分析資料變得更簡單也更有效率。本研究主要目的是運用物聯網技術開發起跑架來探討不同蹲踞式起跑動作之動力學分析。方法：受試者為 8名大學田徑隊短距離男子選手 (身高：173.16 &amp;plusmn; 4.77公分；體重：65.55 &amp;plusmn; 4.52公斤；年齡：20.06 &amp;plusmn; 1.09歲)，以一組物聯網系統與人工智慧演算法平臺，使用Arduino、Raspberry Pi與深度學習 (Deep Learning) 演算法開發一組適合平時訓練時所使用的田徑蹲踞式起跑訓練數據收集與分析系統 (專利編號：I632939)。在起跑架前、後踏板各安裝 20片壓力感測器 (取樣頻率1000 Hz) 。安裝前，每片壓力感測器都必須經校正程序，並利用多元線性回歸方程式，計算出其電壓-力量曲線斜率公式後再導入系統中。實驗數據以重複量數單因子變異數分析，比較起跑模式間的差異，若達到顯著差異，以 LSD法進行事後比較，顯著水準為 &amp;alpha; = .05。結果：在起跑出發階段，長式起跑後腳在最大反作用發生的時間與作用力均呈現比其它模式較佳的趨勢且踏板產生的初始發力率、最大發力率也較大，同時也發現受試者慣式起跑模式起跑線到前腳踏板間距過長的現象。結論：中式與長式起跑對整體起跑階段動力學參數有較佳的表現。建議選手未來可以在起跑出發階段方面，改變起跑架前踏板與起跑線的距離為 1.5個腳掌長，以利整體起跑出發表現。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Purpose: In recent years, with the popularity of the Internet of Things (IoT) and the rise of artificial intelligence (AI), the cross-disciplinary cooperation of related technologies combined with sports has become more and more popular, making it easier and more efficient to collect and analyze data. The purpose of this study is to do dynamics analysis of different types of crouch start by using starting blocks developed by IoT technology. Methods: The subjects were 8 short-distance male athletes from college track and field team (height: 173.16 &amp;plusmn; 4.77 cm; weight: 65.55 &amp;plusmn; 4.52 kg; age: 20.06 &amp;plusmn; 1.09 years old). A set of data collecting and analyzing system developed by IoT systems, AI algorithm platform, Arduino, Raspberry Pi, and Deep Learning was used to collect data (patent number: I632939). Each of front and rear block was installed 20 pressure sensors (sampling frequency 1000Hz), and before installation, each sensor was calibrated, and multiple linear regression was used to calculate the voltage-force curve slope formula and then import it into the system. The experimental data were analyzed by repeated-measures one-way ANOVA to compare the differences between the different crouch starts. If a significant difference was reached, the LSD method was used for post-hoc comparison, and the significant level was &amp;alpha; = .05. Results: In the starting phase, the rear foot of elongated staring mode was better than other modes in the time and force of maximal reaction force, and initial force and maximal rate of force development generated by the blocks were also larger. Also, it was also found that the distance from the starting line to front block was too long in subjects&amp;rsquo; habitual starting mode. Conclusions: The performance of dynamics analysis was better in the elongated and middle starting mode in the starting phase. It was suggested that athletes could adjust the front block 1.5-feet long from the staring line to improve starting performance.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Norm Values of Muscular Strength Across the Life Span in a Healthy Swiss Population: The COmPLETE Study.

Grip strength is used to estimate whole-body strength for health surveillance purposes. Explosive strength is considered important, yet economic measures able to detect early deterioration of neuromuscular capabilities are lacking. Whether handgrip maximum rate of force development (GRFD) or whole-body strength tests are better predictors of lower body power than handgrip maximum strength (GFmax) and their trajectories throughout the life span are unknown. GRFD should be more closely related to lower body power than GFmax, and its trajectories over the life span should more closely follow that of lower body power. Cross-sectional. Level 2b. A total of 613 healthy participants aged 20 to 91 years were tested for countermovement jump peak power, GFmax, handgrip rate of force development, and midthigh pull peak force (MTP). Cubic splines and linear models were built for age trajectories, generalized additive models for quintile curves, and linear regression was used to assess predictive quality. Peak power (Pmax) declined linearly to 60% of young adult level, with GRFD, GFmax, and MTP remaining stable up to age 50 years and then declining more sharply to 52% to 71% of young adult levels. Trajectories were similar for male and female participants. GRFD (β = 0.17) and MTP (β = 0.08) were worse predictors of Pmax than GFmax (β = 0.24) in models adjusted for age, sex, lean body mass, and vigorous physical activity levels. GRFD was not superior to maximum strength in predicting lower body power. For health surveillance purposes, it therefore appears that GFmax tests are more economical and equally good predictors of lower body explosive strength at older age. The data provided can be used as norm values for healthy subjects. Incorporating countermovement jump testing for early detection of declines in explosive capabilities might be advised.

Retropubic trocar modified with a load cell to verify contact with pubic bone

BackgroundVital injuries during midurethral sling surgery are avoided by maintaining constant trocar contact with bone, and yet this is challenging for a teaching surgeon to monitor during this blind procedure. We modified a retropubic trocar with a load cell to distinguish on-bone and off-bone movement and tested it on a midurethral sling surgery 3-dimensional surgery simulator. MethodsTwo experts and 3 novice surgeons performed retropubic trocar passage on the physical pelvic floor model using the modified trocar. Biofidelity was assessed comparing expert performance on a Thiel-embalmed cadaver and the physical model. The test-retest was assessed comparing performance on the physical pelvic model 2 weeks apart. The force variables were analyzed with paired and independent t tests. We performed post hoc analyses comparing the experts to novices on the physical model. ResultsThe root-mean-squared force was similar between the cadaver and model (24.3 vs 21.1 pounds, P = .62), suggesting biofidelity. Root-mean-squared force was also similar between the test and retest (14.0 vs 19.1 pounds, P =. 30). The expert surgeons exhibited a larger maximum force amplitude (51.2 vs 22.7 pounds, P = .03), shorter time to maximum force (2.7 vs 9.5 seconds, P = .03) and larger maximum rate of force development (171.5 vs 54.0 pounds/second, P = .01). ConclusionThis study suggested high test-retest reliability and adequate biofidelity of the modified trocar used on our midurethral sling surgery 3-dimensional surgery simulator. This innovative trocar can be used both in simulation and in the operating room to help the novice surgeons stay on the bone and to help the attending surgeon monitor safe surgery.

Deficits in rate of force production during multifinger tasks are associated with cognitive status.

ObjectivesThe multifinger force deficit (MFFD) is the decline in force generated by an individual finger as the number of fingers contributing to the action is increased. It has been proposed that as a measure of neural sufficiency rather than muscle status, it provides a means of detecting individuals at risk of cognitive decline. Age‐related deficits in central neural drive exert a disproportionate impact on the rate at which force can be generated. We examined whether a MFFD derived from the maximum rate at which force is generated, is more sensitive to individual differences in cognitive status, than one calculated using the maximum level of force.MethodsMonotonic associations between each of two variants of the MFFD, and cognition (measured with the Montreal Cognitive Assessment), were estimated cross sectionally using generalized partial rank correlations, in which age, level of education and degree of handedness were included as covariates. The participants (n=26) were community dwelling adults aged 66‐87.ResultsThe MFFD derived using the maximum rate of force development was negatively associated with cognitive status. The association for the MFFD based on the maximum level of force, was not statistically reliable. The associations with cognitive status obtained for both variants of the MFFD were of greater magnitude than those reported previously for standard grip strength dynamometry.ConclusionThe sensitivity with which the MFFD detects risk of cognitive decline may be enhanced by using the maximum rate of force developed by each finger, rather than the maximum force generated by each finger.

Isometric tests to evaluate upper and lower extremity functioning in people with multiple sclerosis: reliability and validity

BackgroundBoth upper and lower extremity motor symptoms are common in people with multiple sclerosis (PwMS) and there is a need to develop objective, reliable, and valid outcome measures. The aim of this study was to evaluate the reliability and external validity of the standard and novel isometric tests in the assessment of neuromuscular functioning in both upper (grip force; GF) and lower (knee extensors; KE) extremities in PwMS. MethodsTwenty-nine relapsing-remitting PwMS (Expanded Disability Status Scale (EDSS)<6) completed isometric and functional tests in upper (grip force) and lower (knee extension) extremity in two separate visits. Isometric testing included maximum force (maxF), maximum rate of force development (maxRFD), and our recently developed novel brief force pulse protocol (BFP). The dependent variables of BFP included rate of force development and relaxation scaling factors (RFD-SF and RFR-SF), which quantifies an individual's ability to scale the rates of force development and relaxation with the magnitude of force pulse produced. PwMS also completed functional tests of upper (9-hole peg (9HPT), finger tapping (FTT)) and lower extremity (25-ft walk test (T25WT), timed up and go (TUG), 5-time sit-to-stand (5StS), and Multiple Sclerosis Spasticity Scale (MSSS-88)). ResultsMost isometric outcome measures had high reliability (ICCs>0.87 and CVs<12%). In GF, both RFD-SF and RFR-SF had significant associations with 9HPT and FTT (r's between 0.49-0.55, p<0.05). In KE, while maxF, maxRFD, and RFD-SF were moderately correlated to some of the functional tests, the strongest correlations were observed for the RFR-SF (T25FW, r=0.71; TUG, r=0.60; 5StS, r=0.47; MSSS-88, r=0.60, and EDSS, r=0.71). Multiple linear regression analysis indicated that RFD-SF is the only predictor for 9HPT and RFR-SF is the only predictor of walking speed among the studied variables. ConclusionsBFP protocol provides highly reliable and relevant outcome measures to evaluate both upper and lower extremity functioning in PwMS. Specifically, the ability to relax muscle forces quickly after a quick force production highly contributes to walking speed in PwMS.

Collagen and Vitamin C Supplementation Increases Lower Limb Rate of Force Development.

Exercise and vitamin C-enriched collagen supplementation increase collagen synthesis, potentially increasing matrix density, stiffness, and force transfer. To determine whether vitamin C-enriched collagen (hydrolyzed collagen [HC] + C) supplementation improves rate of force development (RFD) alongside a strength training program. Using a double-blinded parallel design, over 3weeks, healthy male athletes (n = 50, 18-25years) were randomly assigned to the intervention (HC + C; 20g HC + 50mg vitamin C) or placebo (20g maltodextrin). Supplements were ingested daily 60min prior to training. Athletes completed the same targeted maximal muscle power training program. Maximal isometric squats, countermovement jumps, and squat jumps were performed on a force plate at the same time each testing day (baseline, Tests 1, 2, and 3) to measure RFD and maximal force development. Mixed-model analysis of variance compared performance variables across the study timeline, whereasttests were used to compare the change between baseline and Test 3. Over 3weeks, maximal RFD in the HC + C group returned to baseline, whereas the placebo group remained depressed (p = .18). While both groups showed a decrease in RFD through Test 2, only the treatment group recovered RFD to baseline by Test 3 (p = .036). In the HC + C group, change in countermovement jumps eccentric deceleration impulse (p = .008) and eccentric deceleration RFD (p = .04) wasimproved. A strong trend was observed for lower limb stiffness assessed in the countermovement jumps (p = .08). No difference was observed in maximal force or squat jump parameters. The HC + C supplementation improved RFD in the squat and countermovement jump alongside training.

Capsaicin and Its Effect on Exercise Performance, Fatigue and Inflammation after Exercise.

Capsaicin (CAP) activates the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons, improving ATP production, vascular function, fatigue resistance, and thus exercise performance. However, the underlying mechanisms of CAP-induced ergogenic effects and fatigue-resistance, remain elusive. To evaluate the potential anti-fatigue effects of CAP, 10 young healthy males performed constant-load cycling exercise time to exhaustion (TTE) trials (85% maximal work rate) after ingestion of placebo (PL; fiber) or CAP capsules in a blinded, counterbalanced, crossover design, while cardiorespiratory responses were monitored. Fatigue was assessed with the interpolated twitch technique, pre-post exercise, during isometric maximal voluntary contractions (MVC). No significant differences (p > 0.05) were detected in cardiorespiratory responses and self-reported fatigue (RPE scale) during the time trial or in TTE (375 ± 26 and 327 ± 36 s, respectively). CAP attenuated the reduction in potentiated twitch (PL: −52 ± 6 vs. CAP: −42 ± 11%, p = 0.037), and tended to attenuate the decline in maximal relaxation rate (PL: −47 ± 33 vs. CAP: −29 ± 68%, p = 0.057), but not maximal rate of force development, MVC, or voluntary muscle activation. Thus, CAP might attenuate neuromuscular fatigue through alterations in afferent signaling or neuromuscular relaxation kinetics, perhaps mediated via the sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation.

RELIABILITY OF SPECIFIC TESTS OF STRENGTH OF SPORTS ARM WRESTLING

The goal of the present study was to explore the reliability of a specific strength test of sports arm wrestling. The Maximal muscle force (Fmax) and maximal Rate of the muscle force development (RFDmax) for the right and left arm in a specific arm wrestling supinated and neutral position were analyzed. The sample of variables included the following two variables: Maximal voluntary force (F max ) and maximal voluntary explosive force, i.e., maximal Rate of force development (RFD max ), measured at the left (L) and right (R) arm (musculus Biceps Brachii), for both sports-specific positions – supination, and the neutral position. The Single variable Inter-test reliability was determined using the Intraclass Correlation Coefficient (ICC) and Cronbach's Alpha based on standardized items. The statistical significance level was determined on the criterion of p ≤ 0.05. Very high reliability (ICC = 0.916-0.971) exists for maximum muscle force variables, measured for the left and right arm with supinatorial and neutral hand positions. Moderate and high reliability (ICC = 0.681-0.892) was found for explosive muscle force variables, measured with the left and right hand in supinatorial and neutral hand positions. Generally, the highest values of muscle maximal and explosive force were achieved during the first test attempt. By looking at this information, coaches and athletes, may reliably use this specific AW test to create a clearer picture of the athlete's current physical readiness and for making appropriate decisions to guide the training process.

Maximal strength training-induced increase in efferent neural drive is not reflected in relative protein expression of SERCA

IntroductionMaximal strength training (MST), performed with heavy loads (~ 90% of one repetition maximum; 1RM) and few repetitions, yields large improvements in efferent neural drive, skeletal muscle force production, and skeletal muscle efficiency. However, it is elusive whether neural adaptations following such high intensity strength training may be accompanied by alterations in energy-demanding muscular factors.MethodsSixteen healthy young males (24 ± 4 years) were randomized to MST 3 times per week for 8 weeks (n = 8), or a control group (CG; n = 8). Measurements included 1RM and rate of force development (RFD), and evoked potentials recordings (V-wave and H-reflex normalized to M-wave (M) in the soleus muscle) applied to assess efferent neural drive to maximally contracting skeletal muscle. Biopsies were obtained from vastus lateralis and analyzed by western blots and real-time PCR to investigate the relative protein expression and mRNA expression of Sarcoplasmic Reticulum Ca2+ ATPase (SERCA) 1 and SERCA2.ResultsSignificant improvements in 1RM (17 ± 9%; p < 0.001) and early (0–100 ms), late (0–200 ms) and maximal RFD (31–53%; p < 0.01) were observed after MST, accompanied by increased maximal Vmax/Msup-ratio (9 ± 14%; p = 0.046), with no change in H-reflex to M-wave ratio. No changes were observed in the CG. No pre- to post-training differences were found in mRNA or protein expressions of SERCA1 and SERCA2 in either group.ConclusionMST increased efferent neural drive to maximally contracting skeletal muscle, causing improved force production. No change was observed in SERCA expression, indicating that responses to high intensity strength training may predominantly be governed by neural adaptations.

Different plantar flexors neuromuscular and mechanical characteristics depending on the preferred running form

Two main types of endurance runners have been identified: aerial runners (AER), who have a larger flight time, and terrestrial runners (TER), who have a longer ground contact time. The purpose of this study was to assess the neuromuscular characteristics of plantar flexors between AER and TER runners. Twenty-four well-trained runners participated in the experiment. They were classified either in a TER or AER group according to the Volodalen® scale. Plantar flexors’ maximal rate of force development (RFD) and maximal voluntary contraction force (MVC) were assessed. Percutaneous electrical stimulation was delivered to the posterior tibial nerve to evoke maximal M-waves and H-reflexes of the triceps surae muscles. These responses, as well as voluntary activation, muscle potentiation, and V-waves, were recorded by superimposing stimulations to MVCs. RFD was significantly higher in AER than in TER, while MVC remained unchanged. This was accompanied by higher myoelectrical activity recorded in the soleus muscle. While M-waves and other parameters remained unchanged, maximal H-reflex was significantly higher in AER than in TER, still in soleus only. The present study raised the possibility of different plantar flexors’ neuromuscular characteristics according to running profile. These differences seemed to be focused on the soleus rather than on the gastrocnemii.

Acute Capsaicin and Exercise Performance in Humans: Potential Neuromuscular Mechanisms

The pungent bioactive ingredient in peppers (Capsaicin; CAP) has been widely investigated for its activation of the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons. It has been shown to improve mitochondrial biogenesis, adenosine triphosphate (ATP) production and vascular function. In animal models has been demonstrated that increases exercise performance and decreases fatigue development. However, whether acute oral CAP improves endurance performance and the potential underlying mechanisms remains elusive. This study aimed to evaluate the potential ergogenic and anti-fatigue effects of acute oral CAP supplementation in healthy humans. In a double-blind, placebo-controlled, cross-over design, 10 young healthy males performed constant-load cycling exercise (294±55W; 85% of peak power output) to exhaustion, after acute ingestion of placebo (PL; 1000mg fiber pill) and CAP (780mg pill) capsules. Fatigue was assessed on the dominant quadriceps with the interpolated twitch technique, via changes in supramaximal electrical stimulation pre- vs. post-exercise, during isometric maximal voluntary contractions (MVC) and at rest. Cardiopulmonary parameters (heart rate, cardiac output, oxygen consumption, ventilation) were assessed throughout the exercise. No statistically significant differences were detected in the muscle contractile functions, despite a trend (P=0.07) for a decreased time to exhaustion during CAP (PL: 369±85 vs. CAP: 296±64 sec). All the values (except muscle voluntary activation (%VMA)) significantly decreased from pre- to post-exercise in both conditions. The exercise-induced attenuation of the intrinsic muscle contractile properties (Maximal rate of force development (MRFD) and Maximal relaxation rate (MRR) of the resting twitch force) were mitigated, in part, by CAP. Notably, in the PL condition MRR was seemingly reduced by 47±33%, while only of 29±68% in CAP; contrarily, MRFD decreased similarly of 47±23% and of 40±27% in PL and CAP, respectively. In 9 participants, the resting twitch (estimate of peripheral muscle fatigue) pre- vs. post-exercise decreased less with CAP (PL: 44±17 vs. CAP: 37±13%). CAP did not influence the MVC nor %VMA. The cardiopulmonary responses were similar between the conditions (P>0.05). In contrast to prior work, acute oral capsaicin did not improve endurance performance in the present study. CAP did elicit a tendency for faster relaxation rate, which might suggest an enhanced activation of the sarcoendoplasmic reticulum calcium ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation. However, this altered Ca2+ handling might also increase ATP demand. The tendency for CAP to attenuate the exercise-induced reduction in muscle function, or fatigue, might provide a mechanistic basis for the previously demonstrated beneficial effects of CAP. Further work is needed in larger samples, to further determine the optimal dosing and loading strategies, to better understand the potential ergogenic effects of capsaicin.

The acute effects of whole body vibration stimulus warm-up on skill-related physical capabilities in volleyball players

Whole body vibration (WBV) has been suggested to improve athletes’ neuromuscular strength and power. This study investigated the effect of single WBV stimulation on volleyball-specific performance. The participants were 20 elite male volleyball players who performed a 1-min warm-up exercise on a vibration platform at a frequency of 30 Hz and peak-to-peak displacement of 2 mm. After the warm-up exercise, the participants performed a blocking agility test (BAT), 10-m sprinting test, agility T-test, and counter movement jump test. We compared the participants’ performance at four time points (Pretest, Post 0, Post 1, and Post 2). The results revealed that the participants’ BAT performance and maximum rate of force development improved significantly 1 min after the vibration stimulation (p < 0.01). The WBV (frequency of 30-Hz, peak-to-peak displacement of 2 mm) intervention significantly improved the volleyball-specific defensive performance and speed strength of the participants. Accordingly, by undergoing WBV as a form of warm-up exercise, the technique and physical fitness of volleyball players can be improved.

RELIABILITY OF A SIMPLE NOVEL FIELD TEST FOR THE MEASUREMENT OF PLANTAR FLEXOR MUSCLE STRENGTH

ABSTRACT Introduction When a person is in a standing position, the plantar flexor muscles are involved in most static and dynamic body movements. Objectives The aim of this study was to investigate the trial to trial and factorial reliability of measuring the contractile characteristics of PF muscles using a simple novel field test. Methods The sample consisted of 452 healthy subjects, 120 male and 332 female. The research was conducted by means of the trial to trial testing method, using isometric dynamometry performed in field conditions. ANOVA was used to estimate the differences among the trials, Cronbach’s alpha and interclass correlation to estimate the correlations among the trials, and principal component analysis to evaluate the contribution of each trial to overall variability. Results The main findings of this study are that trials differed significantly (p&lt;0.000) for maximal force (Fmax) and maximal rate of force development (RFDmax), indicating that the three procedural trials were necessary. The trials were highly correlated (Fmax, RFDmax, r&gt;0.9), proving that measuring was reliable, and the factorial analysis separated the second and third trials, the second trial accounting for most of the total variability. Conclusions The simple novel field test for the measurement of plantar flexor contractile characteristics recommended by this study proved to be as highly reliable as laboratory testing, but was easy to perform in conditions outside of scientific or diagnostic institutions, which greatly facilitates the work of scientists, coaches and professionals. Level of Evidence II; Diagnostic Studies – Investigating a diagnostics test.

Surface Electromyography: What Limits Its Use in Exercise and Sport Physiology?

The aim of the present paper is to examine to what extent the application of surface electromyography (sEMG) in the field of exercise and, more in general, of human movement, is adopted by professionals on a regular basis. For this purpose, a brief history of the recent developments of modern sEMG techniques will be assessed and evaluated for a potential use in exercise physiology and clinical biomechanics. The idea is to understand what are the limitations that impede the translation of sEMG to applied fields such as exercise physiology. A cost/benefits evaluation will be drawn in order to understand possible causes that prevents sEMG from being routinely adopted. Among the possible causative factors, educational, economic and technical issues will be considered. Possible corrective interventions will be proposed. We will also give an overview of the parameters that can be extracted from the decomposition of the sHDEMG signals and how this can be related by professionals for assessing the health and disease of the neuromuscular system. We discuss how the decomposition of surface EMG signals might be adopted as a new non-invasive tool for assessing the status of the neuromuscular system. Recent evidences show that is possible to monitor the changes in neuromuscular function after training of longitudinally tracked populations of motoneurons, predict the maximal rate of force development by an individual via motoneuron interfacing, and identify possible causal relations between aging and the decrease in motor performance. These technologies will guide our understanding of motor control and provide a new window for the investigation of the underlying physiological processes determining force control, which is essential for the sport and exercise physiologist. We will also illustrate the challenges related to extraction of neuromuscular parameters from global EMG analysis (i.e., root-mean-square, and other global EMG metrics) and when the decomposition is needed. We posit that the main limitation in the application of sEMG techniques to the applied field is associated to problems in education and teaching, and that most of the novel technologies are not open source.

Relationship among the quality of cognitive abilities, depression symptoms, and various aspects of handgrip strength in the elderly

Background/Aim. Both the cognitive and physical functioning changes occur within the normal aging, suggesting possible common biological processes. The aging process is often characterized by a reduction of adaptive responses, an increasing vulnerability and functional limitations. The aim of this study was to determine if there were correlations between particular cognitive abilities (verbal ability, spatial ability, processing speed, memory, verbal fluency, divergent thinking, memory, attention, executive functions, conceptualization, orientation, computation), depression symptoms and different dynamometric parameters of muscle contraction, during handgrip (HG) of both hands, in the elderly population. Methods. The sample consisted of 98 participants, 16 males and 82 females, aged from 65 to 85. Neuropsychological assessment included Montreal Cognitive Assessment (MoCA), Frontal Function Test (Go/No-Go), Categorical and Phonemic fluency tests and Geriatric Depression Scale Short Form (GDS-SF). Physical measures were assessed by Handgrip Dynamometry Tests (HG), and included: the maximum force (Fmax), maximal rate of force development (RFDmax), static endurance HG time realized at 50% of maximal HG force (tFmax50%) of dominant (Do) and non-dominant (NDo) hand. Results. Higher MoCA score was followed by higher values of muscle endurance of dominant hands. Higher values of F max of dominant hand were associated with higher values of Alternating Trail Making that is by visuoconstructive abilities (MoCA). The variable Categorical fluency was in a small, positive correlation with Fmax. No correlation of depressive symptoms with HG parameters was found except in the subgroup of female subjects. Conclusion. Better cognitive performance was associated with better HG muscle strength. Therefore, HG strength can be a useful tool in geriatric practice in monitoring not only physical, but also cognitive function status and de-cline. The link between lower cognitive functioning and lower values of HG variables, emphasize the need for in-creased awareness about it in clinical practice.