Search Strategy and Reported Quality

The initial search identified 4602 titles. Following removal of duplicate publications, titles of 2320 publications were evaluated. The full text of 54 articles were retrieved, and 37 studies were identified for inclusion (see Fig. 1). Thirty-three studies investigated the immediate effects of changing step rate on performance and biomechanics, and four studies evaluated the longer-term effects of changing step rate on injury and biomechanics. The primary reasons for exclusion of studies were combined running retraining strategies [15,16,17,18], and manipulation of step length with no change in step rate [19,20,21]. In addition to data being extracted directly from the 37 included studies where possible, additional data were provided by 5 authors upon request [22,23,24,25,26].

Fig. 1
figure 1

PRISMA flow diagram for the selection of studies.

Characteristics of the 37 included studies are given in Table 1. The results of the Downs and Black Quality Index scores for each study are shown in Table 2. Of the 37 included studies, 17 were high quality [22, 27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42], 19 were moderate quality [23, 25, 26, 43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58], and 1 was low quality [24].

Table 1 Characteristics of included studies
Table 2 Downs and Black Quality Index results for each study

Primary Outcomes

Injury

Two studies [23, 55] were identified evaluating pain and function with a change in running step rate over time periods of 4 weeks to 3 months. One study investigated the effects of a 10% increase in step rate on pain and function in recreational runners with patellofemoral pain (1MQ [23]), providing limited evidence of improvements in total running distance per week, longest run pain-free, numeric pain rating scale, and Lower Extremity Functional Scale at 4 weeks and 3 months. The remaining study investigated the effects of a 7.5% increase in step rate on pain and function in recreational runners with patellofemoral pain (1MQ [55]), providing limited evidence of improvements in average pain, worst pain, and the Kujala Scale at 6 weeks. No data pooling was possible for any injury variables. All SMDs and CI for the four variables and associated time periods are shown in Table 3.

Table 3 Single study results for injury variables

Performance

Five studies [26, 42, 49, 50, 53] were identified evaluating the immediate differences in surrogate measures of performance with a change in running step rate.

Subjective Measures of Performance

Two studies were identified evaluating subjective measures of performance [49, 50]. In recreational runners, compared to running with a preferred step rate: very limited evidence indicated an increase in rate of perceived exertion (RPE) with a 10% increase in step rate, but no differences were reported with a 5% increase in step rate, or with 5% or 10% reductions in step rate (1MQ [48]); and very limited evidence indicated an increase in self-reported awkwardness and effort with a 10% increase in step rate (1MQ [49]).

Physiological Measures of Performance

Three studies were identified evaluating physiological measures of running performance [26, 42, 53]. In recreational runners, compared to running with a preferred step rate, very limited evidence indicated an increase in VO2 consumption when running at 3.13 m/s and 3.58 m/s with a 15% decrease in step rate [53]. Very limited evidence indicated no difference in VO2 consumption when: running at 4.02 m/s with a 15% decrease in step rate [53]; running at 3.13 m/s, 3.58 m/s and 4.02 m/s with a 15% increase in step rate [53]; and, running at maximum speed for a 1-h run with a 4% and 8% increase or decrease in step rate [42]. Very limited evidence indicated an increase in metabolic energy consumption with an 8% decrease, 15% decrease and 15% increase in step rate, while no difference was observed with an 8% increase in step rate [26]. No data pooling was possible for any performance findings as no measure of performance was reported by multiple studies. All SMDs and CI from single studies are shown in Table 4.

Table 4 Single study results for performance variables

Secondary Outcome

In the main manuscript, only the pooled results from two or more studies are presented for biomechanical variables. All SMDs and CI, including those from single studies are shown in Tables 5, 6, 7, 8, 9,10, 11, with all significant biomechanical findings additionally shown in Fig. 2. Unless stated otherwise, all reported findings are immediate effects to a change in running step rate.

Table 5 Pooled and single study results for spatiotemporal gait parameters
Table 6 Pooled and single study results for ground reaction force and loading rate variables
Table 7 Pooled and single study results for kinetic, kinematic and muscle activation variables at the foot, ankle and lower leg
Table 8 Pooled and single study results for kinetic, kinematic and muscle activation variables at the knee
Table 9 Pooled and single study results for kinetic, kinematic and muscle activation variables at the
hip
Table 10 Pooled and single study results for kinetic, kinematic and muscle activation variables at trunk and pelvis
Table 11 Segment coordination and coordination variability results from single studies
Fig. 2
figure 2

Significant biomechanical variables with changes in running step rate. Note: Changes in running step rate are provided in brackets next to each biomechanical variable (e.g. + 10% = 10% increase in habitual running step rate). Effect size of change is indicated by the colour of the text used to note the percentage change in running step rate (e.g. + 10% in red = small effect size with a 10% increase in habitual running step rate; orange = medium effect size; green = large effect size). AV average, AVLR average vertical loading rate, BF bicep femoris, COM centre of mass, DF dorsiflexion, GLUTE MAX gluteus maximus, GLUTE MED gluteus medius, GLUTE MIN gluteus minimus, IR internal rotation, IVLR instantaneous vertical loading rate, PFJ patellofemoral joint, PF plantarflexion, PROX proximal, RF rectus femoris, SAG sagittal, SEG segment, SMEM semimembranosus, TA tibialis anterior, TRANS transverse, VGRF verticl ground reaction orce, VL vasus lateralis

Biomechanics

Twenty-two studies [10, 12,13,14, 18,19,20,21,22,23,24,25, 28, 30, 32, 33, 35, 37,38,39, 42, 45] were identified evaluating biomechanical differences between running with a preferred step rate and an increased step rate, and 13 studies [12,13,14, 19, 20, 24, 25, 28, 32, 33, 37, 39, 42] were identified evaluating biomechanical differences between running with a preferred step rate and a reduced step rate. A total of 221 variables were evaluated (Tables 5, 6, 7, 8, 9,10, 11).

Spatiotemporal Gait Parameters

Nine studies [24, 26, 30, 33, 44, 45, 49, 54, 57] were identified evaluating running spatiotemporal gait parameters. Eight studies [26, 30, 33, 44, 45, 49, 54, 57] evaluated differences in gait parameters between running with a preferred step rate and an increased step rate, while seven studies [24, 26, 30, 44, 45, 49, 54] evaluated differences between running with a preferred step rate and a reduced step rate.

Step length: In recreational runners, compared to running with a preferred step rate: moderate evidence indicated a shorter step length with a 10% increase in step rate (2HQ [30, 33] and 2MQ [44, 49]; 0.93, 0.49 to 1.37; I2 = 52%); and moderate evidence indicated a longer step length with a 10% reduction in step rate (1HQ [30], 2MQ [44, 49] and 1LQ [24]; − 0.76, − 1.31 to − 0.21; I2 = 70%).

Contact time: In recreational runners, compared to running with a preferred step rate: limited evidence indicated no difference in contact time with a 10% increase in step rate (1HQ [30] and 1MQ [45]; 0.50, -0.02 to 1.03; I2 = 0%); and limited evidence indicated an increase in contact time with a 10% reduction in step rate (1HQ [30] and 1MQ [45]; − 0.95, − 1.49 to − 0.40; I2 = 0%).

Ground Reaction Forces, Loading Rates and Braking Impulse

Ten studies [25, 30, 31, 33, 38, 41, 44, 49, 50, 54] were identified evaluating ground reaction force and loading rate variables. All studies evaluated biomechanical differences between running with a preferred step rate and an increased step rate, while six studies [25, 30, 31, 44, 49, 54] evaluated biomechanical differences between running with a preferred step rate and a reduced step rate.

Ground reaction forces: In recreational runners, increasing step rate by 10% was associated with limited evidence of no difference in peak vertical ground reaction force (1HQ [33] and 1MQ [49]; 0.24, -0.11 to 0.59; I2 = 0%).

Loading rates: In recreational runners, increasing running step rate by 10% was associated with no difference in average vertical loading rate (1HQ [41] and 1MQ [50]; 0.24, − 0.23 to 0.70; I2 = 0%) and vertical instantaneous loading rate (1HQ [41] and 1MQ [50]; − 0.04, − 0.50 to 0.42; I2 = 0%).

Braking impulse: In recreational runners, reducing step rate by 10% was associated with limited evidence of increased braking impulse (1HQ [30] and 1MQ [49]; − 0.73, − 1.08 to − 0.37; I2 = 0%).

Foot, Ankle, and Lower Leg

Nineteen studies [22, 26, 30,31,32,33,34,35,36, 38, 39, 41, 44, 45, 47, 49, 50, 54, 57] evaluated 81 biomechanical variables at the foot, ankle, and lower leg. All studies evaluated biomechanical differences between running with a preferred step rate and an increased step rate, while ten studies [26, 30, 31, 35, 36, 39, 44, 45, 49, 54] also evaluated biomechanical differences between running with a preferred step rate and a reduced step rate.

Kinetics: In recreational runners, increasing step rate by 10% was associated with moderate evidence of no difference in peak tibial acceleration (2HQ [31, 41] and 2MQ [44, 50]; 0.06, − 0.29 to 0.42; I2 = 8%); and limited evidence of no difference in negative ankle work (2 MQ [44, 49]; − 0.01, − 0.36 to 0.33; I2 = 0%). Increasing step rate by 5% was associated with moderate evidence of no difference in rearfoot peak pressure (2HQ; 0.18, − 0.15 to 0.51; I2 = 0%) and rearfoot contact time (2HQ; − 0.07, − 0.41 to 0.26; I2 = 0%).

In recreational runners, reducing step rate by 10% was associated with limited evidence of increased negative ankle work (2 MQ [44, 49];−  0.38, − 0.73 to − 0.03; I2 = 0%) and no difference in peak tibial acceleration (1HQ [31] and 1 MQ [44]; − 0.42, − 0.93 to 0.08; I2 = 0%). Reducing step rate by 5% was associated with moderate evidence of no difference in rearfoot peak pressure (2HQ [35, 39]; − 0.14, − 0.48 to 0.19; I2 = 0%), rearfoot max force (2HQ; − 0.14, − 0.47 to 0.19; I2 = 0%), and rearfoot contact time (2HQ [35, 39]; − 0.23, − 0.56 to 0.10; I2 = 0%).

Kinematics: In recreational runners, increasing step rate by 10% was associated with moderate evidence of reduced foot strike angle (2HQ [22, 33] and 1MQ [49]; 0.62, 0.34 to 0.09; I2 = 0%); and limited evidence of no difference in average plantar/dorsiflexion at initial contact (1HQ [34] and 1MQ [45]; 0.23, − 0.20 to 0.67; I2 = 0%). Increasing step rate by 5% was associated with limited evidence of reduced foot strike angle (1HQ [22] and 1MQ [49]; 0.39, 0.09 to 0.69; I2 = 0%).

Knee

Fourteen studies [23, 26, 29, 30, 32,33,34, 36, 38, 44, 45, 47, 49, 51, 55] evaluated 64 biomechanical variables at the knee. All studies evaluated biomechanical differences between running with a preferred step rate and an increased step rate, while seven studies [26, 30, 36, 44, 45, 49, 51] also evaluated biomechanical differences between running with a preferred step rate and a reduced step rate.

Kinetics: In recreational runners, increasing step rate by 10% was associated with moderate evidence of reduced peak knee extensor moment (2HQ [29, 33] and 1MQ [49]; 0.50, 0.18 to 0.81; I2 = 0%); and limited evidence of reduced peak patellofemoral joint stress (2HQ [29, 33]; 0.56, 0.07 to 1.05; I2 = 0%) and reduced negative knee work (2 MQ [44, 49]; 0.84, 1.20 to 0.48; I2 = 0%). In recreational runners, reducing step rate by 10% was associated with limited evidence of reduced negative knee work (2 MQ [44, 49]; 0.88, 0.52 to 1.25; I2 = 0%).

Kinematics: In recreational runners, increasing step rate by 10% was associated with strong evidence of reduced peak knee flexion angle (3HQ [29, 33, 34] and 2MQ [47, 49]; 0.66, 0.40 to 0.92; I2 = 0%); and moderate evidence of no difference in average knee flexion at initial contact (1HQ [34] and 2MQ [45, 49]; − 0.23, − 0.53 to 0.07; I2 = 0%). Increasing step rate by 5% was associated with limited evidence of no difference in average knee flexion at initial contact (2 MQ [45, 49]; − 0.19, − 0.57 to 0.18; I2 = 0%).

In recreational runners, reducing step rate by 10% was associated with limited evidence of no difference in average knee flexion at initial contact (2 MQ [45, 49]; 0.18, − 0.20 to 0.55; I2 = 0%). Reducing step rate by 5% was associated with limited evidence of no difference in average knee flexion at initial contact (2 MQ [45, 49]; 0.15, − 0.22 to 0.53; I2 = 0%).

Hip

Thirteen studies [23, 24, 26, 32,33,34, 36, 38, 41, 44, 45, 49, 51, 55] evaluated 67 biomechanical variables at the hip. Twelve studies [23, 26, 32,33,34, 36, 38, 41, 44, 45, 49, 51, 55] evaluated biomechanical differences between running with a preferred step rate and an increased step rate, while seven studies [24, 26, 36, 44, 45, 49, 51] evaluated biomechanical differences between running with a preferred step rate and a reduced step rate.

Kinetics: In recreational runners, increasing step rate by 10% was associated with limited evidence of reduced negative hip work (2 MQ [44, 49]; 0.55, 0.91 to 0.20; I2 = 0%). In recreational runners, reducing step rate by 10% was associated with limited evidence of increased negative hip work (2 MQ [44, 49]; − 0.67, − 1.02 to − 0.31; I2 = 0%).

Kinematics: In recreational runners, increasing step rate by 10% was associated with moderate evidence of reduced peak hip adduction during stance phase (2HQ [34, 41] and 1MQ [49]; 0.40, 0.11 to 0.69; I2 = 0%); and limited evidence of reduced peak hip flexion during stance phase (1HQ [34] and 1MQ [49]; 0.42, 0.10 to 0.75; I2 = 0%), no difference in average hip flexion at initial contact (1HQ [34] and 1MQ [45]; 0.14, − 0.29 to 0.57; I2 = 0%) and no difference in peak hip internal rotation during stance phase (1HQ [34] and 1MQ [49]; 0.07, − 0.25 to 0.38; I2 = 0%).

Trunk and Pelvis

Five studies [23, 24, 33, 34, 44] evaluated five biomechanical variables at the trunk and pelvis (Table 10). Four studies [23, 33, 34, 44] evaluated biomechanical differences between running with a preferred step rate and an increased step rate, while two studies [24, 44] evaluated biomechanical differences between running with a preferred step rate and a reduced step rate.

Kinetics: No data pooling was possible for any trunk or pelvis kinetic findings.

Kinematics: In recreational runners, increasing step rate by 10% was associated with moderate evidence of no difference in average trunk flexion during stance phase (2 HQ [33, 34]; 0.00, − 0.39 to 0.39; I2 = 0%).

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