Influence of different durations of lower limb static stretching on the performance of long jump athletes: a randomized controlled trial

Long Jump is an athletic (track and field) event that combines speed, strength and agility in an attempt to land as far away from the take-off point [1], being performed in 4 different phases: the run-up, take-off, flight and landing [2]. The athlete starts by sprinting, jumps up from a take-off board, and flies through the air before landing in a box of sand [2]. Previous research describing the biomechanics and electromyographic analysis of the long jump has shown the contribution of lower limb muscles during the different phases, especially the quadriceps muscles, the hamstrings, the gastrocnemius and the tibialis anterior [3, 4].

Warm-up prior to athletic events is considered essential to optimize performance. Traditional warm-up programs are typically composed of aerobic activity, sport-specific exercises and stretching. Specifically stretching, is considered an essential component of warm-up routines in athletic settings, as an increased flexibility has been linked to an increased range of motion and decreased incidence of injury, particularly of muscle injuries [5‐8]. This might be related to the viscoelastic effects of stretching. Indeed, previous investigations describe that an increase in joint range of motion is associated with a decrease in passive resistance to stretch, as a result of a reduction in muscle stiffness or an increase in muscle compliance [5, 9].

Static stretching (SS) involves lengthening a muscle until a stretch sensation or point of discomfort is reached, holding the muscle in a lengthened position for a period of time [7]. Despite the evidence regarding the effect of stretching on muscle injury prevention, several studies have been investigating the potential harms of SS on the performance of many athletes, with controversial results [5‐7, 10‐13]. On one hand, several adverse effects of SS have been pointed, such as a decrease in maximal strength, torque production and muscle activation [11, 14, 15]; and impaired sprint [6] and jump height performance [16]. On the other hand, other studies have described no detrimental effects on sprint or jump performance associated with prior SS in trained healthy athletes [12, 17]. However, the lack of impairment may be related to different factors like possible short durations of the SS, and stretches performed with an intensity less than the point of discomfort [10].

The effects of SS have been largely investigated in many sports and in different types of vertical jumps. Nevertheless, to date, no studies have described neither the effects of lower limb SS specifically on long jump athletes’ performance nor assessed the effects of different durations of SS. In this sense, this study aims to evaluate the influence of different durations of lower limb SS on the performance of long jump athletes.

The sample characterization regarding the variables age, weight, height, body mass index (BMI), years of track and field practice and the number of weekly training is described in Table 1.

Table 2 describes the intra- and inter-group comparisons of the athletes' performance in the long jump (in meters) before and after the 4 conditions of the study.

A significant change was observed only in the SS-3 min condition, showing an improvement in the distance achieved in the long jump (p = 0.012) between the two assessments. However, there were no significant differences between conditions both before (p = 0.284) and after the intervention (p = 0.154).

A raincloud plot illustrating the distribution of the differences in long jump performance can be seen in Fig. 2. It is possible to note that the group of SS-3 min was the only where most of the subjects had a positive influence after stretching. In the other groups, several subjects evidenced mostly a decrease in jump performance.

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The aim of this study was to evaluate the influence of different durations of lower limb SS on the performance of long jump athletes, with 3 different durations being studied (30 s, 1 min and 3 min).

Some mechanical and viscoelastic properties of muscles can be affected by SS. In a previous investigation with track and field athletes, it was demonstrated that after hamstrings SS, muscle elasticity worsened [26]. The authors suggested that the changes in elasticity caused a disturbance in the optimal distance between actin and myosin chains, affecting the ability to generate strength, speed and explosive power [26], which may justify the decreased performance in jump height described in the study. Indeed, an adequate muscle elasticity plays an important role in stretch–shortening cycle activities such as jumping, as it results in better energy conservation and in an enhanced released propulsive force [27]. Muscle stiffness also seems to be relevant in jump performance. Previous research has shown that higher stiffness favors fast stretch–shortening cycle activities and enhances explosive athletic performance in trained individuals [28], as muscle stiffness is positively related to the vertical ground reaction force [28]. Evidence from the investigations of Nakamura, Ikezoe [29] and Caliskan, Akkoc [30] shows a decrease in muscle stiffness after 5 min of SS of the gastrocnemius and rectus femoris, respectively, proposing that SS may impair jumping performance by also decreasing muscle stiffness.

The results of the present study are not in line with the previous evidence since it was revealed that in the conditions of SS of 30 s and 1 min there were no significant changes in performance. On the contrary, in the 3-min SS condition, there was even a significant improvement in the distance achieved in the long jump. However, considering the final assessment and the difference between the final and initial assessments, there were no differences between the 4 conditions of the study, including the control condition where no stretching was performed. These findings suggest that the improvement in performance after SS of lower limbs muscle groups for 3 min, may not be attributed to the stretching intervention. More likely, this improvement in performance can be attributed to the effect of warm-up. Indeed, the investigations of Holt and Lambourne [31] and Pagaduan, Pojskić [32] registered an improvement in jump performance after general warm-ups aiming to increase blood flow, heart rate and temperature in the muscles. In fact, previous evidence suggests that an increase in temperature can induce lower viscous resistance improving muscle contractility, and consequently, performance [33, 34].

A review from Behm and Chaouachi [10] aimed to investigate the negative, null or positive responses to stretching on performance. The authors reported impairments in studies who performed SS for different moderate durations, such as 90 s, 2 min, 3 min and over 5 min, whereas the mean percentage of impairments in strength and force was − 6.9%, exceeding the jump (− 2.7%) and sprint (− 2.4%) performance decrements. Specifically in vertical jump height, significantly higher impairments were also detected when performing SS for more than 90 s when compared to less than 90 s. In that sense, most of the included studies in this review let the authors to conclude that, in general, shorter durations of SS within a warm-up may not negatively impact performance in highly trained individuals, while durations longer than 90 s seem to introduce impairments.

Regarding the 30 s and 1 min SS, the conclusions of the review of Behm and Chaouachi [10] are in line with the results of the present study where, similarly, no detrimental effects on jump performance were detected for these conditions. On the other hand, conflicting results were found for the condition of 3 min of SS, since there was no loss of performance, and there was even an improvement in the jump distance, which is contradictory to the conclusions of Behm and Chaouachi [10] that SS longer than 90 s impairs jump performance. However, it should be noted that in this review, the focus was on vertical jumps and not on long jump performance, therefore, the factors or mechanisms that may contribute to the decrease in performance after SS in the vertical jump may be different from those for the long jump. Furthermore, most of the studies involved in the revision perform the SS in one muscle group, while the present study involved four lower limb’s muscle groups, which may also produce distinct effects. Nevertheless, as previously indicated, the improvement achieved after the 3-min SS, may not be attributed to SS, since no differences between conditions were noted.

The study of de Oliveira and Rama [12] used a wider stretching protocol with more muscle groups (triceps surae, quadriceps, hamstrings, gluteus maximus and quadratus lumborum). Although countermovement jumps were performed in this study, similar to our results, the authors reported no impairments in jump performance in healthy trained athletes after 30 s of SS.

The findings of the present study suggest no potential harms of SS when applied to the proposed lower limb muscles for 30 s, 1 min or 3 min to each muscle group. Nevertheless, some limitations should be recognized. First, the reduced sample size. Second, the fact that only the acute effects of SS on performance were assessed. Since the available literature is scarce, future research with more robust samples, and with more than one intervention session, should address the effects of more SS durations on long jump performance, and measure for how long possible changes in performance are maintained. Likewise, additional electromyographic analysis of the muscles submitted to SS would be important to understand which mechanisms or muscle changes SS cause.

The results of the present study suggest that SS performed for 30 s, 1 min or 3 min seem not to significantly influence the long jump performance in track and field athletes, since despite an improvement in the distance reached after the 3 min SS, there were no significant differences between conditions, including compared to control.