Papers of the week (October 2019 – IV)

 In sports science

REACTIVE AND ECCENTRIC STRENGTH CONTRIBUTE TO STIFFNESS REGULATION DURING MAXIMUM VELOCITY SPRINTING IN TEAM SPORT ATHLETES AND HIGHLY TRAINED SPRINTERS

Douglas, J., Pearson, S., Ross, A. & McGuigan, M. (2019). Reactive and eccentric strength contribute to stiffness regulation during maximum velocity sprinting in team sport athletes and highly trained sprinters. J Sports Sci.

  • https://doi.org/10.1080/02640414.2019.1678363

Description

The purpose of this study was to investigate the role of reactive strength, and eccentric strength in stiffness regulation during maximum velocity sprinting in athletes of contrasting sprinting abilities (i.e. team sport athletes compared with highly trained sprinters).

13 team sport athletes and 11 highly trained sprinters were recruited. Vmax was measured using radar, and stiffness regulation was inferred from modelled vertical and leg spring stiffness. Reactive strength (RSI) was determined from a 0.50 m drop jump, and an eccentric back squat was used to assess maximum isoinertial eccentric force.

Sprinter obtained higher Vmax than team athletes (+0.86 m·s−1, ES ±90%), partly due to a briefer contact time (−0.010s, ES: −1.39 ± 0.80) and higher vertical stiffness (+0.15 kN·m·kg−1, ES: 1.74 ± 0.96).

Sprinters exhibited a moderately higher RSI (+0.26, ES: 0.71 ± 0.74) via the attainment of a briefer and more forceful ground contact phase, while RSI also demonstrated large to very large associations with vertical stiffness (r= 0.41) and Vmax (r= 0.72), respectively.

Isoinertial eccentric force was largely correlated with Vmax (0.56), but only moderately correlated with vertical stiffness (r=0.41).

Take Home Messages

  • Improve rate of force development (more force in less time) appears to contribute to the ability to regulate stiffness at maximum velocity.
  • Isoinertial eccentric strength has less impact on Vmax, possibly with greater impact on acceleration and deceleration maneuvers.
  • Strength training program performed by soccer teams should include reactive exercises (i.e., shorter contact time, fast stretch-shortening cycle) as fundamental movements, when coach consider improving the Vmax.

 

A NOVEL HAMSTRING STRAIN INJURY PREVENTION SYSTEM: POST-MATCH STRENGTH TESTING FOR SECONDARY PREVENTION IN FOOTBALL

Wollin, M., Thorborg, K. & Pizzari, T. (2019). A novel hamstring strain injury prevention system: post-match strength testing for secondary prevention in football. Br J Sports Med Month; 1-2.

  • doi: 10.1136/bjsports-2019-100707

Description

The hamstring injury incidence and burden did not decline in male professional football. One-time only preseason screening for hamstring injury risk factors has limited value for preventing hamstring injuries. In fact, since a player’s isometric knee flexion strength may decrease before suffering a hamstring strain (HS) injury, regular hamstring strength monitoring may be valuable. In addition, individualizing post-match recovery processes is key in professional football.

The main of this manuscripts was compared the occurrence and burden of hamstring injury in a cohort where secondary prevention was implemented in addition to standard practice.

Fifty-two players formed the intervention group and undertook regular in-season hamstring strength monitoring. Secondary prevention strategies during the study period included 115 matches that incorporated regular postmatch hamstring strength monitoring with resultant individual player interventions (fig. 1).

The occurrence of HS injury was significantly lower in the intervention group (p=0.003, ES=0.35) compared with control.The HS injury incidence (number of HS injuries/1000-hour exposure) was lower for intervention (0.05/1000 hours) compared with control (0.8/1000 hours) with resultant burdens (time-loss days/1000-hour exposure) of 1.3/1000 versus 14.2/1000 hours of total exposure, respectively.

Take Home Messages

  • Secondary prevention strategy as figure 1 shows can reduce the number and impact of hamstring injuries in male professional development football.
  • Strength impairments greater than the minimal detectable change (14%) of the test since the previous result can be a proper test to an individualized recovery process.
  • Individualization recovery is essential to guarantee success in this process (less occurrence and burden of hamstring injury).
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