Cigarette smoking (CS) impact on cardiopulmonary function has been extensively investigated on sedentary, middle-aged smokers (SMK) with pulmonary disease, but not on young SMK with high fitness level. This study evaluated the cardiopulmonary and gas-exchange kinetics during and after moderate exercise in young, physically active SM without known diseases. Ten SMK (age: 21 ± 2 year., body mass: 78 ± 6 kg; stature: 1.79 ± 0.07 m; 12 ± 5 cigarette/day for 6 ± 2 year.; mean ± SD) and twelve non-smokers (CTRL; age: 24 ± 3 year., body mass: 78 ± 9 kg; stature: 1.80 ± 0.08 m) matched also for exercise habits performed an incremental cycloergometric test to assess maximum pulmonary oxygen uptake ( V̇_O_2 max ) and first ventilatory threshold (VT1). After pulmonary evaluation, participants performed four 6-min moderate-intensity tests at 90 V̇_E ), V̇_O_2 , heart rate (fH) and cardiac output ( Q̇ ). Despite similar static lung volumes, SMK exhibited lower peak expiratory flow (-21 V̇_O_2 max (3657 ± 325 vs. 3397 ± 316 ml∙min− 1 for CTRL and SMK, respectively; P = 0.009) and mechanical power at VT1 (201 ± 26 vs. 185 ± 16 W for CTRL and SMK respectively; P = 0.041). In on-phase, SMK demonstrated longer τ in Q̇ (+ 22 f_H (+ 56 V̇_O_2 (+ 41 V̇_E (+ 47 Q̇ (+ 51 f_H (+ 42 V̇_O_2 (+ 20 V̇_E (+ 42

High-frequency plyometric jump training (PT) may benefit tennis players, but little is known about how its weekly distribution affects performance and acute perceived soreness. The aim was to investigate the effects of PT, conducted at different weekly frequencies, on physical performance and muscle soreness in competitive tennis players. Eighteen competitive tennis players were randomly assigned to PT-1 (1 session/week) (n=9; age 17.0 +/- 2.0 yrs) or PT-3 (3 sessions/week) (n=9; age 19.0 +/- 3.9 yrs), both performing 180 jumps over 8 weeks. Countermovement vertical (CMVJ) and squat jumps (SJ), single-leg horizontal hop (SLHH), 10- and 20-m sprints, and a repeated change-of-direction (COD) test were measured pre- and post-intervention. Muscle soreness was recorded before and immediately after each PT session using a 7-point Likert scale. Both groups improved jump height, hop distance, sprint time, and repeated COD performance (p<0.05). No between-groups differences were noted for CMVJ (p=0.419), SJ (p=0.692), SLHH (p=0.512), 10- and 20-m sprints (p=0.658 and p=0.741), nor repeated COD performance (p=0.191). Distributing the same PT volume over three weekly sessions produces performance gains comparable to a single weekly session. However, the increase in muscle soreness was significantly lower in PT-3 than in PT-1 group. Higher-frequency, lower-dose PT may reduce acute muscle soreness perception while maintaining performance improvements.

The impact of cigarette smoking on the cardiorespiratory response to exhaustive exercise remains unclear. This study investigated the smoking effect on exercise tolerance by analyzing the cardiorespiratory and metabolic variables during an exhausting sinusoidal exercise in young physically active smokers (SM) without known cardiovascular and respiratory disease. Eight physically active male SM (22.1 ± 2.2 years; 79.9 ± 4.4 kg; maximum oxygen uptake, V ˙ O 2 max 3385 ± 341 mL·min-1) and 8 non-smokers (controls, 22.6 ± 1.4 years; 74.3 ± 7.9 kg; V ˙ O 2 max 3623 ± 302 mL·min-1) performed an exhausting sinusoidal cycling exercise. The work rate varied sinusoidally around a midpoint 50 W below the lactate threshold (LT), with an amplitude of ± 50 W and a 4-min cycle period. Midpoint, amplitude, and time-delay between mechanical and metabolic signals of pulmonary ventilation ( V ˙ E ), V ˙ O 2 , and heart rate (HR) were assessed sinusoid-by-sinusoid, as well as blood lactate ([La-]) and rate of perceived exertion (RPE). Despite similar LT (199 ± 26 vs. 219 ± 28 W for SM and controls, respectively), SM exhibited a lower time to exhaustion (2461 ± 386 vs. 4512 ± 1359 s for SM and controls, respectively; p = 0.001) than controls. No differences between groups emerged in midpoint, amplitude, and time delays, as well as in [La-] and RPE. In SM, V ˙ O 2 midpoint remained constant, whereas in controls during the last cycle was higher compared to the first one (p = 0.001). In both groups, HR (p < 0.01) and V ˙ E midpoint increased from the first to the last cycle (p < 0.05). The cigarette smoking-induced exercise intolerance suggests metabolic and ventilatory impairments during sinusoidal cycle exercise even in young, physically active SM with no cardiovascular and respiratory disease.

This study aimed to compare the acute physiological and mechanical responses elicited by two commonly used high-intensity training modalities, speed endurance training (SET) and repeated-sprint exercise (RSE), in moderately trained soccer players. Fourteen male soccer players (age 21 ± 2 years, height 181 ± 5.5 cm, body mass 74 ± 8.3 kg) were randomly assigned to either speed endurance training (SET; 6 × 15-s all-out shuttle runs with 90 s passive recovery) or repeated-sprint exercise (RSE; 3 × 6 × 5-s all-out linear and shuttle runs with 20 s recovery between repetitions and 3 min between series). External load was assessed using GPS technology, while heart rate (HR), blood lactate concentration (La−), and session rating of perceived exertion (s-RPE) were used to quantify internal load. GPS-derived mechanical variables included distance covered at different speed thresholds, number of accelerations and decelerations, maximal speed, and estimated metabolic power. Physiological measures also included mean and peak HR, time spent in five HR intensity zones, and post-exercise blood lactate concentrations. RSE induced a higher neuromuscular load, reflected by more accelerations and decelerations > 3 m s−2 and greater distances covered at metabolic power zones 10–25 W kg−1. SET elicited higher blood lactate responses, indicating greater anaerobic contribution. Both protocols produced comparable top speeds and sprint decrement, and similar HRpeak and time spent at 80–90

The evolution of indoor skydiving from military origins to a globally recreational pursuit has attracted individuals without prior specific training, exposing them to the heightened risk of muscle–joint injuries associated with indoor skydiving. This study aims to assess the muscular excitation patterns in highly skilled instructors to determine the optimal activation strategies for preventing musculoskeletal injuries. Nine expert indoor skydiving instructors (M/F: 8/1; age 31 ± 7 years; body mass: 70.5 ± 11.1 kg; stature: 1.74 ± 0.09 m) were enrolled. The surface electromyographic signal was recorded on the anterior deltoid, AD; posterior deltoid, PD; pectoralis major, PM; latissimus dorsi, LD; rectus abdominis, Rabd; erector spinae, ES; rectus femoris, RF; and biceps femoris, BF for each position: PRONE, SUPINE, SIT, and head-down (HD). A synchronous heart rate was recorded to assess the cardiac engagement. The neuromuscular load (NeLo), representative of the excitation amplitude of a muscle set, was determined for each position across different body regions. PRONE and SUPINE were the least demanding in terms of cardiac engagement (67 ± 6 and 85 ± 8 bpm, respectively) and exhibited the lowest neuromuscular excitation (24 ± 10 and 24 ± 8% Max, respectively). By contrast, HD exhibited the highest cardiac (127 + 18 bpm) and neuromuscular (71 + 11% Max) engagement and particularly in the lower-trunk and lower-limbs muscles. SIT predominantly engaged upper-trunk and shoulder muscles. The findings indicate the significant engagement of the musculature surrounding the shoulder joint and that responsible for lower-trunk stabilization in maintaining the investigated positions. A targeted training regimen on strengthening these muscles is advised before practicing indoor skydiving to prevent shoulder joint injuries or lower back muscle overloads.

Muscle stretching comprises various modalities that differ in methodological aspects and provide distinct acute and long-term effects on maximal range of motion (ROMmax) and muscle strength. This narrative review aims to: i) describe each stretching modality in detail, including current approaches to quantifying intensity and volume; ii) examine how variations in these parameters influence acute and chronic adaptations in ROMmax and strength; and iii) provide practical guidance by highlighting each method’s advantages, limitations, and effectiveness in achieving flexibility improvements with minimal impact on strength. The reviewed modalities include passive or active static stretching, dynamic or ballistic stretching, and proprioceptive neuromuscular facilitation (PNF). Intensity is commonly measured as stretch-induced discomfort (static), movement velocity or frequency (dynamic/ballistic), or contraction effort (PNF). Volume is quantified as total time at a given

BACKGROUND:Stretching has wide appeal, but there seems to exist some mismatch between its purported applications and what the evidence shows. There is compelling evidence for some stretching applications, but for others, the evidence seems heterogeneous or unsupportive. The discrepancies even affect some systematic reviews, possibly due to heterogeneous eligibility criteria and search strategies. This consensus paper seeks to unify the divergent findings on stretching and its implications for both athletic performance and clinical practices by delivering evidence-based recommendations. METHODS:A panel of 20 experts with a blend of practical experience and scholarly knowledge was assembled. The panel meticulously reviewed existing systematic reviews, defined key terminologies (e.g., consensus definitions for different stretching modes), and crafted guidelines using a Delphi consensus approach (minimum required agreement: 80%). The analysis focused on 8 topics, including stretching's acute and chronic (long-term) effects on range of motion, strength performance, muscle hypertrophy, stiffness, injury prevention, muscle recovery, posture correction, and cardiovascular health. RESULTS:There was consensus that chronic and acute stretching (a) improves range of motion (although alternatives exist) and (b) reduces muscle stiffness (which may not always be desirable); the panel also agreed that chronic stretching (c) may promote vascular health, but more research is warranted. In contrast, consensus was found that stretch training does not (a) contribute substantively to muscle growth, (b) serve as an all-encompassing injury prevention strategy, (c) improve posture, or (d) acutely enhance post-exercise recovery. CONCLUSION:These recommendations provide guidance for athletes and practitioners, highlighting research gaps that should be addressed to more comprehensively understand the full scope of stretching effects.

The current study compared the spatial excitation of the prime movers when performing the overhead press with the barbell passing in front (front-OHP) or behind the neck (back-OHP) using high-density surface electromyography (HD-sEMG). Fourteen resistance trained men performed both exercises within a non-fatiguing set with 8-RM as the external load. The HD-sEMG amplitude and the muscle excitation centroid of anterior deltoid, lateral deltoid, posterior deltoid, upper trapezius, pectoralis major and triceps brachii muscles were recorded during the ascending and the descending phase. During the ascending phase, the front-OHP showed a superior HD-sEMG amplitude of the anterior deltoid (ES = 1.03) and the pectoralis major (ES = 0.70). During the descending phase, the front-OHP showed a superior HD-sEMG amplitude of the anterior deltoid (ES = 1.00) and the pectoral major (ES = 0.74), while the back-OHP showed superior excitation of the posterior deltoid (ES = 1.11), the upper trapezius (ES = 0.72) and triceps brachii (ES = 2.01). During the ascending phase, the front-OHP showed a more medial centroid of the lateral deltoid (ES = 2.30). During the descending phase, the front-OHP showed a more lateral centroid of the lateral deltoid (ES = 0.87), whereas the centroid of the posterior deltoid (ES = 0.63) and the triceps brachii (ES = 0.68) was more medial. Additionally, the centroid was more cranial in the front- vs. the back-OHP for the posterior deltoid (ES = 1.10), while for the pectoralis major the centroid was more caudal (ES = 0.62). The front- and back-OHP appeared to provide different overall excitation in the prime movers. Moreover, distinct spatial excitation patterns were observed, making both exercises suitable for the training routine.

This study investigated the intra-day and inter-day reliability of electrical impedance myography (EIM) components and explored sex and regional differences in healthy adults' anterior thigh muscles. Using a multifrequency device, impedance values across various frequencies, alongside 50-kHz resistance (R), reactance (Xc), and phase angle (PhA) were assessed in both sexes and at whole anterior thigh, proximal and distal regions. Findings revealed excellent reliability (ICC > 0.90) and low standard error of measurement (<5.0 %) for impedance at all frequencies, 50-kHz R, Xc, and PhA regardless of sex or measurement region during both intraday and inter-day assessments. Moreover, differences were observed between women and men across most parameters, except for Xc, indicating the sensitivity of EIM in detecting established disparities in tissue composition between sexes. Notably, whole anterior thigh impedance at all frequencies and 50-kHz R, Xc, and PhA displayed dissimilarities compared to proximal or distal regions in both sexes. Additionally, women exhibited differences between proximal and distal regions in the 100-kHz impedance and 50-kHz impedance, R, Xc, and PhA highlighting possible variations in tissue composition along the muscle length compared to men. These findings underscore the relevance of electrode placement and emphasize sex-specific differences in EIM assessments within anterior thigh muscle regions.

Objectives: The present study compared the amplitude and spatial distribution of muscle excitation between a seated row performed with a fixed scapular position (fixed-SR) and a free scapular position (free-SR) in resistance-trained men, analyzing concentric and eccentric phases separately using high-density surface EMG (HD-sEMG). Methods: Fourteen resistance-trained males (age: 25 ± 4 years; stature: 1.74 ± 0.06 m; body mass: 76.22 ± 5.73 kg) performed fixed-SR and free-SR in a randomized cross-over design using 8-repetition maximum as the load for both variations. HD-sEMG grids recorded the activity from the upper/middle/lower trapezius, latissimus dorsi, lateral/posterior deltoid, biceps brachii, triceps brachii, and erector spinae. Normalized root mean squared (RMS) amplitude and excitation centroids in the mediolateral and craniocaudal planes were computed for the concentric and eccentric phases. Data were analyzed using repeated-measures statistical models, with significance set at p < 0.05. Results: During the concentric phase, nRMS amplitude was greater for the posterior deltoid in fixed-SR compared with free-SR (effect size [ES] = 0.66), whereas no between-condition difference was observed for the remaining muscles. During the eccentric phase, nRMS amplitude was greater in the fixed-SR for the middle trapezius (ES = 0.67) and the latissimus dorsi (ES = 0.85), with no between-condition differences detected for the remaining muscles. The centroid position analysis revealed that, during the eccentric phase, the middle trapezius centroid was located more laterally in the fixed-SR condition (ES = 0.54), while the posterior deltoid centroid was positioned more caudally in the fixed-SR compared with the free-SR condition (ES = 0.22). Conclusions: The fixed-SR and free-SR conditions produce comparable overall muscle excitation patterns, while showing some quantitative and spatial differences in selected upper-back muscles. These results suggest that scapular constraint influences the distribution of muscular excitation rather than overall excitation levels. Accordingly, both variations can be effectively used in resistance training, selecting to fix or free the scapulae depending on the emphasis on the scapular movements rather than a substantial difference in muscle excitation.

Cigarette smoking (CS) is the major preventable cause of mortality, leading to systemic modifications that impair the cardiorespiratory and metabolic response to exercise. Although extensive evidence exists regarding the effects of CS in sedentary, middle-aged smokers (SM) with pulmonary disease, data concerning young, physically active SM remain limited and controversial. Therefore, this study sought to evaluate the cardiorespiratory and metabolic kinetics during moderate exercise in young, physically active SM without known lung or cardiovascular disease. We hypothesized that, despite their age, brief smoking history and good fitness level, which could have counterbalanced the harmful CS effects, SM would exhibit elongated kinetics. This would be a result of early developed alterations in oxidative stress, inflammatory state, autonomic response and O 2 delivery. This study involved 10 SM (age: 21±2 yr., body mass: 78±6 kg; stature: 1.79±0.07 m; 12±5 cigarette/day for 6±2 yr.; mean±SD) and 12 non-smokers (CTRL; age: 24±3 yr., body mass: 78±9 kg; stature: 1.80±0.08 m) matched for age and exercise habits. Participants completed an incremental test on a cycle ergometer to determine the maximum pulmonary oxygen uptake (V'O2max). After pulmonary evaluation, participants performed four 6-min moderate-intensity tests at 90% of the first ventilatory threshold (VT1). Mono-exponential function was applied to assess the time constant (τ) of expiratory ventilation (V'E), V'O2, heart rate ( f H) and cardiac output (Q) during the increasing (on-phase) and decreasing (off-phase) transients. SM had similar static lung volumes compared to CTRL but had lower peak expiratory flow (-21%; P=0.004) and maximal voluntary ventilation (-12%; P=0.004). Moreover, SM exhibited lower V'O2max (3657±325 vs 3397±316 ml·min-1 for CTRL and SM, respectively; P=0.037) and mechanical power at VT1 (201±26 vs 185±16 W for CTRL and SM respectively; P=0.045). During the on-phase, τ in SM was longer for f H (+24%; P=0.006), V'O2 (+40%; P=0.009), V'E (+49%; P=0.018) and Q (+22%; P=0.024). Similarly, during the off-phase SM showed longer τ for f H (+37%; P=0.014), V'O2 (+20%; P=0.004), V'E (+35%; P=0.045) and Q (+51%; P=0.020). These findings demonstrate that CS affects cardiorespiratory and metabolic kinetics at moderate exercise even in young individuals with relatively short smoking history. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

We assessed passive static stretching (PS) effects on the spatial distribution of muscle excitation (SDME) of the stretched (SL) and contralateral non-stretched limb (CL) during maximum voluntary isometric contractions (MVC). Before (PRE) and after 5-min PS, immediately (POST), at min 5 (POST5) and 10 (POST10), range of motion (ROM), maximal M-wave (Mmax) and MVC of both limbs were assessed in thirty men. During MVC, high-density surface electromyographic signals from the gastrocnemius medialis (GM) and lateralis (GL) were collected. The root mean square (RMS) and centroid coordinates were then obtained. During PS, discomfort perception (VAS), proximal and distal GM architecture were recorded. At POST, ROM increased and MVC decreased together with RMS in both limbs (P < 0.05). A cranio-caudal shift in SDME occurred in both muscles of SL and CL (P < 0.01) that persisted only in SL until POST5 in GM (P = 0.04), and POST10 in GL (P = 0.01). During PS, VAS was high (>8.0), and fascicle length and angle increased from rest (P < 0.01). No differences between GM portions were found in muscle architecture and in Mmax (P > 0.05). The results suggest involvement of central neural mechanisms in SDME shift. The prolonged effect in SL compared to CL indicates a possible additional contribution from mechanical mechanisms.

The present study investigated muscle damage and the repeated-bout effect after a typical Nordic hamstring exercise session. Thirteen trained male adults were recruited. Muscle damage was monitored through eccentric strength, passive range of motion, muscle soreness, and muscle swelling. Assessments were performed at baseline and 1 (day 1), 2 (day 2), 3 (day 3), and 4 (day 4) days after 24 Nordic hamstring exercise repetitions. The procedures were replicated after 4 weeks to examine the repeated-bout effect. After the first bout, the hamstring eccentric strength decreased up to day 3 (effect size range:-2.28/-1.95). The passive range of motion decreased up to day 4 (effect size range:-1.62/-0.64), while the muscle soreness increased on day 2 (effect size=1.63) and day 3 (effect size=1.53). No change in muscle swelling was observed. After the second bout, the hamstring eccentric strength (effect size=- 1.20) decreased only on day 1. The passive range of motion decreased up to day 3 (effect size=- 0.85/-0.34). These changes were by a smaller magnitude compared to the first bout. The first Nordic hamstring exercise bout impaired hamstring strength and passive range of motion, with muscle soreness also perceived, while the second bout reduced muscle damage symptoms and shortened the time to recovery. While recovery is needed when a Nordic hamstring exercise session is performed for the first time, following Nordic hamstring exercise sessions may scarcely interfere with the training routine.

The current study compared the spatial excitation of the primary muscles during the lat pull-down exercise with the bar passing in front (front-LPD) or behind the neck (back-LPD) using high-density electromyography. Fourteen resistance trained men performed a front-LPD or a back-LPD within a non-fatiguing set with 8-RM as the external load. The muscle excitation centroid of latissimus dorsi, middle trapezius, pectoralis major, biceps brachii, triceps brachii and posterior deltoid muscles were recorded during the ascending and the descending phase. During the descending phase, the front-LPD showed superior excitation of the latissimus dorsi (ES = 0.97) and the pectoralis major (ES = 1.17), while in the ascending phase, the back-LPD exhibited superior excitation of the latissimus dorsi (ES = 0.63), and the front-LPD showed superior excitation of the biceps brachii (ES = 0.41) and the posterior deltoid (ES = 1.77). During the descending phase, the front-LPD showed a more lateral centroid of the latissimus dorsi (ES = 0.60), the biceps brachii (ES = 0.63) and the triceps brachii (ES = 0.98), while the centroid was more medial for the middle trapezius (ES = 0.58). The centroid of the middle trapezius was also more medial in the front-LPD during the ascending phase (ES = 0.85). The pectoralis major centroid was more cranial in the front-LPD for both the descending (ES = 1.58) and the ascending phase (ES = 0.88). The front-LPD appears to provide overall greater excitation in the prime movers. However, distinct spatial excitation patterns were observed, making exercise suitable for the training routine.

ABSTRACT:Trecroci, A, Cavaggioni, L, Rossi, A, Bongiovanni, T, Invernizzi, PL, Formenti, D, and Longo, S. Self-regulated learning assessment in young soccer players: beyond competitive levels. J Strength Cond Res 39(1): e56-e61, 2025-This study explores self-regulated learning (SRL) among young soccer players, transcending the traditional focus on competitive levels. One hundred twenty-four soccer players of regional and provincial levels from under 14 to under 17 age groups voluntarily participated in the study and were combined into a single group. A median-split method based on total time performance was used to separate players into low performers (LPs) and high performers (HPs) from a 90° change of direction dribbling test. The self-regulation of learning-self-report scale for sport practice (SRL-SRS-SP) with a 5-factor solution (planning, reflection, effort, self-efficacy, and self-supervision) and 31 items was used. The score was based on a 1-5 Likert scale. The level of significance was set at p -value < 0.05. The SRL-SRS-SP total score by HP players differed significantly from that of LP players ( p = 0.015). Regarding each subscale, HP players showed significantly higher scores than LP players ( p = 0.011) for planning, whereas no differences were observed for the remaining factors ( p ≥ 0.05). The main observation of this study revealed that HP soccer players had a greater level of engagement in the learning process with a remarkable ability to plan for specific improvement than LP peers. This suggests that the competitive level might not be the sole determinant of differences in SRL. Therefore, strength and conditioning coaches should emphasize metacognitive and motivational components because of their crucial role in enhancing technical and physical performance.

PURPOSE:Cigarette smoking (CS) induces systemic changes that impair cardiorespiratory and muscular function both at rest and during exercise. Although these abnormalities are reported in sedentary, middle-aged smokers (SM) with pulmonary disease, few and controversial studies focused on young, physically active SM at the early stage of smoking history. This study aimed at assessing the effect of CS on cardiorespiratory and metabolic response during an incremental test and the subsequent recovery in young, physically active SM without known lung or cardiovascular disease. METHODS:After pulmonary function evaluation, 12 SM (age: 22±2 yr; body mass: 75±8 kg; stature: 1.78±0.06 m; 12±4 cigarette per day for 6±2 yr; mean ± SD) and 12 non-SM (control group; age: 23±1 yr; body mass: 76±8 kg; stature: 1.79±0.08 m) matched for age and exercise habits underwent an exhaustive incremental step test (25 W/2 min) on a cycle ergometer. Pulmonary O 2 uptake (V̇O 2 ), expiratory ventilation (V̇ E ), heart rate ( fH ) responses and lactate concentration were assessed during the test and subsequent recovery. RESULTS:Despite similar static lung volumes, SM reported lower peak expiratory flow (-23%; P = 0.003) and maximal voluntary ventilation (-10%; P = 0.003). At submaximal exercise, no differences in the cardiorespiratory and metabolic were noted between the two groups. However, SM exhibited ventilatory ( P < 0.01) and lactate thresholds at lower work rates ( P = 0.01). At peak exercise, SM exhibited lower V̇O 2 (-8%; P = 0.02), mechanical power (-11%; P = 0.02), and V̇ E (-9%; P = 0.01). During recovery, SM showed longer time constants (τ) in V̇O 2 (+52%; P = 0.002), V̇ E (+19%; P = 0.027) and fH (+21%; P = 0.022) and smaller fH at 30 s of recovery (HRR30; -31%; P = 0.032). CONCLUSIONS:These results are compatible with an early CS-related impairment of the cardiorespiratory and metabolic function even in young individuals with relatively short smoking history.

This study investigated the synergistic difference in the effect of stretching on electromechanical delay (EMD) and its components, using a simultaneous recording of electromyographic, mechanomyographic, and force signals. Twenty-six healthy men underwent plantar flexors passive stretching. Before and after stretching, the electrochemical and mechanical components of the EMD and the relaxation EMD (R-EMD) were calculated in gastrocnemius medialis (GM), lateralis (GL) and soleus (SOL) during a supramaximal motor point stimulation. Additionally, joint passive stiffness was assessed. At baseline, the mechanical components of EMD and R-EMD were longer in GM and GL than SOL (Cohen’s d from 1.78 to 3.67). Stretching decreased joint passive stiffness [-22(8)%, d = -1.96] while overall lengthened the electrochemical and mechanical EMD. The mechanical R-EMD components were affected more in GM [21(2)%] and GL [22(2)%] than SOL [12(1)%], with d ranging from 0.63 to 1.81. Negative correlations between joint passive stiffness with EMD and R-EMD mechanical components were found before and after stretching in all muscles (r from -0.477 to -0.926; P from 0.007 to <0.001). These results suggest that stretching plantar flexors affected GM and GL more than SOL. Future research should calculate EMD and R-EMD to further investigate the mechanical adaptations induced by passive stretching in synergistic muscles.

The current study compared the muscle excitation of the primary and stabilizer muscles during standing overhead press performed with either the barbell (barbell-OHP) or the kettlebells (kettlebell-OHP), using surface electromyography. Ten male StrongFirst-certified instructors in the OHP, performed either the barbell-OHP or the kettlebell-OHP in a non-fatiguing set with an external load of 8-RM. Muscle excitation of the anterior deltoid, lateral deltoid, posterior deltoid, upper trapezius, triceps brachii, flexor carpi ulnaris, latissimus dorsi, rectus abdominis, external oblique, erector spinae and gluteus maximus was recorded during both the descending and the ascending phase. During the ascending phase, the kettlebell-OHP showed superior excitation of the flexor carpi ulnaris (p < 0.01, ES = 1.90), erector spinae (p = 0.04, ES = 0.71) and gluteus maximus (p < 0.01, ES = 1.00) while in the descending phase, the kettlebell-OHP exhibited superior excitation of the anterior deltoid (p = 0.04, ES = 0.69), upper trapezius (p = 0.04, ES = 0.69), flexor carpi ulnaris (p < 0.01, ES = 4.04) and erector spinae (p = 0.04, ES = 0.70). No between-exercise difference was observed for the lateral deltoid, posterior deltoid, triceps brachii, latissimus dorsi, rectus abdominis and external oblique. The kettlebell-OHP may be more effective than the barbell-OHP in recruiting both primary movers and stabilizers, making it a potentially valuable addition to training for increased strength and rehabilitation benefits. However, the different barbell peculiarities make both resistances suitable for inclusion in a training routine.