Influence of One Hour versus Two Hours of Daily Static Stretching for Six Weeks Using a Calf-Muscle-Stretching Orthosis on Maximal Strength

Abstract

Rebuilding strength capacity is of crucial importance in rehabilitation since significant atrophy due to immobilization after injury and/or surgery can be assumed. To increase maximal strength (MSt), strength training is commonly used. The literature regarding animal studies show that long-lasting static stretching (LStr) interventions can also produce significant improvements in MSt with a dose–response relationship, with stretching times ranging from 30 min to 24 h per day; however, there is limited evidence in human studies. Consequently, the aim of this study is to investigate the dose–response relationship of long-lasting static stretching on MSt. A total of 70 active participants (f = 30, m = 39; age: 27.4 ± 4.4 years; height: 175.8 ± 2.1 cm; and weight: 79.5 ± 5.9 kg) were divided into three groups: IG1 and IG2 both performed unilateral stretching continuously for one (IG1) or two hours (IG2), respectively, per day for six weeks, while the CG served as the non-intervened control. MSt was determined in the plantar flexors in the intervened as well as in the non-intervened control leg to investigate the contralateral force transfer. Two-way ANOVA showed significant interaction effects for MSt in the intervened leg (ƞ 2 = 0.325, p < 0.001) and in the contralateral control leg (ƞ 2 = 0.123, p = 0.009), dependent upon stretching time. From this, it can be hypothesized that stretching duration had an influence on MSt increases, but both durations were sufficient to induce significant enhancements in MSt. Thus, possible applications in rehabilitation can be assumed, e.g., if no strength training can be performed, atrophy could instead be reduced by performing long-lasting static stretch training.

Using Daily Stretching to Counteract Performance Decreases as a Result of Reduced Physical Activity—A Controlled Trial

“…The maximum isometric strength in a 90° knee joint angle (MVC90) was recorded for both legs using bilateral maximum strength testing. The measurement procedure was performed as previously described in Warneke et al [ 27 ]. For this purpose, the subject was instructed to perform plantar flexion for three seconds with the maximum possible force in response to an acoustic signal to press against the pad of the measuring device.…”

“…A charge amplifier, “Typ5009 Charge Amplifier”, and a 13-bit analog-to-digital converter NI6009 were used. The reliability can be classified as high with ICC = 0.994 [ 27 ].…”

“…However, there are limited possibilities for using heavy weights in a home-based training program during a period of inactivity or immediately after injury; therefore, alternative training methods are required to counteract MSt impairments. Fortunately, current literature points out the use of high-volume stretch training to improve MSt (29%; d = 1.24), muscle thickness (MTh) (15.3%; d = 0.84) and range of motion (ROM) (27.3%; d = 0.87) using two to seven sessions per week with stretching durations of up to two hours per day for six to ten weeks [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. In contrast to the highly effective improvements in MSt, MTh and ROM when using two hours of daily stretching, Yahata et al [ 23 ] were also able to show significant (6% (d = 0.35)) increases in plantar flexor MSt using stretching for durations of only 30 min (6 × 5 min) two days per week using a stretching board.…”

Using Long-Duration Static Stretch Training to Counteract Strength and Flexibility Deficits in Moderately Trained Participants

“…The leg press sled was fixed in position with industrial-grade tensioning straps so that the starting position was set to an ankle joint angle of 90° with the metatarsophalangeal joint of the foot placed on the edge flush (see Figure 2 a). The testing procedure and devices were validated and described in [ 30 , 31 ]. Subjects performed an isometric MVC against the force plate in response to an acoustic signal and held the contraction for three seconds.…”

“…However, considering the assumption that, especially directly after surgery, a strength training must not be performed, it seems beneficial to resort to alternative training routines to accelerate the rehabilitation process. Results from animal studies provide evidence that long-duration stretch training also leads to significant increases in MSt, MTh and muscle length [ 29 ] with an assumed transferability to humans [ 30 , 31 ]. As static stretching does not require active (joint) movement (i.e., reduced activation of the central nervous system) and can be included in seated activities, it can be performed with a high frequency (i.e., daily).…”