eccentric hamstring muscle strength and muscle activity of the biceps femoris during the late swing phase showed a strong positive association with the ability to produce horizontal ground reaction force during the sprint acceleration phase. 8 In line with this, strength training interventions focusing on
Lasse Ishøi, Per Aagaard, Mathias F. Nielsen, Kasper B. Thornton, Kasper K. Krommes, Per Hölmich and Kristian Thorborg
José M. Muyor, Pedro A. López-Miñarro and Fernando Alacid
The aim was to determine the relationship between hamstring muscle extensibility and sagittal spinal curvatures and pelvic tilt in cyclists while adopting several postures. A total of 75 male cyclists were recruited for this study (34.79 ± 9.46 years). Thoracic and lumbar spine and pelvic tilt were randomly measured using a Spinal Mouse. Hamstring muscle extensibility was determined in both legs by a passive knee extension test. Low relationships were found between hamstring muscle extensibility and spinal parameters (thoracic and lumbar curvature, and pelvic tilt) in standing, slumped sitting, and on the bicycle (r = .19; P > .05). Significant but low relationships were found in maximal trunk flexion with knees flexed (r = .29; P < .05). In addition, in the sit-and-reach test, low and statistically significant relationships were found between hamstring muscle extensibility for thoracic spine (r = –.23; P = .01) and (r = .37; P = .001) for pelvic tilt. In conclusion, hamstring muscle extensibility has a significant relationship in maximal trunk flexion postures with knees flexed and extended, but there are no relationships while standing or on the bicycle postures.
J. Allen Hardin, John A. Guido and Christopher J. Hughes
Due to the likelihood of hamstring dysfunction associated with anterior cruciate ligament (ACL) injury, it is clinically significant to determine if a hamstring weakness exists preoperatively. The purpose of this study was to determine if a hamstring muscle deficit existed at the time of surgery and to determine the time necessary to achieve hamstring strength equal to preoperative measures of the uninvolved extremity during postoperative rehabilitation. Twelve patients who underwent ACL reconstruction using a patellar tendon autograft participated. Each subject underwent a preoperative isometric knee strength evaluation at 60° of knee flexion. Each subject underwent postoperative rehabilitation including hamstring muscle strengthening. Repeat isometric testing was performed on each subject at 21 and 42 days postoperative. There was no statistical difference in hamstring muscle strength, as measured by isometric peak torque, either preoperatively or postoperatively. Therefore, maintaining rather than increasing hamstring strength postoperatively should be emphasized as an integral part of rehabilitation.
Teddy W. Worrell, Michael K. Sullivan and Joseph J. DeJulia
This study examined the intratester and intertester reliability of an active-knee-extension test (AKET) for determining hamstring muscle length (flexibility). Three testers performed repeated AKET measurements on 22 subjects. Intraclass correlation coefficients (ICC were used to calculate intratester and intertester reliability. Also, standard error of measurements (SEM) were calculated. The ICC and SEM were .96 and 1.82°, respectively, for Tester 1, .99 and 1.75° for Tester 2, and .99 and 1.80° for Tester 3. Intratester 95% confidence intervals ranged from 60.54 to 69.82°. Intertester ICC and SEM for two testers were .93 and 4.81°, respectively. A 95% intertester confidence interval ranged from 56.35 to 75.21 °; this reveals that intertester AKET values contained more error and suggests that only intratester AKET values should be used when comparing hamstring flexibility values. The AKET may provide a more accurate method for determining hamstring flexibility and quantifying changes that occur as a result of injury and stretching procedures.
Paul W.M. Marshall, Ric Lovell and Jason C. Siegler
Passive muscle tension is increased after damaging eccentric exercise. Hamstring-strain injury is associated with damaging eccentric muscle actions, but no research has examined changes in hamstring passive muscle tension throughout a simulated sport activity. The authors measured hamstring passive tension throughout a 90-min simulated soccer match (SAFT90), including the warm-up period and every 15 min throughout the 90-min simulation.
Passive hamstring tension of 15 amateur male soccer players was measured using the instrumented straight-leg-raise test. Absolute torque (Nm) and slope (Nm/°) of the recorded torque-angular position curve were used for data analysis, in addition to total leg range of motion (ROM). Players performed a 15-min prematch warm-up, then performed the SAFT90 including a 15-min halftime rest period.
Reductions in passive stiffness of 20–50° of passive hip flexion of 22.1−29.2% (P < .05) were observed after the warm-up period. During the SAFT90, passive tension increased in the latter 20% of the range of motion of 10.1−10.9% (P < .05) concomitant to a 4.5% increase in total hamstring ROM (P = .0009).
The findings of this study imply that hamstring passive tension is reduced after an active warm-up that includes dynamic stretching but does not increase in a pattern suggestive of eccentric induced muscle damage during soccer-specific intermittent exercise. Hamstring ROM and passive tension increases are best explained by improved stretch tolerance.
Che-Hsiu Chen, Trevor C. Chen, Mei-Hwa Jan and Jiu-Jenq Lin
To examine whether an acute bout of active or dynamic hamstring-stretching exercises would reduce the amount of muscle damage observed after a strenuous eccentric task and to determine whether the stretching protocols elicit similar responses.
A randomized controlled clinical trial.
Thirty-six young male students performed 5 min of jogging as a warm-up and were allocated to 1 of 3 groups: 3 min of static active stretching (SAS), 3 min of dynamic active stretching (DAS), or control (CON). All subjects performed eccentric exercise immediately after stretching. Heart rate, core temperature, maximal voluntary isometric contraction, passive hip flexion, passive hamstring stiffness (PHS), plasma creatine kinase activity, and myoglobin were recorded at prestretching, at poststretching, and every day after the eccentric exercises for 5 d.
After stretching, the change in hip flexion was significantly higher in the SAS (5°) and DAS (10.8°) groups than in the CON (–4.1°) group. The change in PHS was significantly higher in the DAS (5.6%) group than in the CON (–5.7%) and SAS (–6.7%) groups. Furthermore, changes in muscle-damage markers were smaller in the SAS group than in the DAS and CON groups.
Prior active stretching could be useful for attenuating the symptoms of muscle damage after eccentric exercise. SAS is recommended over DAS as a stretching protocol in terms of strength, hamstring range of motion, and damage markers.
Kohei Watanabe, Motoki Kouzaki and Toshio Moritani
In some muscles, nonuniform surface electromyography (EMG) responses have been demonstrated within a muscle, meaning that the electrode location could be critical in the results of surface EMG. The current study investigated possible region-specific EMG responses within the human biceps femoris (BF) muscle. Surface EMG was recorded from various regions along the longitudinal axis of the BF muscle with 20 electrodes. Ten healthy men performed maximal isometric contractions of hip extension and knee flexion, which involve the BF muscle. The ratio of the EMG amplitude between hip extension and knee flexion tasks (HE/KF) was calculated and compared among the regions. There were no significant differences in HE/KF among the regions along the BF muscle (P > .05). This suggests that the entire superficial region of the BF muscle is equally regulated in the 2 different tasks. We suggest that the electrode location is not critical in estimating the activation properties and/or functional role of the superficial region, which corresponds with approximately 50% of the muscle length of the BF muscle, using surface EMG during maximal contraction.
Özlem Aslan, Elif Balevi Batur and Jale Meray
forces of hamstring and quadriceps muscles with functional H/Q ratio, weakness was determined in both quadriceps and hamstring muscles. However, in most studies, the function of the knee joint and thigh muscles is conventionally defined using many techniques. The ratio of maximum isokinetic hamstring
Noureddin Nakhostin Ansari, Parisa Alaei, Soofia Naghdi, Zahra Fakhari, Shiva Komesh and Jan Dommerholt
Flexibility has been defined as the muscle extensibility reflected in the amount of joint range of motion (ROM). 1 The maximal muscle length that contributes to the maximal ROM of a joint is essential for activities of daily living and sports performances. Flexibility of the hamstring muscle plays
Jeffrey G. Williams, Hannah I. Gard, Jeana M. Gregory, Amy Gibson and Jennifer Austin
In college soccer, 53% of injuries are muscular in nature. 1 Of all muscular injuries, 47% of strains involve the hamstring muscle group, 2 making hamstring injuries the most common injuries among soccer players. 1 , 3 Such findings of hamstring injury among this population are likely due to the