The Relationship between Stretching Intensity and Changes in Passive Properties of Gastrocnemius Muscle-Tendon Unit after Static Stretching

The Effects of 5 Minutes of Static Stretching on Joint Flexibility and Muscle Strength Are Comparable Between Ballet Dancers and Non-Dancers

Introduction: Ballet dancers have a special morphology, such as a large muscle thickness that affects passive torque. Ballet dancers also possess specialized mechanical, and neural properties of muscles and tendons. These characteristics may produce different static stretching effects than non-dancers. Therefore, this study aimed to determine the differences in the effects of static stretching on joint range of motion, passive torque, and muscle strength between ballet dancers and non-dancers. Methods: This study included 13 ballet dancers and 13 college students. The muscle and tendon thicknesses were assessed using ultrasonography. In the right lower extremity, torque-angle data and muscle-tendon junction displacement measurements were obtained during isokinetic passive dorsiflexion before and after a 5-minute static stretch against the right plantar flexors. The relative stretching intensity was calculated by dividing the stretching angle by the maximal dorsiflexion angle pre-stretch. Additionally, the isometric maximal voluntary plantar flexion torque on the left ankle was measured before and after 5 minutes of static stretching against the left plantar flexors. Results: Ballet dancers had significantly greater muscle thickness than non-dancers (22.4 ± 2.2 vs 18.1 ± 1.7 mm), whereas no significant difference was observed in the Achilles tendon thickness. No significant difference was observed in the stretching angle; however, the relative stretching intensity was higher in the control group (65.9 ± 19.8 vs 127.5 ± 63.8%). Static stretching increased the maximal dorsiflexion angle (dancer: 30.4° ± 9.6° to 33.9° ± 9.5°, non-dancer: 18.4° ± 8.6° to 20.5° ± 9.5°) and maximal passive torque in both groups, whereas the maximal isometric plantar flexion torque and submaximal passive torque decreased. However, no significant differences were observed in the changes between the groups. Conclusion: These results indicate that despite having a lower relative stretching intensity, ballet dancers experienced similar changes as non-dancers after 5 minutes of static stretching.

The Acute Effect of Percussive Massage Intervention with and without Heat Application on Plantar Flexor Muscles' Passive and Active Properties

Recently, percussive massage (PM) intervention using a handheld percussive massage device, namely a massage gun, has been used as an easy way to perform vibration functions. Additionally, a product has been developed that allows PM intervention and heat application to be performed simultaneously. Thus, this study aimed to compare the acute effects of PM intervention with and without heat application on dorsiflexion (DF) range of motion (ROM), passive stiffness, and muscle strength in the gastrocnemius muscle. Fifteen healthy young men (20.9 ± 0.2 years) participated in this study. We measured the DF ROM, passive torque at DF ROM (an indicator of stretch tolerance), passive stiffness, and maximum voluntary isometric contraction (MVIC) torque of the plantar flexor muscles before and immediately after 120 seconds PM intervention with and without heat application. The results showed that PM intervention with and without heat application significantly increased DF ROM and passive torque at DF ROM and decreased passive stiffness, not MVIC torque. These results suggest that PM intervention increased ROM and decreased passive stiffness regardless of the presence or absence of the heat application.

Acute effects of resistance training at different range of motions on plantar flexion mechanical properties and force

The effects obtained from resistance training depend on the exercise range of motion (ROM) performed. We aimed to examine the acute effects of different exercise ROM resistance training on the plantar flexor muscles. Eighteen healthy untrained male adults participated in three conditions: calf raises in 1) partial condition [final (short muscle length) partial ROM], 2) full condition (full ROM), and 3) control condition. The ankle dorsiflexion (DF) ROM, passive torque at DF ROM, passive stiffness of muscle-tendon unit, and maximal voluntary isometric contraction (MVC-ISO) torque were measured before and immediately after the interventions. There were significant increases in DF ROM, passive torque at DF ROM, and a decrease in MVC-ISO, but no significant interaction in passive stiffness. Post hoc test, DF ROM demonstrated moderate magnitude increases in the full condition compared to the partial (p = 0.023, d = 0.74) and control (p = 0.003, d = 0.71) conditions. Passive torque at DF ROM also showed moderate magnitude increases in the full condition compared to the control condition (p = 0.016, d = 0.69). MVC-ISO had a moderate magnitude decrease in the full condition compared to the control condition (p = 0.018, d=-0.53). Resistance training in the full ROM acutely increases joint ROM to a greater extent than final partial ROM, most likely due to stretch tolerance.

Combined Static Stretching and Electrical Muscle Stimulation Induce Greater Changes in Range of Motion, Passive Torque, and Tendon Displacement Compared with Static Stretching

The purpose of this study was to determine the combined effects of static stretching and electrical muscle stimulation on maximal dorsiflexion angle and passive properties. Sixteen healthy subjects participated in three randomly ordered experimental trials: combined static stretching and electrical muscle stimulation, static stretching alone, and control. In combined trial, subjects performed 5 min of calf stretching while receiving electrical muscle stimulation of the gastrocnemius medialis. In static stretching trial, subjects performed calf stretching only. Maximal dorsiflexion angle, passive torque, and muscle displacement were measured before and after intervention. Tendon displacement was also calculated. The difference from pre- to post-intervention in maximal dorsiflexion angle in combined trial was greater compared with that in the control (p = 0.026), but the static stretching trial exhibited no significant difference (both p > 0.05). Passive torque at submaximal dorsiflexion angles was significantly decreased only after combined trial (all p < 0.05). Muscle displacement at maximal dorsiflexion angle was significantly increased in all conditions (all p < 0.05). Tendon displacement at maximal dorsiflexion angle was higher after combined trial compared with static stretching trial (p = 0.030). These results revealed additional effects of adding electrical muscle stimulation to static stretching on maximal dorsiflexion angle, passive torque, and tendon displacement.

Local and Non-local Effects of Foam Rolling on Passive Soft Tissue Properties and Spinal Excitability

In sports and clinical settings, roller massage (RM) interventions are used to acutely increase range of motion (ROM); however, the underlying mechanisms are unclear. Apart from changes in soft tissue properties (i.e., reduced passive stiffness), neurophysiological alterations such as decreased spinal excitability have been described. However, to date, no study has investigated both jointly. The purpose of this trial was to examine RM’s effects on neurophysiological markers and passive tissue properties of the plantar flexors in the treated (ROLL) and non-treated (NO-ROLL) leg. Fifteen healthy individuals (23 ± 3 years, eight females) performed three unilateral 60-s bouts of calf RM. This procedure was repeated four times on separate days to allow independent assessments of the following outcomes without reciprocal interactions: dorsiflexion ROM, passive torque during passive dorsiflexion, shear elastic modulus of the medial gastrocnemius muscle, and spinal excitability. Following RM, dorsiflexion ROM increased in both ROLL (+19.7%) and NO-ROLL (+13.9%). Similarly, also passive torque at dorsiflexion ROM increased in ROLL (+15.0%) and NO-ROLL (+15.2%). However, there were no significant changes in shear elastic modulus and spinal excitability (p > 0.05). Moreover, significant correlations were observed between the changes in DF ROM and passive torque at DF ROM in both ROLL and NO-ROLL. Changes in ROM after RM appear to be the result of sensory changes (e.g., passive torque at DF ROM), affecting both rolled and non-rolled body regions. Thus, therapists and exercise professionals may consider applying remote treatments if local loading is contraindicated.

Training and Detraining Effects Following a Static Stretching Program on Medial Gastrocnemius Passive Properties

A stretching intervention program is performed to maintain and improve range of motion (ROM) in sports and rehabilitation settings. However, there is no consensus on the effects of stretching programs on muscle stiffness, likely due to short stretching durations used in each session. Therefore, a longer stretching exercise session may be required to decrease muscle stiffness in the long-term. Moreover, until now, the retention effect (detraining) of such an intervention program is not clear yet. The purpose of this study was to investigate the training (5-week) and detraining effects (5-week) of a high-volume stretching intervention on ankle dorsiflexion ROM (DF ROM) and medial gastrocnemius muscle stiffness. Fifteen males participated in this study and the plantarflexors of the dominant limb were evaluated. Static stretching intervention was performed using a stretching board for 1,800 s at 2 days per week for 5 weeks. DF ROM was assessed, and muscle stiffness was calculated from passive torque and muscle elongation during passive dorsiflexion test. The results showed significant changes in DF ROM and muscle stiffness after the stretching intervention program, but the values returned to baseline after the detraining period. Our results indicate that high-volume stretching intervention (3,600 s per week) may be beneficial for DF ROM and muscle stiffness, but the training effects are dismissed after a detraining period with the same duration of the intervention.