Can Eccentric-only Resistance Training Decrease Passive Muscle Stiffness while Increasing Size and Strength of Hamstrings?

PURPOSE: Resistance training may be empirically believed to increase passive muscle stiffness. Meanwhile, a recent study showed that the passive stiffness of a specific hamstring muscle acutely decreased after eccentric-only resistance exercise at long muscle lengths with a long contraction duration (LL). To extend this finding, the present study investigated the chronic effects of eccentric-only resistance training with LL at different weekly frequencies on the passive stiffness of the biarticular hamstring muscles. METHODS: Thirty-six healthy young males were assigned into two training groups with two and three weekly sessions (W2 and W3, n = 12, respectively) and a control group (CON, n = 12). The participants in both training groups performed eccentric-only stiff-leg deadlift at 50-100% of exercise range of motion (0% = upright position) with 5 s per repetition for 10 weeks. Before and after the intervention period, the shear moduli of the biarticular hamstring muscles, maximal voluntary isometric torque of knee flexion, and volumes of the individual hamstring muscles were measured. RESULTS: In W3, the shear modulus of the semimembranosus (-11.4%) significantly decreased, whereas those of the other biarticular muscles did not change. There were no significant changes in the shear moduli of the biarticular hamstring muscles in W2 or CON. The isometric torque (20.3 and 26.2%, respectively) and semimembranosus volume (5.7% and 7.4%, respectively) were significantly increased in W2 and W3. CONCLUSIONS: Passive stiffness of a specific muscle could be chronically decreased when eccentric-only resistance training with LL is performed at a relatively high weekly frequency with a high total training volume. Our training modality may be a promising strategy for decreasing passive muscle stiffness while increasing muscular strength and size.

Effect of CO2 and H2 gas mixture in cold water immersion on recovery after eccentric loading.

Background: The findings of previous studies support the efficacy of cold water immersion (CWI) with carbon dioxide (CO2) in enhancing muscle blood flow and maintaining aerobic performance efficiency. We hypothesize that the addition of hydrogen gas (H2), known for its antioxidant properties and role in inflammation regulation, to C-CWI can enhance recovery after eccentric exercise. Subjects: and Methods: Thirty-four healthy subjects performed a knee-extensor eccentric exercise. They were randomly allocated into four groups: control, CWI, CO2-rich CWI (C-CWI), and CO2 + H2 gas mixture CWI (CH-CWI). In the three CWI groups, all subjects were immersed in the appropriate bath at 20 °C for 20 min immediately after 60 repetitions of eccentric exercise. Before exercise and after 48 h of recovery, the subjects' maximal voluntary isometric contraction torque (MVC-ISO), maximal voluntary concentric (MVC-CON) contraction torque, countermovement jump (CMJ) height, knee flexion range of motion (ROM), muscle soreness, and muscle thickness were measured. Results: In the CH-CWI group only, the MVC-ISO, CMJ height, and ROM did not decrease significantly post-exercise, whereas all of these decreased in the other three groups. Muscle soreness at palpation, contraction, and stretching significantly increased post-exercise in all groups. Echo intensity and tissue hardness did not increase significantly in the CH-CWI group. Conclusions: CH-CWI stimulated recovery from impairments in MVC-ISO torque, CMJ height, knee-flexion ROM, tissue hardness, and echo intensity. These findings indicate that CH-CWI can promote recovery after eccentric exercise.

Synergistic Dominance Induced by Hip Extension Exercise Alters Biomechanics and Muscular Activity During Sprinting and Suggests a Potential Link to Hamstring Strain.

ABSTRACT: Iguchi, J, Hojo, T, Fujisawa, Y, Kuzuhara, K, Yanase, K, Hirono, T, Koyama, Y, Tateuchi, H, and Ichihashi, N. Synergistic dominance induced by hip extension exercise alters biomechanics and muscular activity during sprinting and suggests a potential link to hamstring strain. J Strength Cond Res 37(9): 1770-1776, 2023-Hamstring strain is likely to occur during the late swing phase or the first half of the stance phase in sprinting. During the late swing phase, the hamstrings and gluteus maximus (Gmax) contract eccentrically to decelerate the lower limb. We hypothesized that, when the Gmax becomes dysfunctional because of delayed onset muscle soreness (DOMS), the hamstring workload is increased (i.e., there is synergetic dominance), which could lead to an increased risk of strain. A total of healthy 15 male undergraduate or graduate students (age 23.1 ± 1.28 years) were recruited to perform exercises and maximal sprints. On day 1, before subjects performing DOMS-causing exercises, and on day 3, while subjects were experiencing DOMS in the Gmax, lower-limb biomechanical and muscle activity data were recorded using a motion analysis system and electromyography (EMG), respectively. Data were analyzed and compared between day 1 and day 3. Hip flexion angle on day 3 was significantly lower than that on day 1, but the opposite was true for the knee flexion angle (P < 0.05). Vastus medialis (VM), biceps femoris (BF), and Gmax muscle activities on day 3 were significantly higher than those on day 1 (P < 0.05). Peak propulsive forces on day 3 were significantly higher than those on day 1 (P < 0.05). Kinematic changes such as decreased hip flexion angle and EMG changes such as increased BF EMG activity on day 3 to compensate for the loss of function of the Gmax may potentially increase the risk of hamstring strain.

The field study about the effects of artificial CO2-rich cool-water immersion after outdoor sports activity in a hot environment.

Background/objective: In our previous laboratory experiment (room temperature of 25 °C), CO2-rich cool-water immersion (CCWI) suppressed subjects' core body temperature even during repeated exercise. It is unclear whether the suppression of body temperature elevation would also continue after CCWI in a hot outdoor environment. Herein we investigated the thermal effects of CCWI after regular exercise training in heat on subjects' core temperature (Tcore), three skin temperatures (Tskin), heart rate (HR), and the rate of perceived ice (RPI). Methods: Thirty-six subjects (25 males, 11 females) were randomly allocated into three groups (CCWI, CWI, and control). After training at their competitive clubs, each subject was immersed up to the chest in CCWI or CWI at 20 °C for 20 min, followed by a 60-min recovery period. Tcore, Tskin, HR, and RPI were measured at the initial rest, the end of immersion, and every 10 min during the recovery period. Results: Compared to the control, the CCWI subjects' Tcore was significantly lower at 50-60 min after the end of immersion (p < 0.05). Tskin at abdominal and lower-leg regions during the recovery period was maintained at significantly lower values in the CWI and CCWI groups versus control (p < 0.05). The CCWI subjects maintained lower Tskin for a longer time than the CWI subjects. Conclusions: These findings indicate that CCWI suppresses the rise in body temperatures more than CWI, even in a hot environment, suggesting that CCWI may be a more effective countermeasure against increasing body temperature in a hot outdoor environment.

Acute changes in passive stiffness of the individual hamstring muscles induced by resistance exercise: effects of muscle length and exercise duration.

PURPOSE: A previous study revealed that resistance exercise with eccentric contraction and a wide range of motion (ROM) can acutely decrease muscle stiffness of a specific muscle. To explore further approaches to decrease the stiffness, we examined the acute changes in passive stiffness of the individual hamstring muscles after eccentric-only resistance exercise with different combinations of muscle lengths and exercise durations. METHODS: Thirteen healthy young male participants performed three sessions of eccentric-only exercises that comprised stiff-leg deadlift with different muscle lengths and exercise durations (duration per repetition × the total number of repetitions) on separate days as follows: (1) short muscle lengths with a short duration (SS); (2) long muscle lengths with a short duration (LS); and (3) long muscle lengths with a long duration (LL). Maximal joint ROM, passive torque, shear modulus of each hamstring muscle, and maximal isometric torque of knee flexion were measured before, and at 3, 30, and 60 min after each session. RESULTS: The shear modulus of the semimembranosus was significantly lower at 3 min post-exercise (129.8 ± 22.7 kPa) than at pre-exercise (140.5 ± 19.1 kPa, p < 0.01) in LL, but not in SS or LS. No significant differences were observed in the shear moduli of the biceps femoris long head or semitendinosus between pre-exercise and 3 min post-exercise in any session. CONCLUSION: The combination of long muscle lengths and a long duration during eccentric-only resistance exercise is important to immediately decrease the stiffness (shear modulus) of a specific muscle.

Side-To-Side Difference in Electromyographic Activity of Abdominal Muscles during Asymmetric Exercises.

A side-to-side difference in the muscle size of the rectus abdominis has been suggested to increase the strain injury risk. Attenuating the difference in size of the rectus abdominis may decrease the injury risk. To explore ways to highly activate one side of the rectus abdominis, we aimed to clarify the activity levels of both sides of the muscle during asymmetric abdominal exercises. Fifteen male sprinters performed the following five asymmetric exercises for the right and left sides: (i) sit-up twist, (ii) oblique leg raise, (iii) side bridge, (iv) side bridge roll out with the elbow, and (v) side bridge roll out with the foot. Side bridge roll out with the elbow and that with the foot were performed using a wheeled platform. During the exercises, electromyographic signals were recorded bilaterally from the upper, central, and lower portions of the rectus abdominis. We calculated the root mean square of electromyograms during the concentric and eccentric phases of the exercises and normalized to that during maximal voluntary contractions. In all portions of the rectus abdominis, the root mean squares of electromyograms were significantly higher in the moving side than in the non-moving side during the concentric and eccentric phases of the side bridge, the side bridge roll out with the elbow and that with the foot (all p < 0.01), but not in sit-up twist or oblique leg raise. The root mean squares of electromyograms of all portions of the rectus abdominis in the moving side were significantly higher in the side bridge roll out with the elbow and that with the foot than in the side bridge during both phases (all p < 0.01). The results suggest that the application of the wheeled platform to side bridge is useful to highly activate one side of the rectus abdominis.

The Acute Effects of a Single Dose of Molecular Hydrogen Supplements on Responses to Ergogenic Adjustments during High-Intensity Intermittent Exercise in Humans.

This research examined the effects of single-dose molecular hydrogen (H2) supplements on acid-base status and local muscle deoxygenation during rest, high-intensity intermittent training (HIIT) performance, and recovery. Ten healthy, trained subjects in a randomized, double-blind, crossover design received H2-rich calcium powder (HCP) (1500 mg, containing 2.544 µg of H2) or H2-depleted placebo (1500 mg) supplements 1 h pre-exercise. They performed six bouts of 7 s all-out pedaling (HIIT) at 7.5% of body weight separated by 40 s pedaling intervals, followed by a recovery period. Blood gases' pH, PCO2, and HCO3- concentrations were measured at rest. Muscle deoxygenation (deoxy[Hb + Mb]) and tissue O2 saturation (StO2) were determined via time-resolved near-infrared spectroscopy in the vastus lateralis (VL) and rectus femoris (RF) muscles from rest to recovery. At rest, the HCP group had significantly higher PCO2 and HCO3- concentrations and a slight tendency toward acidosis. During exercise, the first HIIT bout's peak power was significantly higher in HCP (839 ± 112 W) vs. Placebo (816 ± 108 W, p = 0.001), and HCP had a notable effect on significantly increased deoxy[Hb + Mb] concentration during HIIT exercise, despite no differences in heart rate response. The HCP group showed significantly greater O2 extraction in VL and microvascular (Hb) volume in RF during HIIT exercise. The HIIT exercise provided significantly improved blood flow and muscle reoxygenation rates in both the RF and VL during passive recovery compared to rest in all groups. The HCP supplement might exert ergogenic effects on high-intensity exercise and prove advantageous for improving anaerobic HIIT exercise performance.

Acute changes in passive stiffness of the individual hamstring muscles induced by resistance exercise: effects of contraction mode and range of motion.

PURPOSE: Recent studies raise an interesting possibility that resistance exercise also decreases passive muscle stiffness, as does stretching exercise. However, little is known about how program variables of resistance exercise acutely influence muscle stiffness. We aimed to examine the acute changes in passive stiffness of the individual hamstring muscles after resistance exercises using different combinations of contraction modes and ranges of motion (ROMs). METHODS: Thirteen healthy young male participants performed three sessions of resistance exercises that comprised stiff-leg deadlift with different contraction modes and exercise ROMs on separate days as follows: (1) eccentric contractions with a wide exercise ROM (EW); (2) eccentric contractions with a narrow exercise ROM (EN); and (3) concentric contractions with a wide exercise ROM (CW). Maximal joint ROM, passive torque, shear modulus of the individual hamstring muscles, and maximal isometric torque of knee flexion were measured before and 3 min, 30 min, and 60 min after completing each session. RESULTS: The shear modulus of the semimembranosus was significantly lower at 3 min post-exercise (121.8 ± 16.0 kPa) than at pre-exercise (129.0 ± 18.9 kPa, p = 0.021, r = 0.45) in EW, but not in EN or CW. There were no significant changes in the shear moduli of the biceps femoris long head or the semitendinosus at any timepoint in any exercise protocols. CONCLUSIONS: The present results suggest that the combination of eccentric contraction and wide ROM during resistance exercise has the potential to acutely decrease passive stiffness (shear modulus) of a specific muscle.

Anaerobic performance after 3-day consecutive CO2-rich cold-water immersion in physically active males.

Background Objective: We investigated the effects of a 3-day consecutive CO2-rich cold (20 °C) water immersion (CCWI) following a high-intensity intermittent test (HIIT) on subjects' sublingual temperature (Tsub), blood lactate ([La]b), and heart rate (HR) compared to cold (20 °C) tap-water immersion (CWI) or passive recovery (PAS). Methods: Thirty-two subjects were randomly allocated into three groups (CCWI, CWI, and PAS), each of which completed 4 consecutive days of cycling experiments. HR, Tsub, and [La]b were recorded on each day of exercise testing (immersion from Day 1 to Day 3 and Day 4). HIIT consisted of 8 sets of 20-sec maximum exercise at an intensity of 120% of VO2max with 10-sec passive rest. The mean and peak power, and peak pedal repetitions (PPR) within HIIT were averaged and the decline in PPR (ΔPPR) from Day 1 to Day 4 was measured. Results: In CCWI and CWI, HR declined significantly following each immersion, with CCWI showing the larger reduction (p < 0.001). At Day 2, CCWI showed a significantly lower [La]b compared to PAS (p < 0.01). The changes in mean and peak power from Day 1 to Day 4 did not differ among the groups (p = 0.302). ΔPPR of HIIT was significantly correlated with the HR and [La]b values after immersions (ΔPPR-HR: r2 = 0.938, p < 0.001, ΔPPR-[La]b: r2 = 0.999, p < 0.001). Conclusions: These findings indicate that CCWI is a promising intervention for maintaining peak performance in high-intensity intermittent exercise, which is associated with a reduction in [La]b and HR.

Effects of artificial CO2-rich cold-water immersion on repeated-cycling work efficiency.

We investigated the acute effects of cold-water immersion (20°C) with higher CO2 concentration (CCWI) following a high-intensity Wingate anaerobic exercise test (WAnT) on subjects' sublingual temperature (Tsub), blood lactate ([La]b), heart rate (HR), and aerobic cycling work efficiency (WE) compared to cold tap-water immersion (20°C; CWI) and passive recovery (PAS). Fifteen subjects completed three testing sessions at 1-week intervals. Each trial consisted of a first WE and WAnT, and a 20-min recovery intervention (randomized: CCWI, CWI, and PAS) before repeating a second WE and WAnT. The WE was measured by the metabolic demand during 50% V.O2max exercise. HR, Tsub, and [La]b were recorded throughout the testing sessions. There was a significant decline in the WE from 1st bout to 2nd bout at each recovery intervention. The WAnT was also significantly reduced at 2nd bout. Significantly reduced [La]b was achieved at CCWI compared to PAS, but not to the CWI. Likewise, the reduction in HR following immersion was the largest at CCWI compared to the other conditions. These findings indicate that CCWI is an effective intervention for maintaining repeated cycling work efficiency, which might be associated with reduced [La]b and HR.

Application of Molecular Hydrogen as an Antioxidant in Responses to Ventilatory and Ergogenic Adjustments during Incremental Exercise in Humans.

We investigated effects of molecular hydrogen (H2) supplementation on acid-base status, pulmonary gas exchange responses, and local muscle oxygenation during incremental exercise. Eighteen healthy, trained subjects in a randomized, double-blind, crossover design received H2-rich calcium powder (HCP) (1500 mg/day, containing 2.544 µg/day of H2) or H2-depleted placebo (1500 mg/day) for three consecutive days. They performed cycling incremental exercise starting at 20-watt work rate, increasing by 20 watts/2 min until exhaustion. Breath-by-breath pulmonary ventilation (V˙E) and CO2 output (V˙CO2) were measured and muscle deoxygenation (deoxy[Hb + Mb]) was determined via time-resolved near-infrared spectroscopy in the vastus lateralis (VL) and rectus femoris (RF). Blood gases' pH, lactate, and bicarbonate (HCO3-) concentrations were measured at rest and 120-, 200-, and 240-watt work rates. At rest, the HCP group had significantly lower V˙E, V˙CO2, and higher HCO3-, partial pressures of CO2 (PCO2) versus placebo. During exercise, a significant pH decrease and greater HCO3- continued until 240-watt workload in HCP. The V˙E was significantly lower in HCP versus placebo, but HCP did not affect the gas exchange status of V˙CO2 or oxygen uptake (V˙O2). HCP increased absolute values of deoxy[Hb + Mb] at the RF but not VL. Thus, HCP-induced hypoventilation would lead to lower pH and secondarily impaired balance between O2 delivery and utilization in the local RF during exercise, suggesting that HCP supplementation, which increases the at-rest antioxidant potential, affects the lower ventilation and pH status during incremental exercise. HPC induced a significantly lower O2 delivery/utilization ratio in the RF but not the VL, which may be because these regions possess inherently different vascular/metabolic control properties, perhaps related to fiber-type composition.

Seasonal Changes in Anthropometric, Physiological, Nutritional, and Performance Factors in Collegiate Rowers.

Iguchi J, Kuzuhara, K, Katai, K, Hojo, T, Fujisawa, Y, Kimura, M, Yanagida, Y, and Yamada, Y. Seasonal changes in anthropometric, physiological, nutritional, and performance factors in collegiate rowers. J Strength Cond Res 34(11): 3225-3231, 2020-Well-controlled seasonal distribution of training intensity seems to be an important variable for endurance athletes' success as competitors and for avoidance of overtraining. The aim of this study was to examine the interrelationships of training distribution, body composition, energy intake/expenditure, and rowing ergometer performance throughout the 2012-2013 season. In this study of 15 collegiate male rowers, most of whom started rowing during their time at the university, we divided the 2012-2013 season (total 37 weeks) into 3 phases (off-season, December to mid-March, 16 weeks; pre-season, late March-April, 5 weeks; and in-season, May-August, 16 weeks) and analyzed the transition of 2,000-m rowing ergometer time, training intensity/volume, body composition (body mass and body fat), and energy intake/expenditure in each phase. There were significant main effects of the training time by the intensities; 2,000-m rowing ergometer time; energy expenditure; and protein, fat, and carbohydrate intake across the seasons (p < 0.05). Two findings were particularly important. First, on-water high-intensity training, especially for inexperienced rowers, may contribute to improvement of 2,000-m rowing ergometer performance. Second, higher intake of carbohydrate, and to a lesser degree, protein, is necessary for optimal training adaptation (e.g., increase of muscle glycogen content), and results in better 2,000-m performance on the rowing ergometer. Also, those findings may be beneficial to the coaches who are interested in designing the well-controlled seasonal training program, which is especially intended to improve the 2,000-m rowing ergometer performance as well as avoidance of overtraining.

Application of carbon dioxide to the skin and muscle oxygenation of human lower-limb muscle sites during cold water immersion.

BACKGROUND: Cold therapy has the disadvantage of inducing vasoconstriction in arterial and venous capillaries. The effects of carbon dioxide (CO2) hot water depend mainly on not only cutaneous vasodilation but also muscle vasodilation. We examined the effects of artificial CO2 cold water immersion (CCWI) on skin oxygenation and muscle oxygenation and the immersed skin temperature. SUBJECTS AND METHODS: Fifteen healthy young males participated. CO2-rich water containing CO2 >1,150 ppm was prepared using a micro-bubble device. Each subject's single leg was immersed up to the knee in the CO2-rich water (20 °C) for 15 min, followed by a 20-min recovery period. As a control study, a leg of the subject was immersed in cold tap-water at 20 °C (CWI). The skin temperature at the lower leg under water immersion (Tsk-WI) and the subject's thermal sensation at the immersed and non-immersed lower legs were measured throughout the experiment. We simultaneously measured the relative changes of local muscle oxygenation/deoxygenation compared to the basal values (Δoxy[Hb+Mb], Δdeoxy[Hb+Mb], and Δtotal[Hb+Mb]) at rest, which reflected the blood flow in the muscle, and we measured the tissue O2 saturation (StO2) by near-infrared spectroscopy on two regions of the tibialis anterior (TA) and gastrocnemius (GAS) muscles. RESULTS: Compared to the CWI results, the Δoxy[Hb+Mb] and Δtotal[Hb+Mb] in the TA muscle at CCWI were increased and continued at a steady state during the recovery period. In GAS muscle, the Δtotal[Hb+Mb] and Δdeoxy[Hb+Mb] were increased during CCWI compared to CWI. Notably, StO2values in both TA and GAS muscles were significantly increased during CCWI compared to CWI. In addition, compared to the CWI, a significant decrease in Tsk at the immersed leg after the CCWI was maintained until the end of the 20-min recovery, and the significant reduction continued. DISCUSSION: The combination of CO2 and cold water can induce both more increased blood inflow into muscles and volume-related (total heme concentration) changes in deoxy[Hb+Mb] during the recovery period. The Tsk-WI stayed lower with the CCWI compared to the CWI, as it is associated with vasodilation by CO2.

Ground golf-induced changes in the blood pressure of healthy elderly people.

BACKGROUND: Ground golf is a popular sport among the elderly in Japan. Several types of exercise can reduce the body's mean arterial pressure (MAP), but little is known about how ground golf affects the MAP. We investigated the effects of ground golf on the MAP and the oxygen uptake ([Formula: see text]) in a healthy elderly population. PARTICIPANTS AND METHODS: Thirteen elderly Japanese people (3 males and 10 females, mean age of 66 years) participated. All participants played 8 holes of ground golf 6 times, as game (G)1 to G6. The MAP, heart rate (HR), and [Formula: see text] were measured at rest and every 5 min during each game. RESULTS: A linear trend analysis revealed that participants' MAP values progressively decreased as each game proceeded with marginal differences (p = 0.054). There were no significant differences in HR between at rest and any of the games. The [Formula: see text] during the games (except for G6) were significantly higher than that at-rest (p < 0.05). The resting MAP values were negatively associated with the ground golf-induced changes in MAP (r = 0.786, p = 0.001). The participants with greater changes in [Formula: see text] during the games showed significantly greater reductions in MAP (r = 0.276, p = 0.043). CONCLUSIONS: Playing ground golf reduced the participants' MAP and increased their [Formula: see text]. Participants with higher resting MAP experienced greater reductions in MAP by playing ground golf, which suggests that ground golf can be a useful recreational sport for the elderly.

In-match physical demands on elite Japanese rugby union players using a global positioning system.

OBJECTIVES: Our aim of this study was to quantify the physical demands of elite rugby union players by each position as a step towards designing position-specific training programme using a Global Positioning System/accelerometer system. METHODS: This study was performed as a retrospective observational study. Data were obtained from 45 official matches. The sample size used for the analysis was 298. The per-match total distances, accelerations and impacts were calculated and statistically compared for the forwards and backs and for individual positions. RESULTS: Total distances for the forwards and backs were 5731.1±507.8 and 6392.1±646.8 m, respectively. The high-velocity running distances (>18.0 km/hour) covered by the forwards and backs were 317.4±136.9 and 715.0±242.9 m, respectively. The number of accelerations (>1.5 m/s2) for the forwards and backs were 76.3±18.9 and 100.8±19.6 times, respectively, and the number of high impacts (>10 g) were 48.0±46.9 and 35.6±28.3 times for the forwards and backs, respectively. All characteristics were significantly different between the forwards and backs (p<0.05). The per-position characteristics were also calculated. Within the backs, scrum half (SH) and wingers (WTBs) covered high-velocity running significantly higher distance than fly-half (SH d=2.571, WTBs d=1.556) and centres (SH d=1.299, WTBs d=0.685) (p<0.05). CONCLUSION: By clarifying the physical demands according to the positions, it will be possible to create optimised position-specific training programmes.

Evaluation of a Novel Device for Assessing Ballet Dancers' Functional Turnout.

Despite various approaches to measuring ballet dancers' turnout, no standardized method for doing so has yet been estab- lished. Here a newly designed rotational goniometer (RGM) for assessing ballet dancers' functional turnout is evaluated. Twenty experienced female ballet dancers participated in the study. Measurements of the dancers' turnout were taken three times in each of the following conditions: 1. while standing on the RGM device (RGMT); 2. as if the participant was in a ballet class (CT); and 3. performing an active external rotation of the lower extremities in the supine position (AT). The angles obtained in the three trials in each condition were averaged and the results of the three conditions were compared. The mean angle of RGMT (RGMTangle: 103.89° ± 15.2°) was significantly smaller than those of the CT (CTangle: 128.7° ± 15.1°) and AT (ATangle: 110.09° ± 17.6°) conditions (p < 0.05 and p < 0.01, respectively). The greatest angle (i.e., the CTangle) is influenced by both friction and weightbearing. The ATangle is released from weightbearing, unlike the RGMTangle. Positive correlations were revealed between the RGMTangle and the ATangle (r = 0.78, p < 0.01) and between the RGMTangle and the CTangle (r = 0.57, p = 0.05). These findings demonstrate that the novel RGM device, characterized by elimination of friction and full weightbearing, is useful for assessing ballet dancers' functional turnout.

Characteristics of cardiovascular responses to an orthostatic challenge in trained spinal cord-injured individuals.

BACKGROUND: We investigated cardiovascular responses to an orthostatic challenge in trained spinal cord-injured (SCI) individuals compared to able-bodied (AB) individuals. METHODS: A total of 23 subjects participated, divided into three groups: seven were trained as spinal cord-injured (Tr-SCI) individuals, seven were able-bodied individuals trained as runners (Tr-AB), and nine were untrained able-bodied individuals (UnTr-AB). We measured the cardiovascular autonomic responses in all three groups during each 5-min head-up tilt (HUT) of 0°, 40°, and 80°. Stroke volume (SV), heart rate (HR), and cardiac output (Qc) as cardiovascular responses were measured by impedance cardiography. Changes in deoxyhemoglobin (∆[HHb]) and total hemoglobin (∆[Hbtot]) concentrations of the right medial gastrocnemius muscle were measured using near-infrared spectroscopy (NIRS). RESULTS: As the HUT increased from 0° to 80°, Tr-SCI group showed less change in SV at all HUT levels even if HR increased significantly. Mean arterial pressure (MAP) also did not significantly increase as tilting increased from 0° to 80°. Regarding peripheral vascular responses, the alterations of ∆[Hbtot] from 0° to 80° were less in Tr-SCI group compared to AB individuals. CONCLUSION: There is a specific mechanism whereby blood pressure is maintained during a HUT in Tr-SCI group with the elicitation of peripheral vasoconstriction and the atrophy of the vascular vessels in paraplegic lower limbs, which would be associated with less change in SV in response to an orthostatic challenge.

Influence of Age on Cardiorespiratory Kinetics During Sinusoidal Walking in Humans.

We sought to determine the influence of age on cardiorespiratory kinetics during sinusoidal walking in two groups: 13 healthy young subjects (YG; 7 men and 6 women, age 21 ± 2 years) and 15 healthy elderly subjects (ELD; 9 men and 6 women, age 67 ± 5 years). A treadmill's speed was sinusoidally changed between 3 and 6 km h-1 in the YG and between 3 and 5 km h-1 in the ELD during periods of 1, 2, 5, and 10 min, and in a stepwise manner. We compared the groups' heart rate (HR), ventilation ( V˙E), and gas exchange (CO2 output ( V˙ CO2) and O2 uptake ( V˙ O2)) responses. We determined the phase shift (PS) and the normalized amplitude (Amp) ratio of these kinetics in relation to the sinusoidal change in walking speed in response to the magnitude from the maximum to minimum speeds as revealed by a Fourier analysis in all cardiorespiratory variables. Both the Amp ratio and PS in the V˙E, V˙ CO2, and V˙ O2 responses were very similar between the ELD and YG, and being independent of the periods of sinusoidal oscillations. In marked contrast, the PS of the HR kinetics was significantly slowed in the ELD compared to the YG. The Amp ratio of HR was not related to the covariance variation of HR (CVHR) at standing rest in the ELD. The HR kinetics during sinusoidal walking may not be attributable to parasympathetic nerve activity into the heart in the ELD. The slope of the Amp of V˙E related to the Amp of V˙ CO2 ( V˙E/ V˙ CO2 slope) was steeper in the ELD (0.0258) compared to the YG (0.0132), suggesting that exercise hyperpnea could be greatly induced during walking in the ELD. These findings suggest that aging influences the alterations of autonomic nervous system-dependent slower HR kinetics and exercise hyperpnea during walking in the ELD.

Effect of electroacupuncture stimulation on long-term recovery following Achilles tendon rupture in a rat model.

AIMS: In this study we examined the effect of electroacupuncture (EA) stimulation on the mechanical strength of the rat Achilles tendon after long-term recovery. METHODS: Using 20 rats, an Achilles tendon rupture model was created in an invasive manner. The rats were assigned to one of three groups, that received EA treatment (EA group), minimal acupuncture (MA group) or remained untreated (Control group). In the EA group, EA stimulation (5 ms, 50 Hz, 20 µA, 20 min) was applied to the rupture region over a period of 90 days (five times/week). In the MA group, needles were inserted into the same positions as in the EA group but no electrical current was applied. After 90 days the tendon was measured to calculate the cross-sectional area of the rupture region. Then, the mechanical strength of the tendon was measured by tensile testing. RESULTS: No significant differences were observed between the three groups in cross-sectional area of the injured tendon. For maximum breaking strength, the EA group showed a significantly higher threshold compared with the Control group (P<0.05) but not the MA group (P=0.24). No significant difference was seen between the MA group and the Control group (P=0.96). CONCLUSION: Given the EA group showed a significant increase in maximum breaking strength, it is likely that EA stimulation increases the mechanical strength of a repaired tendon after long-term recovery, and EA stimulation could be useful for preventing re-rupture.