Background
Methods
Search strategy
Type of intervention: | AND | “exercise therapy” [MeSH Terms] OR “resistance training” [MeSH Terms] OR exercise OR strengthening OR shoes OR footwear OR barefoot OR foot ortho* OR insole* OR inlay* |
Target of intervention: | AND | doming OR “short foot” OR “foot core” OR foot musc* OR intrinsic foot OR plantar musc* OR toe musc* OR hallu* muscle |
Outcome measure: | AND | postur* balance OR postur* stability OR postur* control OR stance balance OR stance stability OR stance control OR dynamic* OR function* OR gait OR walking OR locomotion OR running |
Pathologies: | NOT | stroke OR “multiple sclerosis” OR “cerebral palsy” |
Selection criteria
-
a study population consisting of adults of all ages in the absence of a neuromuscular or neurological condition affecting lower extremity function severely and without any painful musculoskeletal complaints in the lower extremity. The latter is expected to interfere with exercise performance and is negatively associated with adherence [43];
-
studying the effect of noninvasive interventions anticipated to improve PIFM strength. As the focus is on strength, as opposed to neuromuscular adaptations, interventions had to last at least 4 weeks [38, 44]. These interventions include, for example but were not restricted to, 1) muscle strengthening programs composed of ‘short foot’ or ‘foot doming’ exercises or exercises requiring toe flexion muscle force (e.g., toe plantar flexion, towel curl exercise, marble pick up, heel raises) or toe ab−/adduction muscle force (e.g., toe spread out), 2) a transition from conventional to minimal shoe or barefoot condition;
-
reporting outcome measures, at least assessed at baseline and directly post intervention, that are related to the locomotor system’s function on balance control and propulsion. These measures should originate from the following domains: 1) dynamic balance (e.g., star excursion balance test), 2) foot and ankle biomechanics during gait or running (e.g., MLA kinematics, kinetics, plantar pressure, propulsive power of foot and ankle joints), 3) anterior and vertical ground reaction force (GRF) peak and impulse at push-off phase during gait or running and 4) spatiotemporal gait or running parameters.In addition, if the intervention targeted other muscles additional to the PIFMs (e.g., heel raises, foot and ankle exercise program, transition to minimal shoe or barefoot condition), then at least the outcome of one measure of purely PIFM strength (e.g., size or doming strength) should be reported, in order to be able to associate changes in dynamic outcome measures to changes in PIFM strength.
-
one of the following study designs: 1) a controlled trial in which one of the above mentioned interventions was the contrast between the trial arms (i.e., intervention A compared to intervention A + intervention of interest) or was compared with ‘no intervention’/ ‘placebo’ (e.g. stretching)/ ‘usual care’ (e.g., usual training regime), 2) a controlled trial in which at least one group received only the intervention of interest, but without an adequate control group as described in 1. This was considered as a pre-post interventional study in further analysis, and 3) a pre-post interventional study in which the study population received only the intervention of interest.
Selection process
Data extraction
Methodological quality assessment
Data analysis
Data synthesis
Results
Study selection
Characteristics of included studies
Intervention | Outcomes | ||||||||
---|---|---|---|---|---|---|---|---|---|
Study / Design | Methodo-logical quality | Study population gender: (male/female) age: mean ± sd | Type | Volume | Progression | Supervision | Adherence/attendance | Domain | Instruments and measures |
Taddei et al. [39] Randomized controlled trial | High | Long distance runners IG (n = 14) Gender: 5/9 Age: 41.9 ± 7.4 yr CG (n = 14) Gender: 9/5 Age: 41.6 ± 6.0 yr | I: Foot and ankle strength exercise program C: stretching program | 8 weeks 4 sessions 20–30 min | Customized, 3 levels (sitting, double leg, single leg stance) | Weekly supervised session | 80.4% supervised sessions attended | Barefoot running analysis with 3D motion capture system and force plates: | |
Foot and ankle biomechanics | MLA ROMb and stiffness; | ||||||||
Ground reaction forces | GRF verticala and AP impulse at push-off. | ||||||||
Okamura et al. [40] Randomized controlled trial | High | Pronated foot posture IG (n = 10) Gender: 1/9 Age: 19.7 ± 0.9 yr CG (n = 10) Gender: 2/8 Age: 20.2 ± 1.5 yr | I: Short-foot exercise program supported by electrical stimulation and EMG biofeedback C: No intervention | 8 weeks 3 sessions 3 sets 10 reps 5 s contraction 45 s rest between sets | Customized, 3 levels (sitting, double leg, single leg stance) | Initial 20-min training session, weekly supervised session | 102.1% unsupervised sessions accomplished; 77.5% supervised sessions attended | Barefoot gait analysis with 3D motion capture system and force plates: | |
Foot and ankle biomechanics | Navicular dropa and corresponding moment in time; | ||||||||
Ground reaction forces | GRF (anterior, medial, verticalc) in second half of stance; | ||||||||
Spatiotemporal parameters | Stance phase duration. | ||||||||
Matsumoto et al. [58] Pre-post intervention study | Low | n = 20 Gender: 10/10 Age: 20.0 ± 2.4 yr | I: Short-foot exercise program | 4 weeks # sessions NR 30 reps 5 s contraction | Fixed, 3 levels: wk. 1 – sitting wk. 2 – double leg stance wk. 3 to 4 – single leg stance | Initial 30-min training session | 67.2% sessions accomplished | Barfoot gait analysis with 3D motion capture system and pressure plate: | |
Foot and ankle biomechanics | MLA compressiona, peak pressure per foot region, total plantar contact area; | ||||||||
Spatiotemporal parameters | Gait speed. | ||||||||
Lynn et al. [53] Randomized controlled trial | High | IG (n = 8) Gender: 3/5 Age: 23.7 ± 2.1 CG (n = 8) Gender: 3/5 Age: 22.6 ± 1.7 yr | I: Short-foot exercise program C: No intervention | 4 weeks daily 100 reps 5 s contraction | Fixed, 2 levels: week 1,2 – sitting week 3,4 – double leg stance | Initial training session, weekly phone consult, extra instructional training session before week 3 | NR | Dynamic balance | YBT mediolateral CoP excursion for dominant and non-dominantc stance leg |
Lee and Choi [54] Randomized controlled trial | Moderate | Chronic ankle instability IG (n = 15) Gender: 5/10 Age: 20.9 ± 1.1 yr CG (n = 15) Gender: 5/10 Age: 20.8 ± 0.9 yr | I: IFM strength exercise program C: no intervention | 6 weeks 3 sessions 3 blocks 4 sets 3–15 reps 3–20s contraction | Fixed, 3 levels:week 1,2 – sitting week 3,4 – double leg stance week 5,6 – single leg stance | Supervision, but not specified | NR | Dynamic balance | YBT composite reach distance normalized to leg length |
Mulligan et al. [56] Pre-post intervention study | Moderate | n = 21 Gender: 3/18 Age: 26.1 ± 3.7 | Short-foot exercise program | 4 weeks daily 3 min 5 s contraction | Customized, 3 levels (sitting, double leg, single leg stance) + variations (vision, surface stability) | Initial 1-h training session | 85.7% sessions accomplished | Dynamic balance | SEBT reach distance in five directions, among which mediala |
Tudpor et al. [55] Non-randomized controlled trial | Low | Diabetes IG (n = 8) Gender: 4/4 Age: 62.6 ± 0.4 yr CG (n = 7) Gender: 3/4 Age: 67.4 ± 0.5 yr | I: foot strength exercises + short-foot exercises C: foot strength exercises | 8 weeks daily IG 30 reps of foot exercises + 30 min SFE CG 30 reps of foot exercises | No progression, sitting position | NR | NR | Dynamic balance | SEBT reach distance normalized to leg length in eight directions, among which laterala |
Lee et al. [57] Pre-post intervention study | Low | Chronic ankle instability (n = 15) Gender: 7/8 Age: 21.5 ± 2.5 yr | Short-foot exercise program | 8 weeks 3 sessions 3 sets 12 reps 5 s contraction | 2 levels, fixed: week 1 to 4 – sitting weeks 5 to 8 – single leg stance | NR | NR | Dynamic balance | Moving platform: overall and medio-laterala center of gravity displacement index score |
Ma et al. [61] Pre-post intervention study | Low | Chronic ankle instability (n = 14) Gender: 6/8 Age: 20.3 ± 1.5 yr | Short-foot exercise program + sham transcranial direct current stimulation | 4 weeks 3 sessions 20 min 4 sets | 3 levels (sitting, double leg, single leg stance) | All sessions were supervised | NR | Dynamic balance | YBT composite reach distance normalized to leg length |
Kim et al. [59] Pre-post intervention study | Low | Pronated foot function (n = 7) Gender: 6/1 Age: 24.0 ± 1.9 yr | Short-foot exercise program | 5 weeks 3 sessions 30 min | No progression, sitting position | Initial training session, all sessions were supervised | NR | Dynamic balance | YBT composite reach distance normalized to leg length |
Pisal et al. [60] Pre-post intervention study | Low | Pronated foot posture (n = 40) Gender: NR Age: NR | Short-foot exercise program | 4 weeks daily 100 reps 5 s contraction | NR | NR | NR | Dynamic balance | YBT reach distance of both legs in three directions, among which posterolateral with the right legd |
Quality assessment
Reporting | Internal validity | |||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 27 | Total reporting (max. 12) | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | Total Internal validity (max. 13) | |
Taddei et al. [39] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 1 | 0 | 10 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 12 |
Okamura et al. [40] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 1 | 1 | 11 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 11 |
Lynn et al. [54] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 1 | 0 | 0 | 9 | 0 | 0 | 1 | 1 | 1 | 0a | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 9 |
Lee and Choi [55] | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 6 | 0 | 0 | 1 | 1 | 1 | 0a | 1 | 1 | 1 | 1 | 0 | 0a | 0a | 7 |
Mulligan et al. [57] | 1 | 1 | 1 | 1 | 0b | 1 | 1 | 0 | 1 | 1 | 0 | 8 | 0 | 0b | 1 | 0b | 1 | 1 | 1 | 0b | 0b | 0b | 0b | 0b | 1 | 5 |
Tudpor et al. [56] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 6 | 0 | 0 | 1 | 1 | 1 | 0a | 0a | 1 | 0 | 0b | 0b | 0a | 0 | 4 |
Lee et al. [58] | 0 | 1 | 0 | 0 | 0b | 1 | 1 | 0 | 1 | 1 | 1 | 6 | 0 | 0b | 1 | 0b | 1 | 0a | 1 | 0b | 0b | 0b | 0b | 0b | 1 | 4 |
Ma et al. [62] | 1 | 1 | 1 | 1 | 0b | 0 | 1 | 1 | 1 | 1 | 1 | 9 | 0 | 0b | 1 | 0b | 1 | 0a | 1 | 0b | 0b | 0b | 0b | 0b | 1 | 4 |
Matsumoto et al. [59] | 0 | 1 | 1 | 0 | 0b | 1 | 1 | 0 | 0 | 1 | 0 | 5 | 0 | 0b | 1 | 0b | 1 | 0a | 1 | 0b | 0b | 0b | 0b | 0b | 0a | 3 |
Kim et al. [60] | 0 | 1 | 1 | 0 | 0b | 0 | 1 | 0 | 0 | 0 | 0 | 3 | 0 | 0b | 1 | 0b | 1 | 0a | 1 | 0b | 0b | 0b | 0b | 0b | 0a | 3 |
Pisal et al. [61] | 0 | 0 | 0 | 0 | 0b | 1 | 1 | 0 | 0 | 1 | 1 | 4 | 0 | 0b | 1 | 0b | 0a | 0a | 1 | 0b | 0b | 0b | 0b | 0b | 0a | 2 |
Data synthesis
Intervention group | Control group | Intervention vs. control group | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Study / Design | Methodological quality | Outcome domain | Selected outcome measure | Baseline Mean ± sd | Follow-up Mean ± sd | Within group mean difference | Within group SMD | Baseline Mean ± sd | Follow-up Mean ± sd | Between group difference in change from baseline | Between group SMD in change from baseline c | Narrative summary of findings on PIFM strength |
Taddei et al. [39] Randomized controlled trial | High | Foot and ankle biomechanics | MLA ROM (°) | 4.2 ± 2.4 | 3.6 ± 2.3 | −0.6 | 0.26 | 4.6 ± 2.2 | 4.6 ± 1.8 | −0.6 | 0.26 | MRI assessed PIFM volume was significantly increased in IG as opposed to CG, whereas CSA and toe plantar flexion strength remained unchanged |
Ground reaction forces | GRF vertical impulse in second half of stance (N·s) | 65.9 ± 7.9 | 67.9 ± 6.5 | 2.0 | 0.28NR | 74.3 ± 7.0 | 73.5 ± 6.5 | 2.8 | 0.37† | |||
Okamura et al. [40] Randomized controlled trial | High | Foot and ankle biomechanics | Navicular drop (mm) | 6.2 ± 1.7 | 6.2 ± 1.5 | 0.0 | 0.00 | 5.9 ± 2.6 | 5.4 ± 2.5 | 0.5 | − 0.23 | US assessed PIFM thickness in IG and CG remained unchanged |
Ground reaction forces | GRF vertical in second half of stance (% BW) | 109.1 ± 4.5 | 108.3 ± 5.7 | −0.8 | −0.16 | 107.5 ± 6.2 | 108.4 ± 6.5 | −1.7 | −0.31 | |||
Spatiotemporal parameters | Stance phase duration (ms) | 610.1 ± 36.8 | 600.4 ± 34.5 | −9.7 | 0.27 | 623.6 ± 36.8 | 618.8 ± 47.1 | −4.9 | 0.13 | |||
Matsumoto et al. [58] Pre-post intervention study | Low | Foot and ankle biomechanics | MLA compression (°) | 3.72 ± 6.8 | 3.65 ± 9.8 | −0.07 | 0.01 | n/a | n/a | n/a | n/a | Toe grip strength in IG was significantly increased |
Spatiotemporal parameters | Gait speed (m/s) | 0.33 ± 0.02 | 0.33 ± 0.04 | 0.00 | 0.00 | n/a | n/a | n/a | n/a | |||
Lynn et al. [53] Randomized controlled trial | High | Dynamic balance | YBT mediolateral CoP excursion for non-dominant stance leg (mm) | 52.4 ± 4.5 | 43.1 ± 5.1 | −9.3 | 1.83* | 47.8 ± 7.8 | 48.1 ± 5.5 | −9.6 | 1.43† | n/a |
Lee and Choi [54] Randomized controlled trial | Moderate | Dynamic balance | YBT composite reach distance (% leg length) | 66.8 ± 9.6 | 70.9 ± 8.7 | 6.1b | 0.66* | 65.4 ± 8.7 | 66.7 ± 9.1 | 3.8b | 0.41† | n/a |
Mulligan et al. [56] Pre-post intervention study | Moderate | Dynamic balance | SEBT reach distance in medial direction (cm) | 57.8 ± 7.4 | 61.6 ± 6.6 | 3.8 | 0.54* | n/a | n/a | n/a | n/a | n/a |
Tudpor et al. [55] Non-randomized controlled trial | Low | Dynamic balance | SEBT reach distance in the lateral direction (% leg length) | 54.8 ± 5.4a | 53.6 ± 9.6a | −1.2 | −0.15 | 59.0 ± 9.5a | 55.6 ± 6.9a | 2.2 | 0.27 | n/a |
Lee et al. [57] Pre-post intervention study | Low | Dynamic balance | Medio-lateral center of gravity displacement index score as a response to a moving platform | 3.4 ± 1.0 | 1.5 ± 0.8 | −1.9 | 1.98NR | n/a | n/a | n/a | n/a | n/a |
Ma et al. [61] Pre-post intervention study | Low | Dynamic balance | YBT composite reach distance (% leg length) | 97.0d ± 7.5a,d | 96.0d ± 7.5a,d | −1.0 | −0.13 | n/a | n/a | n/a | n/a | n/a |
Kim et al. [59] Pre-post intervention study | Low | Dynamic balance | YBT composite reach distance (% leg length) | 74.3 ± 8.3 | 82.4 ± 7.4 | 8.1 | 0.97* | n/a | n/a | n/a | n/a | n/a |
Pisal et al. [60] Pre-post intervention study | Low | Dynamic balance | YBT reach distance of right leg in posterolateral direction | 61.1 ± 5.2 | 65.1 ± 5.1 | 4.0 | 0.78* | n/a | n/a | n/a | n/a | n/a |