Lowering minimum eye height to increase peak knee and hip flexion during landing

The purpose was to determine the effect of lowering minimum eye height through an externally focused object on knee and hip flexion and impact forces during jump-landing. Kinematics and ground reaction forces were collected when 20 male and 19 female participants performed jump-landing trials with their natural minimum eye height, and trials focusing on lowering their minimum eye height to an external object, which was set at 5% or 10% of standing height lower. Participants demonstrated decreased minimum eye height and increased peak knee and hip flexion during early-landing and stance phase when focusing on lowering eye height to the external object (p \u3c 0.01). Peak vertical ground reaction forces during early-landing also decreased for the greater force group (p \u3c 0.001). Jump-landing training through manipulating eye height provides a strategy that involves an external focus and intrinsic feedback, which may have advantages in promoting learning and practical application

Kinematic Analyses of Parkour Landings From as High as 2.7 Meters

During landing tasks, forces and moments are generated by the musculoskeletal system at surface contact to progressively decelerate the velocity of the body (Dufek and Bates, 1990; McNitt-Gray, 1993). When landing after a forward jump, the body’s downward velocity must be decelerated by an upward acceleration, while its forward velocity needs to be decelerated by a backward acceleration. Inappropriate landing patterns can cause excessive loading to the body, resulting in musculoskeletal injuries. The anterior cruciate ligament is commonly injured by abnormal landing patterns during athletic activities (Dai et al., 2015b; Krosshaug et al., 2007). Military training also involves jump-landing tasks such as parachuting, jumping off a vehicle, and traversing a ditch; all which increase exposure to jump-landing associated injury risk (Ekeland, 1997; Owens et al., 2007; Sell et al., 2010). Developing safe and effective landing strategies has implications for both injury prevention and performance training. Investigators have examined the effects of landing heights, distances, and techniques on performers’ motion, impact forces, and their associated risk of injury (Dai et al., 2015a; Dufek and Bates, 1990; McNitt-Gray, 1993). Lower extremity loading increases when the landing height and distance are increased (Dufek and Bates, 1990; McNitt-Gray, 1993; Zhang et al., 2000). Potential strategies to decrease lower extremity loading include landing on the forefoot, increasing knee and hip joint range of motion, and lengthening landing time (Dai et al., 2015a; Devita and Skelly, 1992; Zhang et al., 2000). However, previous findings are based on landing heights less than 1.5 m in combination with traditional landing techniques. An increased landing velocity resulting from a high landing height does not necessarily result in injury if appropriate landing techniques are utilized. As an example, Parkour is a form of acrobatic street gymnastics that has gained public popularity in the last decade (Puddle and Maulder, 2013). One important skill in Parkour is to land safely from high heights (\u3e1.5 m) such as vertical walls. Novel landing techniques with the use of hands and rolling motions have been utilized by Parkour practitioners. Investigators have quantified the effect of Parkour precision and roll landings on landing forces from a landing height of 0.75 m (Puddle and Maulder, 2013). The biomechanics of how Parkour practitioners land from higher heights remains unclear. Therefore, the purpose of this study was to quantify the landing kinematics of Parkour practitioners landing from 0.9, 1.8, and 2.7 m utilizing the squat, forward, roll, and stiff landing techniques. It was hypothesized that the stiff landing would exhibit the least landing time and greatest change in vertical velocity during the early landing, while the roll landing would demonstrate the greatest landing time and least changes in vertical and horizontal velocities during the early landing for all landing heights. In addition, it was hypothesized that the four landing techniques would exhibit different lower extremity kinematics

Effect of External Loading on Force and Power Production During Plyometric Push-Ups

One common exercise to train upper-body strength and power is the push-up. Training at the loads that would produce the greatest power is an effective way to increase peak power. The purpose of the current study was to quantify the changes in peak force, peak power, and peak velocity among a modified plyometric push-up and plyometric push-ups with or without external loading in physically active young adults. Eighteen male and 17 female participants completed 4 push-ups: (a) modified plyometric push-up on the knees, (b) plyometric push-up without external loading, (c) plyometric push-up with an external load of 5% of body weight, and (d) plyometric push-up with an external load of 10% of body weight. Two force platforms were set up to collect vertical ground reaction forces at the hands and feet. The modified plyometric push-up demonstrated the lowest force, power, and velocity (5.4≥ Cohen\u27s dz ≥1.2). Peak force and force at peak velocity increased (3.8≥ Cohen\u27s dz ≥0.3) and peak velocity and velocity at peak power decreased (1.4≥ Cohen\u27s dz ≥0.8) for the push-up without external loading compared with the 2 push-ups with external loading. No significant differences were observed for peak power among the push-ups with or without external loading (0.4≥ Cohen\u27s dz ≥0.1). Although peak power is similar with or without external loading, push-ups without external loading may be more beneficial for a quick movement, and push-ups with external loading may be more beneficial for a greater force production