Comparison of EMG activity of medial and lateral hamstrings during isometric contractions at various cuff weight loads.

Since both the medial head (MH) and lateral head (LH) of the hamstring muscles contribute to knee flexion, this study investigated whether the relative electrical activity of these heads remained constant with respect to each other or changed during isometric contractions at five different resistance levels. The relative electrical activity of these two heads was determined by comparing their integrated EMG (iEMG). Forty-two volunteers with no history of right lower extremity injury or disease, between the ages of 18 and 35, were studied. Following motor point location, surface electrodes were placed over the MH and LH. Subjects, positioned prone, flexed the knee to 45 degrees using a sawhorse as a tactile cue to help maintain this position. Three recordings, 8 s in length, were taken at each subject's maximum isometric contraction and then using cuff weights of 1, 3, 5, and 7% of their body weight. The average of the three recordings was used in the analysis. During maximum isometric contraction (at 45 degrees of knee flexion), the LH contributes a significantly greater percent of the total iEMG (63.4%) than the MH (P < 0.0001). Furthermore, within the four submaximal levels tested, the LH's contribution was significantly greater than the MH (P < 0.01). During submaximal isometric contractions, the LH percent contribution to total iEMG was less than its contribution during maximal isometric contraction, all P values < 0.005. As a result, during these same submaximal isometric contractions, the MH contribution to total iEMG was greater than its contribution during maximal isometric contraction, all P values < 0.005).

Integrated EMG study of the medial and lateral heads of the gastrocnemius during isometric plantar flexion with varying cuff weight loads.

Both heads of the gastrocnemius muscle contribute to ankle plantar flexion. This study utilized integrated electromyography to investigate whether the percent electrical activity contributed by each head remained constant or changed during isometric contractions at five different resistance levels. Fifty healthy volunteers ranging in age from 19 to 34 years, with no history of musculoskeletal or neuromuscular disorders involving the right lower extremity, were studied. All tasks were performed in the prone position, knee in extension, with the leg and foot in neutral with respect to rotation. Motor points of the medial head and lateral head were identified and surface electrodes were placed just distal to them. The subjects maintained 20° of plantar flexion under five conditions: a maximal isometric plantar flexion contraction (one trial only), and with a 5-, 10-, 15- and 20-lb cuff weight attached to the right foot (three trials each). EMG recordings, 8 s in length, were taken during the isometric contractions. Integrated EMGs were averaged for each cuff weight and the resulting values used in the analysis. A repeated measures ANOVA was performed and a significance level of p≤0.05 was used to determine statistical significance. As weight increased, the absolute value of the integrated EMG recorded over both muscles increased, but the percent contributed by each head remained essentially equal (50%) within the four submaximal loads tested. However, for the maximal isometric contraction, the medial head contributed a significantly higher percentage of the total integrated EMG (58%). Therefore, in the open-chain activity described, the two heads of the gastrocnemius demonstrate similar neural drive at submaximal levels of contraction, but this changes as maximum isometric levels are reached.

EMG activity of medial and lateral hamstrings at three positions of tibial rotation during low-force isometric knee flexion contractions.

The purpose of this investigation was to determine how the position of tibial rotation effects the EMG activity of the medial and lateral hamstrings during low-force isometric knee flexion contractions. Forty-five subjects (ages 18-35) with no history of lower extremity injury or disease volunteered for this study. While lying prone, and with surface EMG electrodes secured to the bellies of their right medial (semitendinous and semimembranosus) and lateral (long head of the biceps femoris) hamstring muscles, each subject held the knee in 45° of flexion for 8 s against 5% of their body weight. This was performed three times in each of the positions of neutral tibial rotation, external tibial rotation, and internal tibial rotation. The root-mean-square (RMS) of the EMG activity from these muscles was determined for each of the contractions. A repeated measures ANOVA was used to compare the RMS values of the two muscle groups in the three positions. The average RMS values (in microvolts [mV]) obtained were (means and standard deviation): medial hamstrings in external rotation: 50.74 ± 23.11; in neutral: 65.57 ± 25.35; in internal rotation: 70.73 ± 31.86; lateral hamstrings in external rotation: 66.08 ± 46.99; in neutral: 46.18 ± 39.34; in internal rotation: 27.68 ± 17.86. A statistically significant interaction was found between tibial rotation and hamstring muscle (p < 0.0001). These results are consistent with the presumed function of these muscles in that EMG activity in the medial hamstrings increased when the tibia was rotated internally, whereas the lateral hamstring EMG activity increased when the tibia was rotated externally.

An overview of functional progressions in the rehabilitation of low back patients.

Low back pain is one of the most common dysfunctions seen by health care professionals. Eighty percent of the population will suffer from low back pain in their adult life.1-4 Accordingly, this societal problem has taken its toll via missed days of work and the adverse economic impact that results.3-9The good news is that most people with low back pain improve within a short period of time.1,9-11 Acute attacks of back pain and sciatica can last up to two weeks with chronic attacks persisting for more than three months.10 Vukmir reported that 74.2% of patients with low back pain improved within one month, 87.3% within three months, and 92.6% within six months.1 Additional good news is the fact that surgery is the appropriate solution for only a small percentage of the patients with low back pain.12,13 Saal and Saal report that nonoperative treatment for lumbar disorders, including intervertebral disc dysfunction prove most successful.13 Weber, in a landmark study, reported that patients who received surgery for lumbar disc herniations showed statistically better results at the one-year follow-up examination. However, at the four-year follow-up, there were no statistically significant differences in how patients who received surgery compared to the patients who did not receive surgery.14On a less positive note, people who suffer an episode of low back pain, have a greater chance of developing future episodes.10,15 Those patients who develop repeated episodes of low back pain and those patients who do not improve spontaneously over a short period of time can fall into the group known as chronic low back pain. This group creates a major drain on our economic resources and leads to a large number of people who are deemed disabled.1,7,8,12 Therefore, if the health care community is unable to cure all types of low back pain, keeping patients with low back pain functional should be of prime importance. Through the performance of functional activities, such as activities of daily living and working, the societal drain caused by low back pain, would hopefully decrease.

Thoracic segmental flexion during cervical forward bending.

The purpose of this study was to assess the amount of thoracic segmental flexion associated with cervical forward bending. Twenty-four healthy men and women between the ages of 21-29, with no past or present cervical or thoracic dysfunction, participated. Spinal segmental mobility in the thoracic region was measured in the neutral sitting position and sitting with the cervical spine in the forward bent position. Mobility was measured by the Faro Metrecom Skeletal Analysis System. The Faro Metrecom is an external measuring device that records each individual spinal segment's position within the body. Descriptive statistics were used to describe the position of the thoracic segments when the cervical region was in the neutral and in the forward bent positions. Additionally, intrarater reliability, .83 and .76, and interrater, .72, were analyzed for the thoracic segments in the neutral position. The results show that with cervical flexion there was thoracic segmental flexion. Segments T1-4 demonstrated forward bending ranging from 2.88-4.42°. The greatest amount of flexion occurred at T2, 4.42 degrees, and T3, 4.19 degrees. Below T4 no pattern was noted. The results indicate that upper-thoracic segmental flexion occurs during cervical forward bending.During evaluation and treatment of patients with cervical dysfunction physical therapists routinely evaluate spinal segmental mobility. It is clear to clinicians that cervical segmental mobility is important to cervical range of motion. What it not clear is the role of thoracic segmental mobility in cervical range of motion. Physical therapists frequently evaluate and treat the thoracic region when patients have cervical dysfunction. Therefore, the purpose of this study was to assess the amount of thoracic segmental flexion associated with cervical forward bending.Since the early 1970s when the concept of joint mobilization was brought to American physical therapists, interest in spinal segmental motion has increased. Though interest in this area exists, there is a scarcity ofresearch documenting normal and abnormal spinal segmental mobility. Additionally, most of the studies on spinal segmental mobility have been conducted on cadavers or through radiographic methods.Lysell studied intersegmental movements of the cervical spine using autopsy specimens. Steel balls were placed in fixed points on each vertebrae and then a three-dimensional radiographic examination was used to measure movements of these points during cervical range of motion.1 Ball and Meijers studied cervical mobility using fresh cadaveric cervical spinal specimens. In this study steel pins were inserted into the cervical bodies and serial x-rays were taken.2 Panjabi, Dvorak, and Duranceau studied upper-cervical spine mobility using fresh cadaveric whole cervical spine specimens and steel balls. Their specimens were set into a quick-setting epoxy material to help align the centers of C2 and C7, thereby providing fixation.3 Yamamoto et al. studied three-dimensional movements of the lumbar spine and lumbosacral joint. They used fresh cadaveric whole lumbar spine specimens analyzing from L1 to the sacrum.4 Robert studied intervertebral motion of the whole spine. This was performed with cadavers as the segmental excursions were determined from a point at the inferior surface of the vertebrae to the tip of the spinous process.5Three separate noncadaveric studies were conducted by Penning,6 Felding7 and Moll and Wright.8 Penning studied normal movements of the cervical spine by superimposing two x-ray films representing the cervical spine in the end positions (i.e., flexion and extension). Fielding studied normal and abnormal motion of the cervical spine from C2 and C7 using cineroentgenography; roentgenograms were taken while the subjects were moving. Moll and Wright studied normal range of spinal mobility using live subjects with markers on the skin. When the subjects moved the separation of the skin markers was recorded.The above studies used procedures that are not convenient for use during clinical sessions. Additionally, the above studies did not evaluate thoracic mobility in relation to cervical motion.In the textbook, Common Vertebral joint Problems,9 Grieve presents a complete discussion of vertebral motion. This section is highly referenced as it pertains to segmental spinal mobility.9 White and Panjabi are the most frequently cited source on spinal segmental mobility.10,11 They reported flexion/extension degrees of motion for the thoracic segments. The ranges of the motion and the "representative angle" (most likely the mean angle) in degrees for each thoracic segment are T1-T5 2-5 (4); T6 2-7 (5); T7-T9 3-8 (6); T10 4-14 (9); and T11-T12 6-20 (12). However, they did not state how their estimated range and "representative angle" in degrees of segmental spinal mobility were measured.10,11 Valencia in the book Physical Therapy of the Cervical and Thoracic Spine states similar motion for the thoracic segments.12The upper-thoracic spine, T1-T6, has been related to the cervical region anatomically. The upper-thoracic facet joints are orientated like the cervical facet joints and have a similar pattern of movement.11,13 Additionally, the caudal attachment of many cervical muscles is in the thoracic region.13.

Vestibular stimulation to improve ambulation after a cerebral vascular accident.

A pilot study was undertaken to determine if vestibular stimulation could be a valuable therapeutic measure in rehabilitating the patient who has had a cerebral vascular accident. Twenty patients with cerebral vascular accidents were tested. Changes in functional ambulation abilities of 10 patients receiving a passive vestibular exercise were compared with those of 10 patients not receiving this exercise. The vestibular stimulation was provided through a rotary stimulus that emphasized angular acceleration and deceleration. Patients who received the vestibular stimulation demonstrated greater improvement in functional ambulation than did patients who did not receive the stimulation.