Background:Long-distance running performance is influenced by multiple physiological factors, among which aerobic capacity has traditionally been considered particularly important. Although recent evidence suggests that sprint-related characteristics also play an important role, the determinants of long-distance running performance in female athletes remain insufficiently understood. Purpose:This exploratory cross-sectional study aimed to examine the relationships between long-distance running performance and multiple physiological determinants, performance-related indices, performance-related characteristics, and physiological parameters, including aerobic capacity, running economy (RE), onset of blood lactate accumulation (OBLA), 100-m sprint time, and maximal rate of lactate accumulation (vLamax), in female long-distance runners. Methods:Thirteen trained female runners participated in this study. Physiological variables, including peak oxygen uptake (V̇O2peak) as an index of aerobic capacity, were assessed using treadmill-based step- and ramp-incremental tests, during which RE was defined as oxygen uptake at a running speed of 180 m·min⁻1. Sprint performance was evaluated using a 100-m maximal sprint test on an outdoor all-weather track. Results:Long-distance running performance was defined as the seasonal best time in the 3,000-m event (3,000-m SB: 10:07.8 ± 0:21.1). The 3,000-m SB was significantly correlated with 100-m sprint time (r = 0.731, p = 0.003), RE (r = 0.662, p = 0.010), vLamax (r = -0.657, p = 0.011), and running velocity at OBLA (r = -0.612, p = 0.020). No significant correlation was observed between 3,000-m SB and V̇O2peak. All significant correlations remained statistically significant after Benjamini-Hochberg false discovery rate correction. Conclusion:These findings suggest that sprint-related characteristics, RE, and lactate-related performance indices are associated with long-distance running performance in female long-distance runners.

OBJECTIVE:To investigate whether shear wave elastography (SWE)-derived elasticity and viscosity indices of the medial gastrocnemius are associated with the velocity-dependent characteristics of passive ankle joint torque during muscle elongation at different angular velocities. METHODS:SWE measured the shear wave velocity, elastic modulus, viscosity coefficient, and shear wave dispersion at multiple static joint positions (at plantarflexion angles of 30°, 15°, and 0°) in 15 healthy young men. Passive dorsiflexion from 30° plantarflexion to 20° dorsiflexion was applied at multiple angular velocities using a dynamometer. The structural damping coefficient in a lumped-parameter model of the ankle and associated muscles was defined as the slope of the regression relating peak torque to angular velocity. RESULTS:No correlation was observed between the SWE-derived viscosity coefficient and the SWE-derived dispersion slope, indices of viscous properties (r = -0.013, p = 0.930). The shear wave velocity, elastic modulus, and viscosity coefficient increased with dorsiflexion, but their change patterns differed. The shear wave dispersion was unaffected by the ankle angle. Significant correlations with the structural damping coefficient were observed only for the viscosity coefficient at 15° (r = 0.652, p = 0.008) and 0° (r = 0.537, p = 0.039) plantarflexion. CONCLUSIONS:The SWE-derived viscosity coefficient, unlike the shear wave dispersion slope, demonstrated a moderate correlation with structural damping in this small study cohort when SWE was measured during moderate stretch of the muscle (plantarflexion). These preliminary findings suggest that the SWE-derived viscosity coefficient may serve as a superior quantitative index for evaluating intrinsic muscle viscosity.

Introduction:Badminton-specific agility, characterized by frequent lunges performed with the leg on the racket-holding side, is a key determinant of overall badminton performance. Although leg extension strength is expected to play a significant role, the factors that influencing badminton-specific agility remain unclear. This study therefore aimed to test the hypothesis that knee extension strength is correlated with badminton-specific agility in world-class and elite/international-level badminton players. Methods:This study included twenty-seven male and twenty-three female professional badminton players from the Japanese national team. Participants completed two tests: (1) a badminton-specific agility test measuring the time required to reach sensors at the four corners of a singles court using badminton-specific movement, and (2) an isokinetic knee extension strength test at angular velocities of 60 °/s and 180 °/s. The Spearman rank-order correlation coefficients were used to assess the relationships between them (P < .05). Results and discussion:Significant inverse correlations were found between knee extension torque normalized to body mass for the leg opposite the racket-holding hand and badminton-specific agility at both 60 °/s and 180 °/s (males at 60 °/s: rs  = -.619; 180 °/s: rs  = -.579; females at 60 °/s: rs  = -.445; 180 °/s: rs  = -.446). In contrast, only the same-side leg at 60 °/s showed a significant inverse correlation (males: rs  = -.413; females: rs  = -.490). Overall, these results show that knee extension strength is crucial for badminton-specific agility among world-class and elite/international-level male and female badminton players. Furthermore, our findings suggest differing demands for force production between the legs on the same and opposite sides of the racket-holding hand.

This study aimed to investigate the relationship between medial gastrocnemius (MG) shear modulus and viscosity, as measured using shear wave elastography (SWE), and the capacity for rapid force production, specifically the rate of torque development (RTD). Twenty-nine healthy young men participated in this study. The passive shear modulus and viscosity (viscosity coefficient) of the MG were measured using SWE. Viscosity was quantified at 15° of plantarflexion, whereas shear modulus was measured at 0° and 15° of plantarflexion. Participants performed maximal isometric plantarflexion at 0°. RTD was calculated over 0–50 (RTD50) and 0–100 ms (RTD100) and was normalized to peak torque. The relationships between MG viscosity, MG shear modulus, RTD, and peak torque were analysed using Pearson product-moment correlation coefficients. Viscosity at 15° of plantarflexion was significantly positively correlated with RTD50 (r = 0.507, p = 0.005) and RTD100 (r = 0.399, p = 0.032). Shear modulus at 0° of plantarflexion was also significantly correlated with RTD50 (r = 0.479, p = 0.009) and RTD100 (r = 0.377, p = 0.044). No significant correlations were found between peak torque and any viscoelastic parameters. Shear modulus at 15° of plantarflexion did not correlate with RTD. This study provides initial evidence that skeletal muscle viscosity may be crucial in determining rapid force production. In addition to acting as a property characterized by velocity-dependent resistance, muscle viscosity may contribute to stable and efficient force transmission during the initial phase of contraction.

The quadriceps femoris is larger in inferior distance runners than in superior distance runners within a cohort of competitive athletes (i.e., highly trained/elite runners). We hypothesize that distance runners who are less efficient at utilizing elastic energy during running show excessive hypertrophy of the quadriceps femoris. This study aimed to examine the relationship between thigh muscle size and indices of elastic energy utilization during running in highly trained/elite distance runners. Fifteen male distance runners (personal best time for 5000-m, 13'45″11 ± 19″91) participated. The volumes of the quadriceps femoris, hamstrings, and adductors were measured using magnetic resonance imaging and normalized to the participant's body mass. The participants performed 60-m distance race-paced running and sprinting on an all-weather indoor track. Ground reaction force data were recorded and used to calculate vertical stiffness (kvert) and leg stiffness (kleg) as indices of elastic energy utilization. The kvert and kleg during distance race-paced running and sprinting were negatively correlated with the relative volume of the quadriceps femoris (r = -0.692--0.522, rs = -0.797, p < 0.05) but not with the hamstrings and adductors (r = -0.189-0.030, rs = -0.015-0.015, p > 0.05). In conclusion, highly trained/elite distance runners who are less efficient at utilizing elastic energy may accumulate more mechanical load on the quadriceps femoris during their daily running, which may be associated with a larger quadriceps femoris.

Tanji, F, Ohnuma, H, Ando, R, Yamanaka, R, Ikeda, T, and Suzuki, Y. Longer ground contact time is related to a superior running economy in highly trained distance runners. J Strength Cond Res 38(5): 985-990, 2024-Running economy is a key component of distance running performance and is associated with gait parameters. However, there is no consensus of the link between the running economy (RE), ground contact time, and footstrike patterns. Thus, this study aimed to clarify the relationship between RE, ground contact time, and thigh muscle cross-sectional area (CSA) in highly trained distance runners and to compare these parameters between 2 habitual footstrike patterns (midfoot vs. rearfoot). Seventeen male distance runners ran on a treadmill to measure RE and gait parameters. We collected the CSAs of the right thigh muscle using a magnetic resonance imaging scanner. The RE had a significant negative relationship with distance running performance (r = -0.50) and ground contact time (r = -0.51). The ground contact time had a significant negative relationship with the normalized CSAs of the vastus lateralis muscle (r = -0.60) and hamstrings (r = -0.54). No significant differences were found in RE, ground contact time, or normalized CSAs of muscles between midfoot (n = 10) and rearfoot (n = 7) strikers. These results suggest that large CSAs of knee extensor muscles results in short ground contact time and worse RE. The effects of the footstrike pattern on the RE appear insignificant, and the preferred footstrike pattern can be recommended for running in highly trained runners.

The purpose of this study was to statistically compare the rate of torque development normalized by maximal strength (relative RTD) across ankle angles. Additionally, this study was aimed at exploring the correlation coefficients between relative RTD and passive stiffness of the medial gastrocnemius (MG) at different ankle angles. Twenty-two healthy men and women (age: 31 ± 4 years) performed randomly-ordered explosive isometric plantar flexions at plantarflexed (15°), neutral (0°), and dorsiflexed (− 15°) angles; relative RTD comprised the slope of the time–torque curve normalized to maximal torque. The shear wave velocity (SWV; index of stiffness) of the MG at rest was measured at each angle using ultrasound shear wave elastography. The relative RTD was greater at 15° than − 15° for 0–50, 0–100, and 0–150 ms time-windows and at 15° than 0° for the 0–150 ms time-window (P < 0.05), although peak torque was lower at 15° than 0° and − 15° (P < 0.05). The relative RTD for the 0–50 ms time-window correlated with SWV at − 15° (rs = 0.475, P < 0.05), but not at 15º and 0º. Furthermore, the correlation coefficient of RTD for the 0–100 ms time-window with SWV was significantly greater at − 15° (rs = 0.420) than 0 ° (rs = − 0.109). A greater relative RTD occurs at plantarflexed angles (i.e., the ascending limb of the force–length curve) in the triceps surae, and relative RTD is strongly related to passive MG stiffness at dorsiflexed angles (i.e., longer muscle lengths).

AbstractWe developed a test to evaluate badminton‐specific endurance. The study included 10 female badminton players. Five participants were ranked in Japan's top 100 national rankings (ranked), whereas the others were unranked (unranked). Participants reacted quickly with badminton‐specific steps from the base center to the four sensors at each corner of a singles badminton court. On each set, they reacted eight times to randomized instructions at stage‐specific intervals (1.2, 1.0, and 0.8 s for stages 1, 2, and 3, respectively), which were performed six times with a rest of 20 s in each stage (8 movements × 6 sets × 3 stages). On a different day, participants ran on a treadmill as a comparative test. Blood lactate concentration (BLa) was measured on each test. In the badminton‐specific test, ranked participants had lower BLa (4.2 ± 1.7 mM vs. 6.3 ± 3.1 mM), with medium or large effect sizes. The average reach time to sensors was shorter in ranked participants (1.56 ± 0.03 s vs. 1.62 ± 0.07 s), with medium or large effect sizes. BLa was similar between groups, with trivial or small effect sizes in the running test. These results suggest that the newly developed test can evaluate badminton‐specific endurance.

PURPOSE:Long-distance running performance has been reported to be associated with sprint performance in highly trained distance runners. Therefore, we hypothesized that sprint training could enhance distance running and sprint performance in long-distance runners. This study examined the effect of 6-week sprint training on long-distance running and sprint performance in highly trained distance runners. METHODS:Nineteen college runners were divided into control (n = 8) and training (n = 11) groups. Participants in the training group performed 12 sprint training sessions in 6 weeks, while those in the control group performed 12 distance training sessions. Before and after the interventions, maximal oxygen uptake (V˙O2max), O2 cost during submaximal running (290 m·min-1 and 310 m·min-1 of running velocity), and time to exhaustion (starting at 290 m·min-1 and increased 10 m·min-1 every minute) were assessed on a treadmill. Additionally, the 100-m and 400-m sprinting times and 3000-m running time were determined on an all-weather track. RESULTS:In the control group, no measurements significantly changed after the intervention. In the training group, the time to exhaustion, 100-m and 400-m sprinting times, and 3000-m running time improved significantly, while V˙O2max and O2 cost did not change. CONCLUSIONS:These results showed that 6-week sprint training improved both sprint and long-distance running performance in highly trained distance runners without a change in aerobic capacity. Improvement in the time to exhaustion without a change in V˙O2max suggests that the enhancement of long-distance running performance could be attributable to improved anaerobic capacity.

We investigated the relationship between intramuscular adipose tissue (IntraMAT) and muscle stiffness (passive and mechanical) and lengthening in young individuals, hypothesizing that (1) passive muscle stiffness is negatively correlated with the IntraMAT content, and (2) the IntraMAT content is negatively correlated with mechanical changes in muscle stiffness and fascicle length during passive dorsiflexion. Twenty men and women (20.3 ± 1.3 years) participated in this study. Axial T1-weighted magnetic resonance imaging was performed at the thickest point of the medial gastrocnemius (MG) to measure the IntraMAT cross-sectional area (CSA) and muscle tissue CSA (units; cm2). The shear wave velocity (SWV) and fascicle length at the three ankle joint angles, namely 15° with plantarflexion (PF15), 0° with neutral position (NP), and 15° with dorsiflexion (DF15), were measured as parameters of muscle stiffness (unit; m/s) and lengthening (unit; cm) using ultrasound shear wave elastography and B-mode imaging. We further calculated the changes in SWV and fascicle length from PF15 to NP and from NP to DF15 as mechanical muscle stiffness and lengthening, respectively. There was a relationship between IntraMAT CSA and absolute SWV at DF15 (r = − 0.47, P < 0.05). Further, a relationship was observed between IntraMAT CSA and change in SWV and fascicle length from NP to DF15 (r = − 0.47 and r = 0.59, P < 0.05); whereas no relationship was observed between changes in fascicle length and muscle SWV (r = − 0.23, P = 0.33). These results may indicate biomechanical and/or physiological associations between IntraMAT CSA and passive muscle stiffness.

Abstract This study used ultrasound shear wave elastography (SWE) to revalidate whether surface electromyographic (EMG) electrodes placed on the oblique externus abdominis (OE) can detect only the OE activity without the confounding activity of the underlying oblique internus abdominis (OI). During left and right trunk rotations, the EMG activity was acquired using surface EMG electrodes placed on the right OE. Shear wave velocity (Vs) values of the right OE and OI were acquired using SWE. The EMG activity during the left and right trunk rotations significantly increased as the level of exertion increased (25%, 50%, 75%, and 100% of the one‐repetition maximum [1RM]). The Vs of the right OE was significantly different only between 25% and 75% 1RM in the right trunk rotation, but significantly increased from 25% to 75% 1RM during the left trunk rotation. The Vs of the right OI during the right trunk rotation significantly increased with increased levels of exertion, except between 50% and 75% 1RM. The results for the Vs of the OE and OI in the right trunk rotation suggest that surface EMG electrodes placed on the OE would detect not only the antagonistic OE activity but also the agonistic OI activity.

Long-distance runners require aerobic capacity as well as sprinting ability for superior performance; however, the factors which determine the sprinting ability of long-distance runners remain undetermined. Therefore, the purpose of our study was to examine the association between thigh muscle size and sprinting ability in national-level male long-distance runners. Nineteen male long-distance runners with 5000 m personal-best times of 13:12.63-14:14.87 participated in this study, and transaxial images of their right thighs were collected using magnetic resonance imaging. The cross-sectional areas of the quadriceps femoris, hamstrings, and adductor muscles were calculated from the transaxial images at 30%, 50%, and 70% of the distance from the greater trochanter to the lower edge of the femur; these areas were normalized by body mass. Sprint times for 100 m and 400 m were recorded on an all-weather track. The results revealed positive correlations between the normalized cross-sectional areas of the quadriceps femoris at 50% and 70% of the thigh length and the 100 m (r = 0.666, p = 0.002 and r = 0.531, p = 0.019, respectively) and 400 m sprint times (r = 0.769, p < 0.001 and r = 0.580, p = 0.009, respectively); hence, the larger the quadriceps, the slower the sprint speed. However, no association was found between the normalized cross-sectional areas of the hamstrings or adductor muscles and sprinting performance. Therefore, running motions which activate the quadriceps femoris much more than the hamstrings and adductor muscles should be avoided by national-level long-distance runners.

Purpose : Inspiratory muscle strength training (IMST) can improve exercise performance. Increased maximal inspiratory mouth pressure (MIP) could be beneficial for swimmers to enhance their performance. This study aimed to clarify the effect of high-intensity IMST for 6 weeks on MIP and swimming performance in highly trained competitive swimmers. Methods: Thirty male highly trained competitive swimmers were assigned to high-intensity IMST (HI; n = 10), moderate-intensity IMST (MOD; n = 10), and control (n = 10) groups. The 6-week IMST intervention comprised twice daily sessions for 6 d/wk at inspiratory pressure threshold loads equivalent to 75% MIP (HI) and 50% MIP (MOD). Before and after the intervention, MIP and swimming performance were assessed. Swimming performance was evaluated in free and controlled frequency breathing 100-m freestyle swimming time trials in a 25-m pool. For controlled frequency breathing, participants took 1 breath every 6 strokes. Results: The MIP values after 2 and 6 weeks of IMST in the HI and MOD groups were significantly higher than those before IMST ( P = .0001). The magnitudes of the MIP increases after 6 weeks of IMST did not differ between the HI (13.4% [8.7%]) and MOD (13.1% [10.1%]) groups ( P = .44). The 100-m freestyle swimming times under the controlled frequency condition were significantly shorter after IMST than those before IMST in both the HI ( P = .046) and MOD ( P = .042) groups. Conclusions: Inspiratory pressure threshold load equivalent to 50% MIP could be sufficient to improve MIP and swimming performance under the controlled frequency breathing condition in highly trained competitive swimmers.

Passive muscle stiffness is positively associated with explosive performance. Drop jump training may be a strategy to increase passive muscle stiffness in the lower limb muscles. Therefore, the purpose of this study was to examine the effect of 8-week drop jump training on the passive stiffness in the plantar flexor muscles and the association between training-induced changes in passive muscle stiffness and explosive performance. This study was a randomized controlled trial. Twenty-four healthy young men were divided into two groups, control and training. The participants in the training group performed drop jumps (five sets of 20 repetitions each) 3days per week for 8weeks. As an index of passive muscle stiffness, the shear moduli of the medial gastrocnemius and soleus were measured by shear wave elastography before and after the intervention. The participants performed maximal voluntary isometric plantar flexion at an ankle joint angle of 0° and maximal drop jumps from a 15cm high box. The rate of torque development during isometric contraction was calculated. The shear modulus of the medial gastrocnemius decreased for the training group (before: 13.5±2.1kPa, after: 10.6±2.1kPa); however, such a reduction was not observed in the control group. There was no significant group (control and training groups)×time (before and after the intervention) interaction for the shear modulus of the soleus. The drop jump performance for the training group improved, while the rate of torque development did not change. Relative changes in these measurements were not correlated with each other in the training group. These results suggest that drop jump training decreases the passive stiffness in the medial gastrocnemius, and training-induced improvement in explosive performance cannot be attributed to change in passive muscle stiffness.

Although the influence of the series elastic element of the muscle-tendon unit on jump performance has been investigated, the corresponding effect of the parallel elastic element remains unclear. This study examined the relationship between the resting calf muscle stiffness and drop jump performance. Twenty-four healthy men participated in this study. The shear moduli of the medial gastrocnemius and the soleus were measured at rest as an index of muscle stiffness using ultrasound shear wave elastography. The participants performed drop jumps from a 15 cm high box. The Spearman rank correlation coefficient was used to examine the relationships between shear moduli of the muscles and drop jump performance. The medial gastrocnemius shear modulus showed a significant correlation with the drop jump index (jump height/contact time) (r = 0.414, P = 0.044) and jump height (r = 0.411, P = 0.046), but not with contact time (P > 0.05). The soleus shear modulus did not correlate with these jump parameters (P > 0.05). These results suggest that the resting medial gastrocnemius stiffness can be considered as one of the factors that influence drop jump performance. Therefore, increase in resting muscle stiffness should enhance explosive athletic performance in training regimens.

BACKGROUND: Inspiratory muscle fatigue (IMF) may impair performance in a subsequent exercise. A few studies have reported that IMF decreased swimming performance in submaximal intensity or severe intensity domain. However, the impact of IMF on high-intensity short-duration swimming is not clear. The purpose of this study was to clarify the effect of preinduced IMF on extreme intensity domain swimming. METHODS: Seven male competitive swimmers swam two 100-meter all-out front crawl swimming trials with and without preinduced IMF. Maximal inspiratory and expiratory mouth pressure (PImax and PEmax, respectively) was used as indicators of inspiratory and expiratory muscle strength before and after swimming. and stroke parameters during swimming were measured. IMF was achieved by having the subjects breathe against an inspiratory pressure threshold load while generating 40% of their predetermined PImax for 10 minutes. RESULTS: After the induction of IMF, swimming time (55.94 +/- 1.15 s) was significantly slower compared with that in control swimming without IMF (54.09 +/- 0.91 s) (P<0.05). During swimming followed IMF, a significant decrease in stroke rate and a significant increase in stroke length were observed in the latter half of the 100-meter swimming trial. In addition, the sense of dyspnea was significantly higher in swimming in the IMF condition than in control condition. CONCLUSIONS: IMF prior to swimming negatively affects swimming performance in the extreme intensity domain. It is suggested that due to the dual use of respiration and generate propulsion in accessory respiratory muscles, IMF affected swimmers' ability to maintain swimming velocity.

The force–length relation of the skeletal muscles is an important factor influencing the joint torque at a given joint angle. We aimed to clarify the relationship between the resting sarcomere length and knee joint angle in the vastus intermedius (VI) and to compare it with that of the vastus lateralis (VL). The left and right legs were fixed at knee joint angles of 0° and 90°, respectively, in seven cadavers (age at the time of death: 70–91 years). Muscle tissues were dissected by necropsy of the VL and the VI, and electron microscopy images were obtained to calculate the sarcomere length. At knee joint angles of 0° and 90°, the VL sarcomere length was 2.28 ± 0.49 μm and 2.30 ± 0.48 μm, respectively, and the VI sarcomere length was 2.19 ± 0.35 μm and 2.46 ± 0.53 μm, respectively, with a significant difference between the two (p = 0.028). The magnitude of sarcomere length changes with knee joint angle changes was significantly greater for the VI (0.27 ± 0.20 μm) than for the VL (0.02 ± 0.09 μm) (p = 0.009). Thus, knee joint angle changes may affect the passive and active tension produced by the VI more than those produced by the VL.

The purpose of this study was to elucidate the effects of hypoxia on deoxygenation and neuromuscular activation in synergistic quadriceps femoris (QF) muscles (i.e., the rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis) during submaximal intermittent knee extension. Ten healthy men performed isometric intermittent knee extension exercises with the right leg at 50% of maximal voluntary contraction for 3 min while inhaling a normoxic [inspired oxygen (O2) fraction = 0.21] or hypoxic (inspired O2 fraction = 0.10–0.12) gas mixture. Muscle deoxygenation was measured by tissue O2 saturation (StO2), and neuromuscular activation by root mean square (RMS) of the surface electromyographic signals, from individual muscles of the QF using near-infrared spectroscopy and surface electromyography. StO2 was decreased more in hypoxia than normoxia during the exercises, and there was a greater increase in RMS during intermittent knee extension in hypoxia than normoxia in individual muscles of the QF. There were no differences in the ratios of StO2 and RMS in hypoxia compared with normoxia between individual muscles of the QF. These findings suggest that submaximal, isometric, and intermittent exercises in hypoxic conditions enhanced muscle oxygen consumption and muscle activity similarly for synergistic muscles.

This study aimed to elucidate changes in diaphragm and accessory inspiratory muscle (sternocleidomastoid (SCM) muscle and intercostal muscle (IC)) function after a 6-week training program. Nineteen male elite collegiate swimmers were assigned to either a control group (n = 9) or training group (n = 10). The subjects in the training group performed 30 maximum inspirations at a load resistance of 50% of maximum inspiratory mouth pressure (PImax) using an inspiratory muscle training device. These were conducted twice per day and 6 days per week. At baseline and after 6 weeks, PImax, shear modulus of the diaphragm, and electromyograms (EMG) of the SCM and IC during a maximal inspiratory maneuver were evaluated. Relative change in PImax was greater in the training group than in controls. The shear modulus during a PImax maneuver had increased significantly in both groups after 6 weeks. EMG amplitudes of the SCM increased in the training group after 6 weeks, but not in the control group. EMG amplitudes of the IC did not change after 6 weeks in either group. These results suggest that 6-week inspiratory resistive training significantly improves the activation of the SCM, which could be one of the major mechanisms behind increases in inspiratory muscle strength after resistive training. Novelty Six-week inspiratory resistive training increased diaphragm stiffness during maximal inspiration maneuver. Six-week inspiratory resistive training increased electromyogram amplitudes of the sternocleidomastoid during maximal inspiration maneuver.