Acute Effects of Various Stretching Techniques on Range of Motion: A Systematic Review with Meta-Analysis

Background

Although stretching can acutely increase joint range of motion (ROM), there are a variety of factors which could influence the extent of stretch-induced flexibility such as participant characteristics, stretching intensities, durations, type (technique), and muscle or joint tested.

Objective

The objective of this systematic review and meta-analysis was to investigate the acute effects of stretching on ROM including moderating variables such as muscles tested, stretch techniques, intensity, sex, and trained state.

Methods

A random-effect meta-analysis was performed from 47 eligible studies (110 effect sizes). A mixed-effect meta-analysis subgroup analysis was also performed on the moderating variables. A meta-regression was also performed between age and stretch duration. GRADE analysis was used to assess the quality of evidence obtained from this meta-analysis.

Results

The meta-analysis revealed a small ROM standard mean difference in favor of an acute bout of stretching compared to non-active control condition (ES = −0.555; Z = −8.939; CI (95%) −0.677 to −0.434; p  < 0.001; I2 = 33.32). While there were ROM increases with sit and reach (P  = 0.038), hamstrings (P  < 0.001), and triceps surae (P  = 0.002) tests, there was no change with the hip adductor test (P  = 0.403). Further subgroup analyses revealed no significant difference in stretch intensity (P  = 0.76), trained state (P  = 0.99), stretching techniques (P  = 0.72), and sex (P  = 0.89). Finally, meta-regression showed no relationship between the ROM standard mean differences to age (R2 = −0.03; P  = 0.56) and stretch duration (R 2 = 0.00; P  = 0.39), respectively. GRADE analysis indicated that we can be moderately confident in the effect estimates.

Conclusion

A single bout of stretching can be considered effective for providing acute small magnitude ROM improvements for most ROM tests, which are not significantly affected by stretch intensity, participants’ trained state, stretching techniques, and sex.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-023-00652-x.

The meta-analysis on joint range of motion (ROM) increases revealed a small effect size in favor of an acute bout of stretching compared to the control condition. Subgroup analysis revealed a significant increase in ROM with sit and reach, hamstrings, and triceps surae tests, but no improvement with the hip adductor tests. Whereas all moderating variables presented significant increases in ROM, further subgroup analyses revealed no significant difference in ROM gains with the stretch intensity, trained state of the participants, stretching techniques, and sex. A meta-regression showed no relationship between the effect sizes to age and stretch duration, respectively.

Corticospinal excitability and reflex modulation in a contralateral non-stretched muscle following unilateral stretching

PURPOSE

Muscle stretching effect on the range of motion (ROM) and force deficit in non-stretched muscle, and the underlying mechanisms, is an ongoing issue. This study aimed to investigate crossover stretching effects and mechanisms on the plantar flexor muscles.

METHODS

Fourteen recreationally active females (n = 5) and males (n = 9) performed six sets of 45-s static stretching (SS) (15-s recovery) to the point of discomfort of the dominant leg (DL) plantar flexors or control (345-s rest). Participants were tested for a single 5-s pre- and post-test maximal voluntary isometric contraction (MVIC) with each plantar flexor muscle and were tested for DL and non-DL ROM. They were tested pre- and post-test (immediate, 10-s, 30-s) for the Hoffman (H)-reflex and motor-evoked potentials (MEP) from transcranial magnetic stimulation in the contralateral, non-stretched muscle.

RESULTS

Both the DL and non-DL-MVIC force had large magnitude, significant (↓10.87%, p = 0.027, pƞ2 = 0.4) and non-significant (↓9.53%, p = 0.15, pƞ2 = 0.19) decreases respectively with SS. The SS also significantly improved the DL (6.5%, p < 0.001) and non-DL (5.35%, p = 0.002) ROM. The non-DL MEP/MMax and HMax/MMax ratio did not change significantly.

CONCLUSION

Prolonged static stretching improved the stretched muscle's ROM. However, the stretched limb's force was negatively affected following the stretching protocol. The ROM improvement and large magnitude force impairment (statistically non-significant) were transferred to the contralateral muscles. The lack of significant changes in spinal and corticospinal excitability confirms that the afferent excitability of the spinal motoneurons and corticospinal excitability may not play a substantial role in non-local muscle's ROM or force output responses.

Purification of Plasmodium and Babesia- infected erythrocytes using a non-woven fabric filter

The purification of parasite-infected erythrocytes from whole blood containing leucocytes is crucial for many downstream genetic and molecular assays in parasitology. Current methodologies to achieve this are often costly and time consuming. Here, we demonstrate the successful application of a cheap and simple Non-Woven Fabric (NWF) filter for the purification of parasitized red blood cells from whole blood. NWF filtration was applied to the malaria-parasitized blood of three strains of mice, and one strain of rat, and to Babesia gibsoni parasitized dog blood. Before and after filtration, the white blood cell (WBC) removal rates and red blood cell (RBC) recovery rates were measured. After NWF filter treatment of rodent malaria-infected blood, the WBC removal rates and RBC recovery rates were, for Kunming mice: 99.51%±0.30% and 86.12%±8.37%; for BALB/C mice: 99.61%±0.15% and 80.74%±7.11%; for C57 mice: 99.71%±0.12% and 84.87%±3.83%; for Sprague-Dawley rats: 99.93%±0.03% and 83.30%±2.96%. Microscopy showed WBCs were efficiently removed from infected dog blood samples, and there was no obvious morphological change of B. gibsoni parasites. NWF filters efficiently remove leukocytes from malaria parasite-infected mouse and rat blood, and are also suitable for filtration of B. gibsoni-infected dog blood.

Antimalarial drugs clear resistant parasites from partially immune hosts

Circumstantial evidence in human malaria suggests that elimination of parasites by drug treatment meets higher success rates in individuals having some background immunity. In this study, using the rodent malaria model Plasmodium chabaudi, we show that drug-resistant parasites can be cleared by drugs when the host is partially immune.