Table 1 Summary of studies

AST H:Q ratio

Eustace et al. 2017 [37]

To compare PT and AST H:Q ratio (FR) between limbs, angles and velocities

26 male professional soccer players

PT H:Q ratio and AST H:Q ratio at 10° angles from 40 to 70° (0° = full knee extension) at three different isokinetic velocities (60, 180, and 270°/s) on the dominant and non-dominant legs

PT H:Q ratio was greater for the dominant than the non-dominant leg, and increased with higher velocities. AST H:Q ratio was greater for the dominant than the non-dominant leg at angles 60°, 50°, and 40°

Eustace et al. 2018 [38]

To compare PT and AST H:Q ratio (FR) between senior professional and youth soccer players

17 senior professional and 17 elite youth male soccer players

PT H:Q ratio and AST H:Q ratio at ten degree angles from 40 to 70° (0° = full knee extension) at three different isokinetic velocities (60, 180 and 270°/s) on the dominant and non-dominant legs

PT H:Q ratio was greater for the dominant than the non-dominant limb and increased with higher velocities similarly for both groups. AST H:Q ratio was greater at 70° and 60° on the non-dominant leg for youth compared to senior players

Aagaard et al. 1998 [3]

To assess PT and AST H:Q ratio (CR and FR) at different angles and velocities

9 track and field athletes (5 males and 4 females)

PT H:Q ratio and AST H:Q ratio at 50°, 40°, and 30° of knee flexion (0° full knee extension) at two different isokinetic velocities (30 and 240°/s)

PT and AST H:Q ratio (FR) increased across movement velocities and at extended knee joint angles. AST H:Q ratio (CR) increased across extended knee joint angles. PT H:Q ratio (CR) was not affected by velocity

El-Ashker et al. 2017 [27]

To investigate sex differences on PT and AST H:Q ratio (FR)

96 young adults (50 males and 46 females)

PT H:Q ratio and AST H:Q ratio at 15°, 30°, and 45° of knee extension (0° = full knee extension) at three different isokinetic velocities (60, 180 and 300°/s)

PT H:Q ratio was lower for females compared to males. PT and AST H:Q ratio decreased for both groups with increased isokinetic velocity and close to full knee extension

Cohen et al. 2015 [28]

To investigate the effect of simulated soccer on PT and AST H:Q ratio (FR)

9 semi-professional male soccer players

PT H:Q ratio and AST H:Q ratio at 9 knee flexion angles (from 10 to 90°; 0° = full knee extension) at 120°/s

Simulated soccer led to reduced PT H:Q ratio. Additionally, there was an AST H:Q ratio decrease at 10° of knee flexion

Hiemstra et al. 2004 [36]

To compare PT and AST H:Q ratio (CR and FR) at different angles, velocities and contraction types between hamstring tendon ACL reconstruction and uninjured control participants

16 participants (9 males and 7 females) with more than 1 year of hamstring tendon ACL reconstruction and 30 active uninjured males

PT H:Q ratio and AST H:Q ratio measured from 5 to 95° of knee flexion (0° = full knee extension) at five angular velocities (50, 100, 150, 200, and 250°/s). Strength maps were used for comparisons between groups

Participants with ACL reconstruction had overall lower PT H:Q ratio compared to active participants, and presented lower AST H:Q ratio near full knee flexion and higher AST H:Q ratio near full knee extension

Huang et al. 2017 [33]

To investigate PT and AST H:Q ratio (CR and FR) in participants with unilateral and symptomatic ACL deficiency

46 male participants with unilateral chronic ACL-rupture

PT H:Q ratio and AST H:Q ratio at 6 knee flexion angles (from 30 to 80° of knee flexion; 0° = full knee extension) on ACL deficiency and uninvolved (healthy) limbs at 60°/s

There was no difference between groups for PT H:Q ratio. ACL deficiency limbs presented greater AST H:Q ratio compared to healthy limbs at 30° and 40° of knee flexion

De Ste Croix et al. 2017 [29]

To investigate sex differences on PT and AST H:Q ratio (FR) measured at different angles and velocities

55 male and 55 female recreationally active participants

PT H:Q ratio and AST H:Q ratio at three knee flexion angles (15, 30, and 45°, 0° = full knee extension) and three angular velocities (60, 120, and 240°/s)

PT H:Q ratio was lower at 120°/s and 240°/s and AST H:Q ratio was lower at 15° and 30° of knee flexion in females compared to males

Ayala et al. 2012 [35]

To determine the absolute reliability of the PT and AST H:Q ratio (CR and FR)

50 recreational athletes (26 males and 24 females)

PT H:Q, AST H:Q ratio at three different joint angles (10°, 20°, 30°), and ROM-specific torque H:Q ratios at 4 different ranges (0–10°, 11–20°, 21–30°, and 0–30°) of knee flexion measured on three different occasions

PT H:Q ratio presented moderate reliability values. AST and joint ROM-specific torque H:Q ratios demonstrated poor absolute reliability scores

Evangelidis et al. 2015 [5]

To compare PT, isometric, and AST H:Q ratio between soccer players and recreationally active males

10 soccer players and 14 recreationally active males

PT H:Q ratio, isometric H:Q ratio at five angles (105°, 120°, 135°, 150°, and 165°) and AST H:Q ratio at five angles (from 100 to 160° for 60°/s; from 105 to 160° for 240°/s; and from 115 to 145° for 400°/s)

PT, isometric and AST H:Q ratios were similar between professional soccer players and recreationally active players at any velocity

RTD H:Q ratio

Zebis et al. 2011 [45]

To compare the RTD H:Q ratio with isometric H:Q ratio

23 elite soccer players (11 females and 12 males)

Isometric H:Q ratio and RTD H:Q ratio at incrementing time periods of 10 ms (from 0 to 250 ms)

RTD H:Q ratio from 0 to 50 ms was lower than isometric H:Q ratio

Greco et al. 2012 [39]

To compare PT H:Q ratio (CR) and RTD H:Q ratio in soccer players with high and low strength levels

39 male professional soccer players

PT H:Q ratio and RTD H:Q ratio calculated at a time interval of 0–50 ms

Soccer players who had high strength levels had greater PT H:Q ratio and RTD H:Q ratio compared to counterparts with low strength levels. There was no correlation between ratios

Hannah et al. 2014 [41]

To compare isometric H:Q ratio and RTD H:Q ratio

20 untrained males

Isometric H:Q ratio and RTD H:Q ratio at time intervals of 25, 50, 75, 100, and 150 ms of force onset

RTD H:Q ratio was lower than isometric H:Q ratio

Hannah et al. 2015 [30]

To investigate sex differences on isometric H:Q ratio and RTD H:Q ratio

40 untrained adults (20 males and 20 female)

Isometric H:Q ratio and RTD H:Q ratio calculated at time intervals of 25, 50, 75, 100, and 150 ms of force onset

Isometric H:Q ratio was greater in males than females. RTD H:Q ratio was similar between sexes at each time point

Jordan et al. 2015 [42]

To investigate RTD H:Q ratio in elite ski racers

29 elite alpine ski racers (13 males and 8 females uninjured and 3 males and 5 females with ACL reconstruction)

RTD H:Q ratio calculated at time intervals of 0–50, 0–100, 0–150, and 0–200 ms

Elite alpine ski racers with ACL reconstruction had greater RTD H:Q ratio at 0-50 ms compared to uninjured counterparts

Palmer et al. 2017 [43]

To examine the effects of age on isometric H:Q ratio and RTD H:Q ratio

15 young and 15 older women

Isometric H:Q ratio and RTD H:Q ratio at time intervals of 0–30 and 0–200 ms

Older women had greater RTD H:Q ratio at 0–200 ms compared to young women

Greco et al. 2013 [40]

To investigate the effect of a fatiguing soccer-specific exercise on H:Q ratio (CR and FR) and RTD H:Q ratio

22 male professional soccer players

PT H:Q ratio at 180°/s and RTD H:Q ratio at time intervals of 0–50 and 0–100 ms

The fatiguing soccer-specific exercise led to lower PT H:Q ratio, but there was no effect on RTD H:Q ratio

Thorlund et al. 2008 [44]

To investigate the effect of a simulated handball match on isometric H:Q ratio and RTD H:Q ratio

10 male elite handball players

Isometric, and RTD and RTD impulse H:Q ratios at time intervals of 30, 50, 100, and 200 of force onset

The simulated handball match did not lead to changes on isometric H:Q ratio, but RTD and RTD impulse H:Q ratios increased at 0–30 ms

FI H:Q ratio

Pinto et al. 2018 [52]

To investigate the influence of neuromuscular fatigue on PT H:Q ratio (CR) and the association between FI H:Q ratio and PT H:Q ratio

35 male elite professional soccer players

PT H:Q ratio and FI H:Q ratio at 300°/s

FI H:Q ratio was greater and weakly correlated to PT H:Q ratio. PT H:Q ratio only declined in the last three repetitions of the fatigue test, which was strongly correlated to hamstring torque decreases, but weakly correlated to quadriceps torque decreases

Costa et al. 2018 [51]

To investigate the effect of hamstrings stretching and fatigue on H:Q ratio (CR) and FI H:Q ratio

35 healthy adults (17 females and 18 males)

PT H:Q ratio and FI H:Q ratio at 180°/s

There was no effect of combined stretching and fatigue on PT and FI H:Q ratios

MS H:Q ratio

Denadai et al. 2016 [47]

To investigate the association between PT H:Q ratio (CR) and MS H:Q ratio

9 male professional soccer players

PT H:Q ratio at 60°/s and MS H:Q ratio

PT H:Q ratio did not significantly correlate with MS H:Q ratio

Evangelidis et al. 2016 [48]

To investigate the association between PT H:Q ratio (FR), isometric H:Q ratio and MS H:Q ratio

31 recreationally active young men

PT H:Q ratio at 50 and 350°/s, isometric PT H:Q ratio, and MS H:Q ratio

MS H:Q ratio was positively correlated with isometric H:Q ratio and PT H:Q ratio at both velocities

Wieschhoff et al. 2017 [50]

To compare a MS VM:SM ratio between patients with ACL tears and participants with no ACL abnormalities

100 ACL tear and 100 control participants without ACL abnormalities (54 male and 46 female in each group)

MS VM:SM ratio

MS VM:SM ratio of patients that had recent non-contact ACL injuries was greater than control participants without ACL abnormalities

Behan et al. 2018 [46]

To investigate sex differences on MS H:Q ratio

66 healthy active young (32 males and 34 females)

MS H:Q ratio

MS H:Q ratio was lower in females compared to males

Ruas et al. 2017 [49]

To compare 3 different resistance training protocols involving concentric and eccentric muscle actions on MS H:Q ratio

Forty untrained males

MS H:Q ratio

No resistance training protocol led to any changes on MS H:Q ratio

MA H:Q ratio

Aagaard et al. 2000 [53]

To investigate the amount of antagonist coactivation during maximal quadriceps contraction and assess the MA H:Q ratio

60 sedentary males

MA (EMG-moment) H:Q ratio at 30°/s

Hamstrings coactivation and MA H:Q ratio were increased towards full knee extension

Kellis and Katis 2007^a [54]

To investigate the AST H:Q ratio (FR) and the MA H:Q ratio at different velocities and movement directions

17 pubertal males

AST and MA (EMG-moment) H:Q ratio from 0 to 90° of knee flexion at 60°/s and 180°/s

AST H:Q ratio increased as the knee extended and at an increased angular velocity. MA H:Q ratio increased near full extension