1 Introduction
There has been an extensive body of literature published on the effects of static stretching (SS) as a component of a warm-up prior to activity as well as chronic training effects. Publications from the mid-1990s to the present have reported on acute SS-induced performance impairments with both the stretched muscle [
1‐
5] as well as contralateral non-stretched muscles [
6]. However, the previously cited reviews as well as original investigations [
7‐
9] have highlighted that when SS is limited to no more than 60 s per muscle group and incorporated into a full warm-up that includes prior aerobic activity and subsequent dynamic stretching (DS) and activity, the effects on subsequent performance are typically trivial. Nevertheless, there has been a paradigm shift away from SS towards a greater emphasis on DS [
1,
2,
5].
Dynamic stretching has been described as an action that involves controlled movement through the active joint range of motion (ROM) [
1,
2,
10] with repeated cyclical muscle loading (tension associated with achieving end ROM) and unloading (muscle relaxation through mid-ROM) [
10]. This shift towards more DS is based on evidence indicating that in several studies, a single bout of DS can provide similar [
11‐
13] or even greater [
14,
15] increases in ROM than SS. In regard to chronic effects, whereas one study reported more than double the ROM improvements with SS versus DS training [
16], another did not report any significant difference [
17]. However, there are other articles that indicate that an acute session of SS is superior to DS for promoting ROM increases [
18‐
22].
A perceived benefit of DS is the lack of subsequent performance impairments or even augmented performance [
1,
2,
23,
24]. Positive performance effects may be attributed to the dynamic movement effects on reflex-induced neuromuscular excitation (i.e., muscle spindle reflex activity), increased corticospinal activity, enhanced persistent inward currents (amplification of motor output), increased enzymatic cycling due to muscle contraction-induced increases in muscle temperature, and increased active muscle stiffness among other factors [
1,
2,
24]. The literature is fragmented with reports of acute DS-induced performance increases [
25‐
29], no significant change [
30‐
35] as well as decrements [
36,
37]. Concerning DS chronic effects, ten sessions of DS training over 3 weeks resulted in no significant effects on hamstrings eccentric torque or triple-hop distance [
38]. Thus, the literature is not consistent on the greater potential of DS versus SS on improving ROM or enhancing performance.
A historically perceived benefit of SS was its purported benefits for decreasing the incidence of injuries [
24,
39,
40]. However, this issue was fractious as well, with reports that enhanced flexibility reduced all-cause injury incidence [
41,
42] but longitudinal training studies [
43] and some reviews [
44,
45] reported a lack of significant reduction in all-cause injury risk in response to chronic SS. Later reviews [
1,
40,
46‐
48] stipulated that while SS was unlikely to decrease all-cause injury incidence, there was evidence for a reduction in musculotendinous injuries, especially with explosive and change of direction movements. While SS-induced changes in injury incidence have been well debated, there is a lack of literature on the effect of DS on injury incidence. Furthermore, is it necessary to dynamically move a joint through a full ROM (DS) or would dynamic activity involving movement through a partial ROM have a positive effect on injury incidence? Hence, the objective of this narrative review was to survey the literature on injury incidence with DS or dynamic activity incorporated into a pre-activity warm-up, by considering possible moderating variables such as ROM, strength, balance, proprioception, muscle morphology, and psycho-physiological responses.
3 Injury Incidence
Based on the concept of training specificity [
50], several papers suggest that DS is preferable to SS as part of a warm-up because of the similarity to movements that occur during subsequent exercises [
1,
2]. In our search, we found only two articles that investigated the effect of DS alone on injury incidence. In one study, the DS program (17 injuries, 1.42 ± 1.49 injuries/team) showed no significant differences compared to a DS + SS program (20 injuries, 2.0 ± 1.24 injuries/team) among 465 high school soccer players [
49]. Zakaria et al. [
49] concluded that SS does not provide additional benefit to DS and furthermore DS with soccer-specific movements without SS may be adequate for injury prevention in high school boy soccer players. A second study examining the effects of functional dance-specific DS training recruited 60 sport dancers (competitive ballroom dancing) with a history of ankle injuries who trained twice a week for 8 weeks with 45-min sessions [
51]. The DS training significantly (
p < 0.01) improved ankle joint stability. However, there are several other papers (17 studies: see Table
1) showing the effectiveness of incorporating both DS and dynamic activities together within a warm-up to reduce injury incidence.
Table 1
Effect of multifaceted dynamic activity on the injury incidence/rate
Al Attar et al., 2021 [ 63] | M | 31.6 ± 4.1 | 200 | FIFA 11+ (running with hip out and in, circling and jumping, plank, Nordic hamstrings, squat, jumping, bounding, cutting, technique) | 6 months (2 d/w) [20–25 min/session] | Amateur soccer referees | R | IG: 9 injuries CG: 24 injuries CG: (1.45 injuries/1000 exposure hours) IG: (0.50 injuries/1000 exposure hours), 65% ↓ injuries |
| M | 19.8 ± 1.5 | 319 | FIFA 11+ | 7 months (3 d/w) [20–25 min/session] | Amateur soccer players | R | IG: 163 (52%) injuries CG: 200 (63%) injuries IG = ↓ (injury RR = 0.6; 95% CI 0.5–0.8) |
Slauterbeck et al., 2019 [ 57] | M–F | High school | 3611 | FIFA 11+ | 1 year (1 d/w) [20–25 min/session] | High school athlete | R | IG: 196 injuries CG: 172 injuries (1.59 and 1.47 injuries per 1000 athlete exposures, respectively; p = 0.771) No significant difference |
Silvers-Granelli et al., 2015 [ 65] | M | 18–25 | 1625 | FIFA 11+ | 8 months (3 d/w) [20–25 min/session] | Division II collegiate | R | IG: 285 injuries CG: 665 injuries IG = 8.09 injuries per 1000 CG = 15.04 injuries per 1000 |
| M | 14–19 | 416 | FIFA 11+ | 6 months (2 d/w) [15–20 min/session] | Premier soccer league division | R | IG: 36 injuries CG: 94 injuries IG overall injury rate ↓ 41% [injury RR: = 0.59 (95% CI 0.40–0.86; p = 0.006)] |
Hammes et al., (2014) [ 58] | M | ≥ 32 | 265 | FIFA 11+ | 9 months (1 d/w) [20–25 min/session] | Elite soccer players | R | IG: 51 injuries CG: 37 injuries No significant difference |
Steffen et al., 2013 [ 59] | F | 13–18 | 385 | FIFA 11+ | 4 months (2–3 d/w) [20–25 min/session] | Elite soccer players | R | High adherence to the 11 + 57% ↓ injury (injury IRR 0.43, 95% CI 0.19–1.00) compared with low adherence No significant difference |
| M | 18–25 | 41 | FIFA 11+ | 12 weeks (5–6 d/w) [20–25 min/session] | Collegiate soccer players | R | Referent season: 8.1 injuries per 1000 exposures (13 injuries) Intervention season: 2.2 injuries per 1000 exposures (4 injuries) Intervention season 72% ↓ relative injury risk (RR 0.28, 95% CI 0.09–0.85) |
Soligard et al., 2008 [ 55] | F | 13–17 | 1892 | FIFA 11+ | 8 months (2 d/w) [20–25 min/session] | Regional districts players | R | IG: 161 injuries CG: 215 injuries IG = overall injury ↓ (0.68, 0.48–0.98) |
| M | 7–14 | 962 p | FIFA 11 + Kids (jogging, hopping, balance, strength and core stability exercises, technique) | 6 months (2 d/w) [15–20 min/session] | Elite soccer players | R | IG = 30 injuries CG = 60 injuries IG 50% ↓ compared with CG (RR 0.50; 95% CI 0.32–0.78) |
Rossler et al., 2018 [ 54] | M-F | 10.8 ± 1.4 | 3895 | FIFA 11 + Kids | 1 season (2 d/w) [15–20 min/session] | Elite soccer players | R | IG = 139 injuries CG = 235 injuries IG = overall injury rate 48% ↓ (hazard ratio 0.52; 95% CI 0.32–0.86) |
Beaudouin et al., 2018 [ 60] | M-F | 10.8 ± 1.4 | 3895 | FIFA 11 + Kids | 1 season (2 d/w) [15–20 min/session] | Elite soccer players | R | IG = 58% injury ↓, per 1000 football hours 0.15 (95% CI 0.10–0.23) CG = injuries per 1000 football hours 0.33 (95% CI 0.25–0.43) IG = ↓ severe overall (HR 0.42, 95% CI 0.24–0.72), match (0.41, 0.17–0.95) and training injuries (0.42, 0.21–0.86) |
Al Attar et al., 2021 [ 68] | M | 18–31 | 726 | FIFA 11 + S (running, throw the ball, spinning hands, external and internal rotation, scaption, push-up, shoulder and biceps dumbbell exercises) | 6 months (2 d/w) [15 min/session] | Amateur goal keepers | | IG: 50 injuries CG: 122 injuries IG = (0.62 injuries per 1000 exposure-hours), CG = (1.94 injuries/1000 h) 68% ↓ in IG (injury RR = 0.32, 95% CI 0.27–0.34) |
van de Hoef et al., 2019 [ 61] | M | 18–45 | 400 | Bounding exercise program (walking lunges, triplings + drop, lunges, bounding) | 12 weeks (2 d/w) [3–5 min/session] | First‐class amateur league | R | IG: 31 injuries CG: 26 injuries IG = 1.12/1000 hamstring injuries hours CG = 1.39/1000 injuries hours No significant differences (OR = 0.89, 95% CI 0.46–1.75) |
Richmond et al., 2016 [ 70] | M/F | 11–15 | 275 | Neuromuscular training (aerobic; forward and backward running, zigzag and sideway shuffles; strength, balance, and agility) | 12 weeks (2–3 d/w) [15 min/session] | Junior high school | R | IG: 26 injuries CG: 60 injuries IG = injuries ↓ (injury RR 0.30, 95% CI 0.19–0.49) |
| F | 12–17 | 4582 | Knäkontroll, SISU Idrottsböcker (one-legged knee squat, pelvic lift, two-legged knee squat, the bench, the lunge, and jumping) | 7 months (2 d/w) [15 min/session] | Elite soccer players | R | IG: 7 injuries CG: 14 injuries IG: injuries ↓ 64% (injury RR 0.36, 95% CI 0.15–0.85) |
| F | 13–19 | 1506 | HarmoKnee (static stretching exercises, jogging; forward and backward running, Defensive pressure technique and high-knee skipping; balance and core-stability exercises) | 4 months (2 d/w) [20–25 min/session] | Regular regional soccer players | R | IG = 3 injuries CG = 13 injuries IG = injuries ↓ 77% decrease IG = incidence rates of 0.04 per 1000 player hours CG = 0.20 per 1000 player hours |
Dynamic stretching involves dynamic movements such as shoulder rotation, trunk rotation, hip flexion, extension, abduction or adduction, high knee lifts, and other movements through a full ROM under control [
1,
2,
10,
52]. In contrast, dynamic activities such as running, jumping, and landing can differ from DS in that their primary objective may not be to move through a full ROM. Dynamic activities are typically included in multi-faceted exercise programs, which aim to acutely improve strength, balance, and core stability specific to the sport for which one is preparing. Consequently, it can be assumed that sports involving intermittent, non-continuous, bouncing, and jumping exercises with a high intensity of stretch–shortening cycles (e.g., soccer, basketball, handball, and North American football) need a muscle tendon unit that is sufficiently compliant to store and release elastic energy to improve performance [
53] and hence, likely decreases injuries. Moreover, multiple factors interact to sustain injury, and hence, multi-faceted programs that encompass a wide range of exercise elements have shown efficacy for injury prevention [
54‐
56]. The most effective programs tend to incorporate dynamic activities and stabilization exercises as they follow the concept of training or action specificity [
50]. Recently, multi-faceted warm-up programs such as the FIFA 11+, the FIFA 11 + Kids, the FIFA 11 + S, the HarmoKnee, the Knäkontroll, SISU Idrottsböcker, neuromuscular training (NMT) program, and bounding exercise program have been implemented as intervention programs to decrease injuries among athletes. These warm-up programs typically involve only a few exercises that dynamically move through a full or nearly full ROM (e.g., lunges, high knee lifts, scaption, hip internal and external rotations while walking). Hence, there is a greater emphasis on dynamic activities than DS.
The FIFA 11+ injury prevention program is a multi-faceted (e.g., DS, jumping, running, bounding, agility, balance, core stability) dynamic activity program (see Tables
1,
2) [
54,
57‐
62]. Six of nine studies that performed this program at least two times per week (20–25 min each session) instead of a conventional warm-up program found that the FIFA 11+ program was effective in reducing injury incidence/rate among soccer players [
55,
63‐
67] (Table
1). Three studies showed no significant effect of this program on injury incidence. Interestingly, two of these studies reporting non-significant effects performed this program only once per week. An age-specific warm-up and injury prevention program for children “FIFA 11 + Kids” has been performed two times per week (15–20 min each session) instead of a regular warm-up program in three studies [
54,
60,
62]. These studies found a significant injury reduction (48% [
54], 50% [
62], and 58% [
60] overall injury rate reductions) among players. The FIFA 11 + S focuses on the reduction of upper extremity injuries among players with more overhead movements. Al Attar et al. [
68] showed a 68% reduction in overall injury incidence among male goalkeepers following the FIFA 11 + S. After incorporating the Knäkontroll, SISU Idrottsböcker program for 7 months, twice per week (15 min each session), Waldén et al. [
69] reported that anterior cruciate ligament injuries were reduced by 64% (rate ratio 0.36, 95% confidence interval 0.15–0.85) in adolescent female soccer players. Another dynamic exercise program is NMT, which is designed to increase strength, proprioception, balance, and movement technique by incorporating several different exercises [
70]. Richmond et al. [
70] revealed that 12 weeks (two to three times per week, 15 min each session) of a high-intensity NMT program (i.e., aerobic, strength, balance, and agility components) reduced sport injury risk (rate ratio 0.30, 95% confidence interval 0.19–0.49; 26 injuries in the NMT group compared with 60 injuries in the control group) in junior high school students [
70]. A 4 months (two times per week, 20–25 min each session), the HarmoKnee warm-up group (three injuries in the HarmoKnee group compared with 13 in the control group) was associated with a 77% decrease in knee injuries [
56]. Thus, this research tends to suggest that dynamic warm-up activities that may not necessarily emphasize movement to the endpoints of the ROM can still contribute to a reduced injury incidence.
Table 2
Exercise elements of multifaceted programs
FIFA 11+ | × | × | × | × | × | × | × | 9 studies 6 positive effects |
FIFA 11 + Kids | × | × | × | × | – | × | × | 3 studies 3 positive effects |
FIFA 11 + S | × | × | – | – | – | × | – | 1 study Positive effect |
BEP | – | × | | × | – | × | – | 1 study No effect |
NMT | × | × | × | × | × | × | – | 1 study Positive effect |
Knäkontroll, SISU Idrottsböcker | – | × | × | × | – | × | – | 1 study Positive effect |
HarmoKnee | × | × | × | × | × | × | – | 1 study Positive effect |
Brunner and colleagues [
71] in a meta-analysis reported that multi-faceted exercise programs were effective in reducing the injury incidence of lower extremities, but not groin injuries. Moreover, they found that multi-faceted injury prevention protocols are more effective compared with single-component prevention protocols [
71]. Table
1 highlights 17 original articles [
54‐
70], from which were found 13 studies [
54‐
56,
60,
62‐
70] with five different programs, reporting that multi-component exercise interventions (strength, balance, plyometric, and dynamic warm-up/stretching) (Table
2) were effective in reducing lower extremity injuries. The most frequent elements of a multi-faceted training program were a combination of strength, balance, plyometric, and dynamic warm-up/stretching exercises, which enhanced the effect of an injury prevention program. It can be speculated that the combination of these elements can improve flexibility [
71]. For example, a recent meta-analysis reported that resistance training (e.g., free weights, machines, elastic resistance bands, and Pilates) can induce moderate magnitude improvements in ROM [
72]. Dynamic activities, such as running and jumping that incorporate a stretch–shortening cycle, use an eccentric muscle contraction to store elastic energy to enhance a subsequent explosive concentric contraction [
73]. Dynamic activities can decrease active muscle stiffness and increase utilization of elastic strain energy in the more compliant muscle–tendon unit [
73], improving movement efficiency within the obtainable ROM. It is suggested that multi-component dynamic activity and DS can significantly reduce the incidence/rate of injuries among athletes.
5 Conclusions
The paradigm shift in the twenty-first century from SS to DS may be attributed to DS-induced improvements in ROM with either a lack of negative or even positive effects on performance. Whereas only two articles investigated the effects of DS, there is extensive evidence showing the positive injury attenuation effects of activity programs incorporating DS and dynamic activity (i.e., FIFA 11+, FIFA 11 + Kids, FIFA 11 + S, HarmoKnee, Knäkontroll, SISU Idrottsböcker, NMT). An acute bout of DS can increase strength with a trivial-to-small magnitude, while DS training studies demonstrate conflicting effects on strength, balance, and proprioception. In addition, there are also conflicting reports on the acute and chronic effects of DS on MTU stiffness. In both acute and chronic conditions, DS can result in a decrease, no change, or even an increase in muscle/MTU stiffness. While increases in strength and MTU compliance could augment the ability to absorb higher forces and torques, decreasing the chances for MTU injury, there is a lack of clarity regarding whether DS-induced alterations (or a lack of alterations) in strength, balance, MTU stiffness, and compliance can prevent injuries. Acute bouts of DS may induce thixotropic effects (reduced viscoelasticity) and positively modify the emotional state, attenuating muscle tension, while the psychological benefits may also increase concentration, attention, and better prepare players for games and competition. With the preponderance of conflicting findings, the paradigm shift from SS to DS for performance enhancement and injury reduction is lacking in consistent evidence and more in-depth research is necessary to validate its benefits.