Comparison of the effects of static stretching on range of motion and jump height between quadriceps, hamstrings and triceps surae in collegiate basketball players

Subjects

Fourteen collegiate basketball players (14 men, 20.2±0.7 years, 179.0±5.0 cm, 71.9±8.3 kg) were recruited for this study because they have a higher level of proficiency of jumping than athletes of other sports. Subjects with a history of lower-limb injuries within 1 year were excluded. All subjects were informed of the requirements and risks associated with their involvement in this study.

Experimental approach to the problem

The study was conducted on three separate days with all participants undergoing one of three different conditions each day, and the participants received the three different SS in random order. The targeted muscles of the SS were the quadriceps, hamstrings and triceps surae. Before and after each session of SS, ROM and vertical jump height were measured. All experiments were completed in the same room, in which the temperature was maintained at 25°C.

Measurement of ROM

ROM was measured by using the dominant leg. The dominant leg was determined by asking which leg they use to kick a ball as fast as possible.16 ROM was defined as one at which the participants were able to have a maximally tolerable angle without pain. A digital inclinometer (DL164V; Survey Techno-Science, Japan) was used to measure ROM. The digital inclinometer was placed at the mid-point of the anterior tibial border, between the tibial tuberosity and the anterior joint line of the ankle.17 The methods of measuring ROM are shown in figure 1.

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Measurement of vertical jump height

After measurement of ROM, the participants performed three submaximal vertical jump trials as warm-ups. After the submaximal trials, the participants performed three maximal effort vertical jump trials, with a 30 s rest interval between each trial. The greatest value of the three maximum trials was used for the analyses.

Static stretching

All SS was performed in 1 set of 5 min on each of the dominant and non-dominant legs, in random order, because the minimum time for an increase in flexibility differs between the muscles (hamstrings need 3 min, triceps surae needs 2 min, quadriceps is unknown) and 5 min of SS may increase the flexibility of the three muscles. The participants were instructed to be relaxed during SS. The posture of each stretch is shown in figure 2.

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Statistical analyses

All data were described as mean±SD. Before using parametric tests, the assumption of normality was verified using the Kolmogorov-Smirnov test. A paired t-test was used to compare the difference of ROM and vertical jump height between before and after values for each muscle. A one-way analysis of variance was used to examine the difference of relative change in ROM and vertical jump height between muscles. When a significant difference was found, post hoc analyses using Tukey’s test was performed. SPSS statistics V.25 was used for all statistical analyses. Differences were considered statistically significant at an alpha level of p<0.05.

Range of motion

ROM was increased in all muscles (all p<0.05) (table 1). There was no significant difference in the relative change in ROM (p<0.05) (table 1).

Vertical jump height

In the quadriceps (p=0.35) and hamstrings (p=0.22), the vertical jump height indicated no change, while it decreased in the triceps surae (p<0.01) (table 2). There was a significant difference in the relative change of the vertical jump height (p<0.05, partial η²=0.28), and post hoc analyses indicated that the change in the triceps surae was a lower value than those of other muscles (p<0.05) (table 2).

In the present study, the sample size was not evaluated in advance. Therefore, we calculated the actual power from the effect size of the relative change of vertical jump height using G*power18 at a setting of α=0.05 and a sample size of 14. The results indicated that the statistical power was sufficient (0.98).

Changes in ROM

The present study showed that ROM increased without any difference between the muscles, while vertical jump height significantly decreased after SS of only the triceps surae. The effective duration of SS required to decrease passive properties differs between each muscle.9–11 Nakamura et al reported that SS for more than 2 min is effective in increasing the extensibility of the gastrocnemius muscle.10 Matsuo et al9 and Nakamura et al11 reported that more than 3 min of SS is effective on decrement in passive stiffness of the hamstrings. To our best knowledge, the effective duration of SS for the quadriceps is unclear. Therefore, the present study used SS for 5 min because it may increase muscle extensibility in these three muscles. Kataura et al19 reported that the intensity of SS is related to the relative change in muscle–tendon unit stiffness, which indicated that the intensity of SS has an impact on its effects. Because the three muscles targeted in the present study have different characteristics in volume, cross-sectional area and shape, it is very difficult to perform SS at the same intensity. Therefore, in this study, the intensity of SS was decided as the maximum angle at which the participants felt no pain. In this study, ROM of the three muscles was increased after 5 min of SS without significant difference in relative changes in ROM between the muscles. These data indicated that SS for 5 min at the maximum angle increased ROM, regardless of the muscle.

Changes in vertical jump height

In this study, 5 min of SS of the triceps surae decreased vertical jump height by 3.3%, while it showed no change in the quadriceps and hamstrings. Behm and Chaouachi12 reported that a decrement in jump performance after SS was affected by the duration of SS, and SS for more than 90 s decreases jump performance by 3.3%. These results indicated that the results of the present study are consistent with the previous study. There are limited studies that have examined the effects of SS for single muscles on the alteration of jump performance. Guissard and Reiles15 showed vertical jump height indicated no change after SS of the quadriceps for 6 min. On the other hand, Cornwell et al16 and Fletcher and Jones20 reported that vertical jump height was decreased after SS of the triceps surae for 6 and 1.5 min, respectively. To our best knowledge, there is no study that has examined the effects of SS of the hamstrings on jump performance. However, Lim and Park21 reported that a foam roller exercise on the hamstrings increased ROM, but vertical jump performance showed no change. The elasticity of the Achilles tendon plays an important role in jump performance.22 A previous study showed that tendon stiffness decreased after 5 min of SS for the triceps surae.23 These findings suggested that it is possible that SS for the triceps surae decreased vertical jump height because of decrement in Achilles tendon stiffness.

Jump height is very important for basketball players, but they need various types of performance, such as sprinting and agility. The muscles required for each movement are different. Therefore, it is necessary to show the effects of SS on various types of performance.