Sheldon Knight and Dr. Brent Feland, Physical Education
Many studies have compared the different variable of stretching: duration of stretch, intensity of stretch, method, frequency, and modalities with stretch (i.e. heat and or cold). Stretching has been shown to improve flexibility, or increase range of motion, injury prevention, enhance muscle performance, promotion of healing, and possibly decreased symptoms of delayed onset muscle soreness, and improved running economy. Modalities—heat and or cold—combined with stretch have provided varied results with flexibility. Heat with stretching may or may not provide adequate results. In some studies, cold with stretch was found to be more beneficial than heat with stretch. Few studies have determined the effect of diathermy and static stretch on increasing hamstring flexibility.
The purpose of this study is to determine if diathermy combined with a longer duration stretch (10 minutes) improves hamstring flexibility more than stretching without diathermy or no stretching. My hypothesis is there will be no difference in flexibility improvement between the three groups (diathermy and stretch, sham diathermy and stretch, and control).
Twenty-two adults over the age of 30 were used for this study. In order to qualify for participation, subjects needed to exhibit tight hamstrings (the inability to achieve greater than 160o of knee extension at 900 of hip flexion). Other exclusion criteria included: (1) pregnancy, (2) previous lower back or hamstring injury, (3) metal plates, pins, or screws present in the right lower extremity, (4) acute muscle soreness of the hamstring, (5) a pacemaker, or (6) discomfort during data collection that the researchers conclude as more than normal. All subjects were assigned a number in order to maintain subject confidentiality. The subjects were required to read and sign an informed consent form that described the risks, benefits, and procedures of the study, along with his or her right to discontinue involvement in the study. Three subjects did not qualify due to too much flexibility, one subject opted not to participate once study was explained, and two subjects did not return after first treatment. Each subject was asked to arrive in attire that allowed for unhindered access to the hamstring muscle group were assigned to one of 3 groups: (1) stretch and diathermy (heat), (2) stretch and sham diathermy (no-heat), and (3) control
The final sample size consisted of 9 participants in the heat group, 8 in the no-heat group, and 3 in the control group. The average age was 48.4 + 12.3, ranging from 30 to 69 years. During the treatment time, with all subjects within the treatment groups, no statistical difference existed between them when comparing starting ROM values. When comparing stretching improvement during the treatment period, the participants in the control group showed virtually no change while those in the heat and no-heat groups showed a significant improvement in flexibility.
However, no statistical difference existed in the rate of change of ROM between the treatment groups. The only statistical difference existed between the control group and the treatment groups. After the treatment period, the control group showed no change. Those within the heat group showed a greater rate of change than the other groups throughout the treatment period but the results were not statistically significant. Those in the no-heat group showed minimal change. When comparing the groups, no statistical difference existed between the groups.
The results support previous findings that stretching does indeed increase flexibility, or joint range of motion. In this study, subjects were measure for flexibility prior to and after treatment each day. The average increase in flexibility from pre to post for each day was 4.3o for the noheat group, 4.22o for the heat group, and 0o for the control group.
Research suggests that warming the muscle previous to stretching can increase the flexibility of the muscles. Funk et al1 reported the results from the use of a heat pack prior to short-duration stretching. The study group used moist heat packs for 20 minutes and then stretched the hamstring muscle for 30 seconds. The researchers concluded that significant results in hamstring flexibility could be obtained by using moist heat packs. Henricson et al2 reported that heat combined with stretching of the hamstring on hip ROM resulted in a greater increase in flexibility than stretching alone. The results however were not statistically significant. Draper et al3, Peres et al4, Wessling et al5 reported the use of diathermy in warming the muscle to tendons to produce the effects. The Draper, Peres, and Wessling studies show that deep heat and stretching were more effective in increasing flexibility than stretching alone. Our results differ from those exhibited by the Funk, Henricson, Draper, Peres, and Wessling studies
It is possible that our results do not show a statistically significant difference between heat and no-heat due to the population sample size. It is also possible that our results differ from those from the Draper et al, Peres et al, Wessling et al, and the animal studies because our subjects came from an older population. Physiological changes occur as people age: muscle atrophy, reduced capacity for healing with diminished capillary blood supply and reduced amounts of mesenchymal stem cells, and loss of soft tissue and collagen elasticity and strength. Muscles exhibit a greater resistance to change and therefore joint mobility and ROM decrease due to increased amounts of fibrous connective tissue. Feland6 et al reported that more physically active seniors are more flexible. The authors also reported that stretches of longer duration improved flexibility better than short duration stretches in an older population. Stretching has been shown to aid all ages. Since our subjects were of an older age, the diathermy may not have had any effect on helping flexibility due to the collagen deposition and change in physiology attributed to old age.
- Efficacy of moist heat pack application over static stretching on hamstring flexibility. J Strength Cond Res. 2001; 15(1):126-132.
- The effect of heat and stretching on range of hip motion. J Orthop Sports Phys Ther. 1984;6:110-115.
- Immediate and residual changes in dorsiflexion range of motion using and ultrasound heat and stretch routine. J Athl Train. 1998;33:141-144.
- Pulsed shortwave diathermy and prolonged long-duration stretch increase dorsiflexion range of motion more than identical stretching without diatherm. J Athl Train. 2002;37:43-50.
- Effects of static stretch versus static stretch and ultrasound combined on triceps surae muscle extensibility in healthy women. Phys Ther. 1987;67:674-679.
- The effect of duration of stretching of the hamstring muscle group for increasing range of motion in people 65 years or older. Phys Ther. 2001;81(5):1110-1117.