Ishizaki T1, Sugiura S1,2, Toyooka T1, Ooyama T1, Kote A1, Watanabe J1, Takeda T1, Shinozaki M1, Okamoto Y3, Nishikawa S3
1Nishikawa Orthopaedic Clinic, Rehabiltation, Sakura, Japan, 2Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan, 3Nishikawa Orthopaedic Clinic, Sakura, Japan
Background: Tight hamstrings are reported to be one of the causes of low back pain. It has also been reported that jack-knife stretching is useful for treating tight hamstrings. However, there has been no report of the effect of jack-knife stretching on muscle power output and spinal alignment in the sagittal plane.
Purpose: The purpose of this study is to compare the immediate effects of jack-knife stretching on hamstring flexibility, quadriceps muscle power output and spinal alignment.
Methods: A total of 12 healthy adults (mean age: 30.1 ±5.85 years-old; male:7; female:5) were recruited for this study. Exclusion criteria included a history of lumbar spine disorder, neurological disorder, or spinal surgery. In the jack-knife stretch subjects began in a squat-down position with feet shoulder-width apart and hands holding their ankles. While still holding their ankles, subjects rose up by extending their knees, keeping their upper core bent forward and their chest in as much contact as possible with their thighs, holding the hamstring stretch for 10 seconds. Subjects repeated the jack-knife stretching five times. Before and immediately after jack-knife stretching, finger-floor distance (FFD), weight-bearing index (WBI: quadriceps isometric muscle strength/body weight) and sagittal spinal alignment were assessed. WBI was measured using the isoforce GT-360 (OG Wellness CO, Ltd. Japan). For sagittal spinal alignment, lumbar lordosis angle (LLA), sacral anterior inclination angle (SAIA), and thoracic kyphosis angle (TKA) while standing were measured using a Spinal Mouse (Index CO, Ltd. Swiss). The results were statistically compared using the Wilcoxon Signed-Rank test between before and immediately after jack-knife stretching (within 5 minutes from the finishing stretch). A p value 0.05 was considered statistically significant. Values are expressed as mean ± standard deviation (SD).
Results: FFD was -0.4±10.3 cm before, decreasing to -4.5±8.8 cm after jack-knife stretching (p 0.01), indicating a gain in flexibility of 4.1 cm. WBI was 1.07±0.33 before, increasing to 1.15±0.31 after jack-knife stretching (p 0.05). Before and after jack-knife stretching, LLA was 19.0±6.1° and 21.0±5.9° and SAIS was 10.9±5.5° and 12.5±5.7° respectively; these differences were significant (p 0.05). Before and after jack-knife stretching, TKA was 35.2±8.0° and 35.7±7.8°; this difference was not significant.
Conclusion(s): Jack-knife stretching has been reported to improve flexibility in FFD after a 4-week stretching program. The results of this study indicate that jack-knife stretching has an immediate positive effect on hamstring flexibility. In addition, muscle power output and lumbar lordosis and pelvic alignment were also improved.
Implications: These results suggest that jack-knife stretching would be useful for immediate improvement of tight hamstrings, muscle power output and sagittal lumbar-pelvic alignment.
Keywords: JACK-KNIFE STRETCHING, MUSCLE POWER OUTPUT, SPINAL ALIGNMENT
Funding acknowledgements: This research did not receive any specific grant from agencles in the public,commercial,or not-for-profit sectors.
Purpose: The purpose of this study is to compare the immediate effects of jack-knife stretching on hamstring flexibility, quadriceps muscle power output and spinal alignment.
Methods: A total of 12 healthy adults (mean age: 30.1 ±5.85 years-old; male:7; female:5) were recruited for this study. Exclusion criteria included a history of lumbar spine disorder, neurological disorder, or spinal surgery. In the jack-knife stretch subjects began in a squat-down position with feet shoulder-width apart and hands holding their ankles. While still holding their ankles, subjects rose up by extending their knees, keeping their upper core bent forward and their chest in as much contact as possible with their thighs, holding the hamstring stretch for 10 seconds. Subjects repeated the jack-knife stretching five times. Before and immediately after jack-knife stretching, finger-floor distance (FFD), weight-bearing index (WBI: quadriceps isometric muscle strength/body weight) and sagittal spinal alignment were assessed. WBI was measured using the isoforce GT-360 (OG Wellness CO, Ltd. Japan). For sagittal spinal alignment, lumbar lordosis angle (LLA), sacral anterior inclination angle (SAIA), and thoracic kyphosis angle (TKA) while standing were measured using a Spinal Mouse (Index CO, Ltd. Swiss). The results were statistically compared using the Wilcoxon Signed-Rank test between before and immediately after jack-knife stretching (within 5 minutes from the finishing stretch). A p value 0.05 was considered statistically significant. Values are expressed as mean ± standard deviation (SD).
Results: FFD was -0.4±10.3 cm before, decreasing to -4.5±8.8 cm after jack-knife stretching (p 0.01), indicating a gain in flexibility of 4.1 cm. WBI was 1.07±0.33 before, increasing to 1.15±0.31 after jack-knife stretching (p 0.05). Before and after jack-knife stretching, LLA was 19.0±6.1° and 21.0±5.9° and SAIS was 10.9±5.5° and 12.5±5.7° respectively; these differences were significant (p 0.05). Before and after jack-knife stretching, TKA was 35.2±8.0° and 35.7±7.8°; this difference was not significant.
Conclusion(s): Jack-knife stretching has been reported to improve flexibility in FFD after a 4-week stretching program. The results of this study indicate that jack-knife stretching has an immediate positive effect on hamstring flexibility. In addition, muscle power output and lumbar lordosis and pelvic alignment were also improved.
Implications: These results suggest that jack-knife stretching would be useful for immediate improvement of tight hamstrings, muscle power output and sagittal lumbar-pelvic alignment.
Keywords: JACK-KNIFE STRETCHING, MUSCLE POWER OUTPUT, SPINAL ALIGNMENT
Funding acknowledgements: This research did not receive any specific grant from agencles in the public,commercial,or not-for-profit sectors.
Topic: Sport & sports injuries; Sport & sports injuries; Education: clinical
Ethics approval required: Yes
Institution: Nishikawa Orthopedic Clinic
Ethics committee: Ethical Review Committee of Nishikawa Orthopaedic Clinic
Ethics number: 2426
All authors, affiliations and abstracts have been published as submitted.
