R) were measured for DROM. Participants performed drop landings onto a force platform at two vertical descent velocities (2.25 ± 0.15 and 3.21 ± 0.17 m·s−1), while EMG activity of four shank muscles and three-dimensional ankle joint kinematics were recorded. Participants were classified into low (37.7° ± 2.5°) and high (48.4° ± 2.5°) DROM groups. Results: Ground reaction force, EMG, dorsiflexion angle, plantarflexion moment, and Achilles tendon force outcome variables were all equivalent for the two DROM groups during each landing condition. However, the low DROM group performed each landing condition at a significantly greater percentage of their DROM and displayed significantly more ankle eversion throughout most of the movement. The low and high DROM groups displayed DROM percentages of 27 ± 11 and 10 ± 11 (P = 0.013), 32 ± 9 and 23 ± 9 (P = 0.056), 60 ± 13 and 46 ± 13 (P = 0.004), and 66 ± 16 and 54 ± 9 (P = 0.003) when they encountered the peak plantarflexion moments, Achilles tendon force, eversion angles, and dorsiflexion angles, respectively. Conclusion: Participants with a low DROM absorbed the landing impact forces with their plantarflexor muscle-tendon units in a more lengthened and everted position. Athletes with a low DROM may be more likely to regularly overload their plantarflexor muscle-tendon units, thereby potentially exposing themselves to a higher likelihood of incurring injuries such as Achilles tendinopathy....

Kicking strikes are fundamental in combat sports such as Taekwondo, karate, kickboxing, Muay Thai, and mixed martial arts. This review aimed to explore the measurement methods, kinematics such as velocities, kinetics such as impact force, determinants, and injury potential of kicking strikes in combat sports. Searches of Academic Search Premier, The Allied and Complementary Medicine Database, CINAHL Plus, MEDLINE, SPORTDiscus, Scopus, and Web of Science databases were conducted for studies that measured kicking velocity and impact force. A total of 88 studies were included in the review. Studies most frequently involved only male participants (49%) aged between 18 and 30 years of age (68%). Studies measuring velocity predominantly implemented camera-based motion capture systems (96%), whereas studies measuring impact force displayed considerable heterogeneity in their measurement methods. Five primary strikes were identified for which foot velocities ranged from 5.2 to 18.3 m/s and mean impact force ranged from 122.6 to 9015 N. Among the techniques analysed, the roundhouse kick exhibited the highest kicking velocity at 18.3 m/s, whilst the side kick produced the highest impact force at 9015 N. Diverse investigation methodologies contributed to a wide value range for kicking velocities and impact forces being reported, making direct comparisons difficult. Kicking strikes can be categorised into throw-style or push-style kicks, which modulate impact through different mechanisms. Kicking velocity and impact force are determined by several factors, including technical proficiency, lower body strength and flexibility, effective mass, and target factors. The impact force generated by kicking strikes is sufficient to cause injury, including fracture. Protective equipment can partially attenuate these forces, although more research is required in this area. Athletes and coaches are advised to carefully consider the properties and potential limitations of measurement devices used to assess impact force.

K squat using three-dimensional motion analysis and ground reaction force data. Nine male participants (mean age = 26.4 ± 5.4 years, height = 1.79 ± 0.08 m, and mass = 84.7 ± 16.1 kg) completed 2 experimental testing sessions wearing 2 different forms of training footwear: (a) standard sports trainers (running shoes [RS]) and (b) specialized weightlifting shoes (WS). On each test day, participants completed a sequence of 5, 3, and 1 repetitions of a barbell back squat using 50, 70, and 90%, respectively, of their 1 repetition maximum (1RM) load in each of the shoe conditions. Shoe order, which was initially randomly assigned for test day 1, was reversed on test day 2. Significant main effects were found for peak dorsiflexion of both left (p < 0.001) and right (p < 0.001) ankles. Pairwise post hoc comparisons showed that the RS condition exhibited significantly more dorsiflexion compared with the WS condition in both left and right ankles. There was also a significant main effect of load (%1RM) within the left ankle (p < 0.01) with post hoc comparisons showing that there was a significant increase in peak dorsiflexion angle from 50 to 90% (p ≤ 0.05) and 70–90% of 1RM (p ≤ 0.05) but no difference between 50 and 70% of 1RM (p = 1.000). These findings indicate that further investigation is necessary to substantiate claims regarding the benefits of wearing WS during resistance training exercises targeting the squat movement....

Whitting JW, Steele JR, Jaffrey MA, Munro BJ. Parachute landing fall characteristics at three realistic vertical descent velocities. Aviat Space Environ Med 2007; 78:1135–42. Introduction: Although parachute landing injuries are thought to be due in part to a lack of exposure of trainees to realistic descent velocities during parachute landing fall (PLF) training, no research has systematically investigated whether PLF technique is affected by different vertical descent conditions, with standardized and realistic conditions of horizontal drift. This study was designed to determine the effects of variations in vertical descent velocity on PLF technique. Methods: Kinematic, ground reaction force, and electromyographic data were collected and analyzed for 20 paratroopers while they performed parachute landings, using a custom-designed monorail apparatus, with a constant horizontal drift velocity (2.3 m · s⁻¹) and at three realistic vertical descent velocities: slow (2.1 m · s⁻¹), medium (3.3 m · s⁻¹), and fast (4.6 m · s⁻¹). Results: Most biomechanical variables characterizing PLF technique were significantly affected by descent velocity. For example, at the fast velocity, the subjects impacted the ground with 123° of plantar flexion and generated ground reaction forces averaging 13.7 times body weight, compared to 106° and 6.1 body weight, respectively, at the slow velocity. Furthermore, the subjects activated their antigravity extensor muscles earlier during the fast velocity condition to eccentrically control the impact absorption. Discussion: As vertical descent rates increased, the paratroopers displayed a significantly different strategy when performing the PLF. It is therefore recommended that PLF training programs include ground training activities with realistic vertical descent velocities to better prepare trainees to withstand the impact forces associated with initial aerial descents onto the Drop Zone and, ultimately, minimize the potential for injury.

The Australian Defence Force Parachute Training School instructs trainees to make initial ground contact using a flat foot whereas United States paratroopers are taught to contact the ground with the ball of the foot first. This study aimed to determine whether differences in foot pitch affected parachute landing technique. Kinematic, ground reaction force and electromyographic data were analyzed for 28 parachutists who performed parachute landings (vertical descent velocity = 3.4 m x s(-1)) from a monorail apparatus. Independent t-tests were used to determine significant (p < 0.05) differences between variables characterizing foot pitch. Subjects who landed flat-footed displayed less knee and ankle flexion, sustained higher peak ground reaction forces, and took less time to reach peak force than those who landed on the balls of their feet. Although forefoot landings lowered ground reaction forces compared to landing flat-footed, further research is required to confirm whether this is a safer parachute landing strategy.