Table 4.
Strength of evidence for associated modifiable factors (cross-sectional studies) included in qualitative synthesis.
| Associated Modifiable Factor | Study | Study Quality | Positive Findings | Level of Evidence |
|---|---|---|---|---|
| Anthropometrics | ||||
|
| ||||
| Waist Circumference | Van der Worp et al. (2012) | Low | No | No evidence. |
|
| ||||
| Hip Circumference | Van der Worp et al. (2012) | Low | No | No evidence. |
|
| ||||
| Waist-to-hip Ratio | Van der Worp et al. (2012) | Low | No | No evidence. |
|
| ||||
| Joint Range-of-Motion and Muscle Length | ||||
|
| ||||
| Ankle Dorsiflexion ROM | Crossley et al. (2007) | Moderate | No | Conflicting evidence for decreased ankle dorsiflexion ROM. |
| Malliaras et al. (2006) | Low | Yes | ||
| Scattone Silva et al. (2016) | Low | Yes | ||
|
| ||||
| Posterior Thigh Flexibility | Crosley et al. (2007) | Moderate | Yes | Conflicting evidence for both increased and decreased posterior thigh flexibility. |
| Malliaras et al. (2006) | Low | No | ||
| Scattone Silva et al. (2016) | Low | Yes | ||
|
| ||||
| Quadriceps Flexibility | Scattone Silva et al. (2016) | Low | No | No evidence. |
|
| ||||
| Knee Extension ROM | Kujala et al. (1986) | Low | No | No evidence. |
|
| ||||
| Sports and Activity Related Factors | ||||
|
| ||||
| Strength Training Volume | Lian et al. (2005) | High | Yes | Moderate evidence for greater volume of strength training per week. |
| Lian et al. (2003) | Moderate | Yes | ||
|
| ||||
| Jump Training Volume | Lian et al. (2005) | High | No | Conflicting evidence for greater volume of jump training per week. |
| Lian et al. (2003) | Moderate | Yes | ||
|
| ||||
| Sport Surface | Bode et al. (2017) | Low | No | No evidence. |
| Ferretti et al. (1984) | Low | Not Tested | ||
| Krauss et al. (2007) | Low | No | ||
| van der Worp et al. (2012) | Low | No | ||
|
| ||||
| Running Workouts per Week | Krauss et al. (2007) | Low | No | No evidence. |
|
| ||||
| Weekly Running Mileage | Krauss et al. (2007) | Low | No | No evidence. |
|
| ||||
| Running Speed | Krauss et al. (2007) | Low | Yes | Limited evidence for running at a slower average pace. |
|
| ||||
| Impact Profile of Sport | Longo et al. (2011) | Low | No | No evidence. |
|
| ||||
| Sport Specific Training Volume | Lian et al. (2003) | Moderate | No | No evidence. |
|
| ||||
| Quantity of Stretching Before or After Training | Lian et al. (2003) | Moderate | No | No evidence. |
|
| ||||
| Shoe Type | Bode et al. (2017) | Low | No | No evidence. |
|
| ||||
| Insole Use | Bode et al. (2017) | Low | No | No evidence. |
|
| ||||
| Functional Testing | ||||
|
| ||||
| Standing Jump Height | Lian et al. (1996) | High | Yes | Conflicting evidence for greater standing jump height with a 20-kg load. No evidence for greater jump height without an external load or with a ½ BW load. |
| Lian et al. (2003) | Moderate | No | ||
|
| ||||
| Standing Jump Work | Lian et al. (1996) | High | Yes | Conflicting evidence for greater work performed during the standing jump. |
| Lian et al. (2003) | Moderate | No | ||
|
| ||||
| Average Force during Standing Jump | Lian et al. (2003) | Moderate | Yes | Limited evidence for greater average force during a standing jump with a ½-BW or a 1-BW load. |
|
| ||||
| Average Power During Standing Jump | Lian et al. (2003) | Moderate | Yes | Limited evidence for greater average power during a standing jump with a ½-BW or a 1-BW load. |
|
| ||||
| Average Velocity During Standing Jump | Lian et al. (2003) | Moderate | No | No evidence. |
|
| ||||
| CMJ Work | Lian et al. (1996) | High | Yes | Conflicting evidence for greater CMJ work. |
| Lian et al. (2003) | Moderate | No | ||
|
| ||||
| Drop CMJ Work | Lian et al. (2003) | Moderate | Yes | Limited evidence for greater drop CMJ work from a 45 cm height. |
|
| ||||
| CMJ-Standing Jump Height | Lian et al. (1996) | High | Yes | Conflicting evidence for greater CMJ-standing jump height. |
| Lian et al. (2003) | Moderate | No | ||
|
| ||||
| Average Power on 15-Second Rebound Test | Lian et al. (1996) | High | Yes | Conflicting evidence for greater average power on the 15-second rebound. |
| Lian et al. (2003) | Moderate | No | ||
|
| ||||
| Jump Test Composite Score | Lian et al. (2003) | Moderate | Yes | Limited evidence for better performance on a battery of jump tests. |
|
| ||||
| 6-Meter Hop Test Time | Crossley et al. (2007) | Moderate | No | No evidence. |
|
| ||||
| Hop for Distance | Crossley et al. (2007) | Moderate | No | No evidence. |
|
| ||||
| Muscle Performance | ||||
|
| ||||
| Knee Flexion Torque | Dauty et al. (2007) | Low | No | No evidence. |
| Krauss et al. (2007) | Low | No | ||
| Kujala et al. (1986) | Low | No | ||
|
| ||||
| Plantarflexion Endurance | Crossley et al. (2007) | Moderate | No | No evidence. |
| Malliaras et al. (2006) | Low | No | ||
|
| ||||
| Normalized Peak Plantarflexion Torque | Scattone Silva et al. (2016) | Low | No | No evidence. |
|
| ||||
| Knee Extension Fatigue Ratio | Dauty et al. (2007) | Low | Yes | Limited evidence for decreased knee extension fatigue ratio. |
|
| ||||
| Knee Flexion Fatigue Ratio | Dauty et al. (2007) | Low | No | No evidence. |
|
| ||||
| Knee Extension Eccentric Endurance Quotient | Krauss et al. (2007) | Low | Not Tested | No evidence. |
|
| ||||
| Knee Flexion Eccentric Endurance Quotient | Krauss et al. (2007) | Low | Not Tested | No evidence. |
|
| ||||
| Concentric Hamstring to Quadriceps Quotient | Krauss et al. (2007) | Low | No | No evidence. |
|
| ||||
| Normalized Peak Hip Extension Torque | Scattone Silva et al. (2016) | Low | Yes | Limited evidence for decreased normalized hip extension torque. |
|
| ||||
| Stimulus Response Curve for the Motor Evoked Potential of the Quadriceps | Rio et al. (2016) | High | Yes | Moderate evidence for a steeper slope to the motor evoked potential curve for the quadriceps. |
|
| ||||
| Occupational Demands | ||||
|
| ||||
| Occupational Classification | van der Worp et al. (2011) | Low | Yes | Limited evidence for heavy physically demanding work. |
|
| ||||
| Knee Loading During Work | van der Worp et al. (2011) | Low | No | No evidence. |
ROM = Range-of-motion, BW = Bodyweight, CMJ = Counter-movement jump