The type II RAF inhibitor tovorafenib in relapsed/refractory pediatric low-grade glioma: the phase 2 FIREFLY-1 trial.

BRAF genomic alterations are the most common oncogenic drivers in pediatric low-grade glioma (pLGG). Arm 1 (n = 77) of the ongoing phase 2 FIREFLY-1 (PNOC026) trial investigated the efficacy of the oral, selective, central nervous system-penetrant, type II RAF inhibitor tovorafenib (420 mg m-2 once weekly; 600 mg maximum) in patients with BRAF-altered, relapsed/refractory pLGG. Arm 2 (n = 60) is an extension cohort, which provided treatment access for patients with RAF-altered pLGG after arm 1 closure. Based on independent review, according to Response Assessment in Neuro-Oncology High-Grade Glioma (RANO-HGG) criteria, the overall response rate (ORR) of 67% met the arm 1 prespecified primary endpoint; median duration of response (DOR) was 16.6 months; and median time to response (TTR) was 3.0 months (secondary endpoints). Other select arm 1 secondary endpoints included ORR, DOR and TTR as assessed by Response Assessment in Pediatric Neuro-Oncology Low-Grade Glioma (RAPNO) criteria and safety (assessed in all treated patients and the primary endpoint for arm 2, n = 137). The ORR according to RAPNO criteria (including minor responses) was 51%; median DOR was 13.8 months; and median TTR was 5.3 months. The most common treatment-related adverse events (TRAEs) were hair color changes (76%), elevated creatine phosphokinase (56%) and anemia (49%). Grade ≥3 TRAEs occurred in 42% of patients. Nine (7%) patients had TRAEs leading to discontinuation of tovorafenib. These data indicate that tovorafenib could be an effective therapy for BRAF-altered, relapsed/refractory pLGG. ClinicalTrials.gov registration: NCT04775485 .

Recombinant polio-rhinovirus immunotherapy for recurrent paediatric high-grade glioma: a phase 1b trial.

BACKGROUND: Outcomes of recurrent paediatric high-grade glioma are poor, with a median overall survival of less than 6 months. Viral immunotherapy, such as the polio-rhinovirus chimera lerapolturev, is a novel approach for treatment of recurrent paediatric high-grade glioma and has shown promise in adults with recurrent glioblastoma. The poliovirus receptor CD155 is ubiquitously expressed in malignant paediatric brain tumours and is a treatment target in paediatric high-grade glioma. We aimed to assess the safety of lerapolturev when administered as a single dose intracerebrally by convection enhanced delivery in children and young people with recurrent WHO grade 3 or grade 4 glioma, and to assess overall survival in these patients. METHODS: This phase 1b trial was done at the Duke University Medical Center (Durham, NC, USA). Patients aged 4-21 years with recurrent high-grade malignant glioma (anaplastic astrocytoma, glioblastoma, anaplastic oligoastrocytoma, anaplastic oligodendroglioma, or anaplastic pleomorphic xanthoastrocytoma) or anaplastic ependymoma, atypical teratoid rhabdoid tumour, or medulloblastoma with infusible disease were eligible for this study. A catheter was tunnelled beneath the scalp for a distance of at least 5 cm to aid in prevention of infection. The next day, lerapolturev at a dose of 5 × 107 median tissue culture infectious dose in 3 mL infusate loaded in a syringe was administered via a pump at a rate of 0·5 mL per h as a one-time dose. The infusion time was approximately 6·5 h to compensate for volume of the tubing. The primary endpoint was the proportion of patients with unacceptable toxic effects during the 14-day period after lerapolturev treatment. The study is registered with ClinicalTrials.gov, NCT03043391. FINDINGS: Between Dec 5, 2017, and May 12, 2021, 12 patients (11 unique patients) were enrolled in the trial. Eight patients were treated with lerapolturev. The median patient age was 16·5 years (IQR 11·0-18·0), five (63%) of eight patients were male and three (38%) were female, and six (75%) of eight patients were White and two (25%) were Black or African American. The median number of previous chemotherapeutic regimens was 3·50 (IQR 1·25-5·00). Six of eight patients had 26 treatment-related adverse events attributable to lerapolturev. There were no irreversible (ie, persisted longer than 2 weeks) treatment-related grade 4 adverse events or deaths. Treatment-related grade 3 adverse events included headaches in two patients and seizure in one patient. Four patients received low-dose bevacizumab on-study for treatment-related peritumoural inflammation or oedema, diagnosed by both clinical symptoms plus fluid-attenuated inversion recovery MRI. The median overall survival was 4·1 months (95% CI 1·2-10·1). One patient remains alive after 22 months. INTERPRETATION: Convection enhanced delivery of lerapolturev is safe enough in the treatment of recurrent paediatric high-grade glioma to proceed to the next phase of trial. FUNDING: Solving Kids Cancer, B+ Foundation, Musella Foundation, and National Institutes of Health.

Listening to paediatric primary care nurses: a qualitative study of the potential for interprofessional oral health practice in six federally qualified health centres in Massachusetts and Maryland.

OBJECTIVES: To explore the opportunities for interprofessional collaboration (IPC) to improve paediatric oral health in federally qualified health centres (FQHCs), to identify challenges to IPC-led integration of oral health prevention into the well-child visit and to suggest strategies to overcome barriers. SAMPLE: Nurse managers (NMs), nurse practitioners (NPs), paediatric clinical staff and administrators in six FQHCs in two states were interviewed using a semistructured format. DESIGN: Grounded theory research. Topics included feasibility of integration, perceived barriers and strategies for incorporating oral health into paediatric primary care. MEASUREMENTS: Qualitative data were coded and analysed using NVivo 10 to generate themes iteratively. RESULTS: Nurses in diverse roles recognised the importance of oral health prevention but were unaware of professional guidelines for incorporating oral health into paediatric encounters. They valued collaborative care, specifically internal communication, joint initiatives and training and partnering with dental schools or community dental practices. Barriers to IPC included inadequate training, few opportunities for cross-communication and absence of charting templates in electronic health records. CONCLUSIONS: NMs, NPs and paediatric nursing staff all value IPC to improve patients' oral health, yet are constrained by lack of oral health training and supportive charting and referral systems. With supports, they are willing to take on responsibility for introducing oral health preventive measures into the well-child visit, but will require IPC approaches to training and systems changes. IPC teams in the health centre setting can work together, if policy and administrative supports are in place, to provide oral health assessments, education, fluoride varnish application and dental referrals, decrease the prevalence of early childhood caries and increase access to a dental home for low-income children.

Integration of Oral Health Into the Well-Child Visit at Federally Qualified Health Centers: Study of 6 Clinics, August 2014-March 2015.

INTRODUCTION: Early childhood caries, the most common chronic childhood disease, affects primary dentition and can impair eating, sleeping, and school performance. The disease is most prevalent among vulnerable populations with limited access to pediatric dental services. These same children generally receive well-child care at federally qualified health centers. The objective of this study was to identify facilitators and barriers to the integration of oral health into pediatric primary care at health centers to improve problem recognition, delivery of preventive measures, and referral to a dentist. METHODS: We collected and analyzed background data and data from structured observations and 39 interviews with administrators and staff at 6 clinics in 2 states, Maryland and Massachusetts. RESULTS: Participants valued oral health across professional roles but cited limited time, lack of training and expertise, low caregiver literacy, and lack of shared medical and dental electronic records as barriers to cooperation. Facilitators included an upper-level administration with the vision to see the value of integration, designated team leaders, and champions. An administration's vision, not structural determinants, patient characteristics, or geographic location, predicted the level of integration. Interviewees generated multilevel recommendations to promote delivery of oral health preventive measures and services during a well-child visit. CONCLUSION: Poor oral health contributes to health care disparities. Barriers to integrating dental care into pediatric medical practice at health centers must be overcome to improve oral health for children living in poverty, with a disability, at a rural address, or any combination of these. Implementation will require adapting delivery systems to support multidisciplinary collaboration. Strategies suggested here may point the way to enhancing children's oral health.

Effects of short-term resistance training and subsequent detraining on the electromechanical delay.

INTRODUCTION: The purpose of this study was to examine and compare the effects of 3 days of dynamic constant external resistance (DCER) and isokinetic (ISOK) training and subsequent detraining on the electromechanical delay (EMD). METHODS: Thirty-one men [age 22.2 ± 4.2 years, body mass 77.9 ± 12.9 kg, height 173.9 ± 5.4 cm (mean ± SD)] were randomly assigned to a DCER training group, ISOK training group, or control (CONT) group. RESULTS: No significant changes were found for EMD from pre- to posttraining assessments 1, 2, and 3 [4.5 ± 0.2 ms, 4.7 ± 0.2 ms, 4.5 ± 0.1 ms, 4.5 ± 0.2 ms, respectively (mean ± SE)] (P > 0.05). CONCLUSIONS: It can be hypothesized that increases in strength observed after a short-term resistance training program may not be attributed to stiffness changes in the series-elastic component.

Consistency of rapid muscle force characteristics: influence of muscle contraction onset detection methodology.

The purpose of this study was to investigate the consistency of commonly reported rapid force characteristics utilizing both automated and manual muscle contraction onset detection methods. Twenty-four healthy volunteers performed isometric strength testing of the plantar flexor muscle group on two nonconsecutive days. Test-retest reliability was evaluated using intraclass correlation coefficients (ICCs), standard errors of measurement (SEM), and the SEM as a percentage of the mean (SEM%) for rate of force development (RFD), relative RFD, contractile impulse, and absolute force-time values at various epoch durations using automated and manual onset detection methods. For all rapid force variables, ICC and SEM% values ranged from 0.52 to 0.96 and 7.56% to 37.56%, respectively. For the majority of these variables (20 of 23), the automated onset detection method resulted in higher ICC and lower SEM% values compared to the manual onset detection method. Regardless of onset detection methodology, the consistency of relative RFD values declined following 50% of MVC. Collectively, these findings indicated that commonly evaluated rapid muscle force variables demonstrated acceptable relative and absolute consistency values. However, these values were generally superior for the automated onset detection methodology. Additionally, the consistency of relative RFD values declines following 50% MVC and therefore should be evaluated with caution.

Acute effects of passive stretching on the electromechanical delay and evoked twitch properties: a gender comparison.

This study examined the acute effects of passive stretching on electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and peak-to-peak M-wave (PPM) for the soleus muscle during evoked isometric plantar flexion muscle actions. Fourteen men (mean age ± SD = 21.2 ± 2.4 years; body mass = 80.0 ± 14.9 kg; height = 176.9 ± 7.2 cm) and 20 women (20.9 ± 2.5 years; 61.3 ± 8.9 kg; 165.3 ± 7.5 cm) volunteered for the study. Five single-square, supramaximal transcutaneous electrical stimuli (each separated by 5 s) were delivered to the tibial nerve before and after passive stretching. A time × gender interaction was observed for EMD, and the post hoc dependent-samples t tests indicated that EMD increased 4% for the women (p = .023), but not for the men (p = .191). There were no other stretching-related changes for PTF, RFD, or p-p M-wave for either the men or women (p > .05). These findings tentatively suggested that mechanical factors related to the stiffness of the muscle-tendon unit may contribute to the explanation for why stretching caused an acute increase in the EMD during evoked twitches in the women, but not in the men.

Percent voluntary inactivation and peak force predictions with the interpolated twitch technique in individuals with high ability of voluntary activation.

The purpose of this study was to examine the sensitivity and peak force prediction capability of the interpolated twitch technique (ITT) performed during submaximal and maximal voluntary contractions (MVCs) in subjects with the ability to maximally activate their plantar flexors. Twelve subjects performed two MVCs and nine submaximal contractions with the ITT method to calculate percent voluntary inactivation (%VI). Additionally, two MVCs were performed without the ITT. Polynomial models (linear, quadratic and cubic) were applied to the 10-90% VI and 40-90% VI versus force relationships to predict force. Peak force from the ITT MVC was 6.7% less than peak force from the MVC without the ITT. Fifty-eight percent of the 10-90% VI versus force relationships were best fit with nonlinear models; however, all 40-90% VI versus force relationships were best fit with linear models. Regardless of the polynomial model or the contraction intensities used to predict force, all models underestimated the actual force from 22% to 28%. There was low sensitivity of the ITT method at high contraction intensities and the predicted force from polynomial models significantly underestimated the actual force. Caution is warranted when interpreting the % VI at high contraction intensities and predicted peak force from submaximal contractions.

Differences in the log-transformed electromyographic-force relationships of the plantar flexors between high- and moderate-activated subjects.

The present study examined the log-transformed electromyographic amplitude (EMG) versus force relationships for the medial gastrocnemius (MG) and soleus (SOL) in high- and moderate-activated subjects. Twenty-five (age=21±2 year; mass=62±12 kg) participants performed six submaximal contractions (30-90% maximal voluntary contraction [MVC]) with the interpolated twitch technique (ITT) performed at 90% MVC to calculate percent voluntary activation (% VA). Sixteen participants with>90% VA at 90% MVC were categorized high-activated group; the remaining nine were the moderate-activated group. Linear regression models were fit to the log-transformed EMG-force relationships. The slope (b value) and the antilog of the Y-intercept (a value) were calculated. The b values from the MG EMG-force relationships were higher (P<0.05) for the high-activated group (1.27±0.13) than the moderate-activated group (0.88±0.06). The a values and p-p M-wave amplitude values (collapsed across twitches [superimposed and potentiated]) were larger (P<0.05) for the MG (1.17±0.40 and 8.98±0.46 mV) than the SOL (0.24±0.07 and 4.48±0.20 mV) when collapsed across groups. The b value from the log-transformed EMG-force relationships is an attractive model to determine if a subject has the ability to achieve high activation of their MG without muscle or nerve stimulation.

Effects of two modes of static stretching on muscle strength and stiffness.

PURPOSE: The purpose of the present study was to examine the effects of constant-angle (CA) and constant-torque (CT) stretching of the leg flexors on peak torque (PT), EMGRMS at PT, passive range of motion (PROM), passive torque (PAS(TQ)), and musculotendinous stiffness (MTS). METHODS: Seventeen healthy men (mean ± SD: age = 21.4 ± 2.4 yr) performed a PROM assessment and an isometric maximal voluntary contraction of the leg flexors at a knee joint angle of 80° below full leg extension before and after 8 min of CA and CT stretching. PASTQ and MTS were measured at three common joint angles for before and after assessments. RESULTS: PT decreased (mean ± SE = 5.63 ± 1.65 N·m) (P = 0.004), and EMG(RMS) was unchanged (P > 0.05) from before to after stretching for both treatments. PROM increased (5.00° ± 1.03°) and PASTQ decreased at all three angles before to after stretching (angle 1 = 5.03 ± 4.52 N·m, angle 2 = 6.30 ± 5.88 N·m, angle 3 = 6.68 ± 6.33 N·m) for both treatments (P ≤ 0.001). In addition, MTS decreased at all three angles (angle 1 = 0.23 ± 0.29 N·m·°(-1), angle 2 = 0.26 ± 0.35 N·m·°(-1), angle 3 = 0.28 ± 0.44 N·m·°(-1)) after the CT stretching treatment (P < 0.005); however, MTS was unchanged after CA stretching (P > 0.05). CONCLUSIONS: PT, EMG(RMS), PROM, and PASTQ changed in a similar manner after stretching treatments; however, only CT stretching resulted in a decrease in MTS. Therefore, if the primary goal of the stretching routine is to decrease MTS, these results suggest that CT stretching (constant pressure) may be more appropriate than a stretch held at a constant muscle length (CA stretching).

Mechanical scale and load cell underwater weighing: a comparison of simultaneous measurements and the reliability of methods.

Both load cell and mechanical scale-based hydrostatic weighing (HW) systems are used for the measurement of underwater weight. However, there has been no direct comparison of the 2 methods. The purpose of the current investigation was to simultaneously compare a load cell and mechanical scale for use in HW. Twenty-seven men and women (mean ± SD, age: 22 ± 2 years) participated in the 2-day investigation. Each subject completed 2 HW assessments 24 hours apart. Single-day comparisons of all trials for both days revealed no significant difference between the mechanical scale and the load cell (mean difference < 0.016 kg, p > 0.05). True underwater weight values were not significantly different between methods for either days (mean difference < 0.014 kg, p > 0.05) and accounted for a mean difference in percent fat (%FAT) of <0.108%. The 95% limits of agreement indicated a maximum difference between methods of 0.53% FAT. Both methods produced similar reliability SEM values (mechanical SEM < 0.72%FAT, load cell SEM < 0.75%FAT). In conclusion, there was no difference between mechanical scale and load cell measurements of underwater weights and the added precision of the load cell only marginally (<0.16%FAT) improved day-to-day reliability. Either a mechanical scale or load cell can be used for HW with similar accuracy and reliability in young adults with a body mass index of 18.7-34.4 (5-25%FAT).

Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching.

The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean ± SD age = 21 ± 2 years; body mass = 79 ± 15 kg; and height = 177 ± 7 cm) and 19 women (21 ± 3 years; 61 ± 9 kg; 165 ± 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means ± SD pre to post: 109.39° ± 10.16° to 116.63° ± 9.63°; p ≤ 0.05) but not for the men (111.79° ± 6.84° to 113.93° ± 8.15°; p > 0.05). There were no stretching-induced changes in MTS (women's pre to postchange in MTS: -0.35 ± 0.38; men's MTS: +0.17 ± 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 ± 0.41 vs. 0.97 ± 0.38; p ≤ 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p ≤ 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS.

Reproducibility and validity of bioimpedance spectroscopy for tracking changes in total body water: implications for repeated measurements.

Bioimpedance spectroscopy (BIS) has been used to track changes in total body water (TBW). Accurate TBW estimations can be influenced by both methodological and biological factors. One methodological variation that contributes to BIS TBW errors is the electrode placement. The purpose of the present study was to compare the reproducibility and validity of fixed-distance electrode placements (5 cm) with the standard single-site electrode placements. Twenty-nine subjects (fifteen men and fourteen women) participated in the reproducibility study, while sixty-nine subjects (thirty-three men and thirty-six women) participated in the validity study. The reproducibility study included two measurements that were taken 24 h apart, while the validity study consisted of a 12-week exercise intervention with measurements taken at weeks 1 and 12. TBW was estimated using BIS and 2H techniques. Reproducibility results indicated that fixed-distance electrodes reduced the day-to-day standard error of the measurement in men (from 1·13 to 0·81 litres) but not in women (0·47 litres). sem values were lower for women than for men, suggesting that BIS TBW estimates are sex dependent. Validity results produced similar accurate findings (mean difference < 0·21 litres). However, fixed-distance electrodes improved delta TBW errors (mean difference improvements>0·04 litres in men, women, and men and women combined). When tracking changes in TBW, fixed-distance electrodes may reduce reproducibility errors and allow for smaller changes to be detected. However, the reduction of reproducibility errors may be greater for men than for women. Therefore, reproducibility calculations should be based on the sex of the sample population.

Six weeks of high-intensity interval training with and without beta-alanine supplementation for improving cardiovascular fitness in women.

The purpose of the present study was to evaluate the effects of cycle ergometry high-intensity interval training (HIIT) with and without beta-alanine supplementation on maximal oxygen consumption rate (VO2 peak), cycle ergometer workload at the ventilatory threshold (VT W), and body composition. Forty-four women (mean +/- SD age = 21.8 +/- 3.7 years; height = 166.5 +/- 6.6 cm; body mass (BM) = 65.9 +/- 10.8 kg; VO2 peak = 31.5 +/- 6.2 ml x kg(-1) x min(-1)) were randomly assigned to 1 of 3 groups: beta-alanine (BA, n = 14) 1.5 g + 15 g dextrose powder; placebo (PL, n = 19) 16.5 g dextrose powder; or control (CON, n = 11). Testing was conducted at baseline (week 0), after 3 weeks (week 4), and after 6 weeks (week 8). VO2 peak (ml x kg(-1) x min(-1)) and VT W were measured with a metabolic cart during graded exercise tests on a corival cycle ergometer, and body composition (percent fat = % fat and fat-free mass = FFM) were determined by air displacement plethysmography. High-intensity interval training was performed on a corival cycle ergometer 3 times per week with 5 2-minute work intervals and 1-minute passive recovery with undulating intensities (90-110% of the workload recorded at VO2 peak) during each training session. VO2 peak increased (p 0.05) for the CON group. VT W increased (p

Viscoelastic creep in the human skeletal muscle-tendon unit.

The purposes of the present study were to (1) characterize viscoelastic creep in vivo in the human skeletal muscle-tendon unit and (2) to examine the consistency of these responses during a single 30-s stretch. Twelve volunteers (mean +/- SD = 22 +/- 3 years; height = 169 +/- 11 cm; mass = 70 +/- 17 kg) participated in two separate experimental trials. Each trial consisted of a 30-s constant-torque stretch of the plantar flexor muscles. Position (degrees) values were quantified at every 5-s period (0, 5, 10, 15, 20, 25, and 30 s) and the percent change in position was quantified for each 5-s epoch (0-5, 5-10, 10-15, 15-20, 20-25, and 25-30 s) relative to the total increase in the range of motion. In addition, the intraclass correlation coefficient (ICC) and standard errors of the measurement (SEM) were calculated for test-retest reliability. These results indicated that position increased over the entire 30-s stretch (P < 0.05), while the majority of the increases in position (73-85%) occurred during the first 15-20 s. ICC values were >or = 0.994 and SEM values (expressed as percentage of the mean) were

Validity of electromyographic fatigue threshold as a noninvasive method for tracking changes in ventilatory threshold in college-aged men.

The submaximal electromyographic fatigue threshold test (EMG(FT)) has been shown to be highly correlated to ventilatory threshold (VT) as determined from maximal graded exercise tests (GXTs). Recently, a prediction equation was developed using the EMG(FT) value to predict VT. The aim of this study, therefore, was to determine if this new equation could accurately track changes in VT after high-intensity interval training (HIIT). Eighteen recreationally trained men (mean +/- SD; age 22.4 +/- 3.2 years) performed a GXT to determine maximal oxygen consumption rate (V(O2)peak) and VT using breath-by-breath spirometry. Participants also completed a discontinuous incremental cycle ergometer test to determine their EMGFT value. A total of four 2-minute work bouts were completed to obtain 15-second averages of the electromyographic amplitude. The resulting slopes from each successive work bout were used to calculate EMG(FT). The EMG(FT) value from each participant was used to estimate VT from the recently developed equation. All participants trained 3 days a week for 6 weeks. Training consisted of 5 sets of 2-minute work bouts with 1 minute of rest in between. Repeated-measures analysis of variance indicated no significant difference between actual and predicted VT values after 3 weeks of training. However, there was a significant difference between the actual and predicted VT values after 6 weeks of training. These findings suggest that the EMG(FT) may be useful when tracking changes in VT after 3 weeks of HIIT in recreationally trained individuals. However, the use of EMG(FT) to predict VT does not seem to be valid for tracking changes after 6 weeks of HIIT. At this time, it is not recommended that EMG(FT) be used to predict and track changes in VT.

Acute effects of passive stretching on the electromechanical delay and evoked twitch properties.

The purpose of this study was to investigate the acute effects of passive stretching on the electromechanical delay (EMD), peak twitch force (PTF), rate of force development (RFD), and compound muscle action potential (M-wave) amplitude during evoked twitches of the plantar flexor muscles. 16 men (mean age +/- SD = 21.1 +/- 1.7 years; body mass = 75.9 +/- 11.4 kg; height = 176.5 +/- 8.6 cm) participated in this study. A single, square-wave, supramaximal transcutaneous electrical stimulus was delivered to the tibial nerve before and after passive stretching. The stretching protocol consisted of nine repetitions of passive assisted stretching designed to stretch the calf muscles. Each repetition was held for 135 s separated by 5-10 s of rest. Dependent-samples t tests (pre- vs. post-stretching) were used to analyze the EMD, PTF, RFD, and M-wave amplitude data. There were significant changes (P < or = 0.05) from pre- to post-stretching for EMD (mean +/- SE = 4.84 +/- 0.31 and 6.22 +/- 0.34 ms), PTF (17.2 +/- 1.3 and 15.6 +/- 1.5), and RFD (320.5 +/- 24.5 and 279.8 +/- 28.2), however, the M-wave amplitude did not change (P > 0.05). These findings suggested that passively stretching the calf muscles affected the mechanical aspects of force production from the onset of the electrically evoked twitch to the peak twitch force. These results may help to explain the mechanisms underlying the stretching-induced force deficit that have been reported as either "mechanical" or "electrical" in origin.