Effect of sex on preactivation of the gastrocnemius and hamstring muscles: Table 1

Abstract

Background: The reason for the higher incidence of anterior cruciate ligament injury from non-contact mechanisms in female athletes is not known. Stability of the joint from dynamic restraints occurs through proprioceptive and kinaesthetic mechanisms providing a flexion moment. Reflexive muscle activation is different between the sexes, but it is unclear if sex differences exist in the ability to dynamically stabilise joints through a neuromuscular feed forward process as measured by preactivation of the muscles. Objective: To determine if the level of preactivation of the gastrocnemius and hamstring muscles during dynamic activity is affected by sex. Methods: Thirty four healthy active subjects, evenly grouped by sex, participated in the study. Maximum voluntary contraction normalised electromyographic (EMG) activity of the quadriceps, hamstrings, and gastrocnemius muscles was recorded during downhill walking (0.92 m/s) and running (2.08 m/s) on a 15˚declined treadmill. Preactivation of the EMG signal was calculated by setting a mark 150 milliseconds before foot strike, as indicated by a footswitch. Multiple t tests for sex differences of preactivity mean percentage (M-EMG%) during the downhill activities were performed. Results: The female subjects had a higher M-EMG% for the medial hamstrings than the male subjects (31.73 (9.89) and 23.04 (8.59) respectively; t (2,32) = 2.732, p = 0.01) during walking. No other muscles exhibited a sex difference in M-EMG% during either activity. Conclusion: The female subjects in this study showed higher medial hamstring preactivation. However, this may be because they were not injured, indicating their propensity for joint stabilisation. A long term prospective study is required to eliminate this potential explanation. No sex difference in gastrocnemius preactivation was seen, adding to the controversy about whether this muscle contributes to feed forward joint stability. Further research of preactivation of the musculature of the leg is required.

Altered knee joint neuromuscular control during landing from a jump in 10–15year old children with Generalised Joint Hypermobility. A substudy of the CHAMPS-study Denmark

“…To our knowledge, no studies have evaluated tendon stiffness in GJH. Hypothetically, GM may produce a compensatory force output for the GJH group before landing, and thereby provide stability to the joint and/or resist anterior tibial displacement (Huston and Wojtys, 1996;DeMont and Lephart, 2004). The current higher GM activity was registered before landing, plausibly to compensate for the lower ST activity before landing as part of an anticipatory strategy.…”

Electromyographic preactivation pattern of the gluteus medius during weight-bearing functional tasks in women with and without anterior knee pain

“…EMG activity before the foot contact on the floor) during functional activities were not found. Preparatory and reflexive muscle activation are two neuromuscular processes that contribute to joint stability 21 . The former neuromuscular strategy depends on feedforward motor control of the central nervous system 22 and may have a major function in joint protection 23 .…”

“…The former neuromuscular strategy depends on feedforward motor control of the central nervous system 22 and may have a major function in joint protection 23 . The pre activation of the muscles surrounding a joint may be involved in the control of the position of the limb before a stressful event and also increase the responsiveness of these muscles to provide dynamic stability 21 . Theoretically, both an increased and faster GM preactivation could position the lower limb with an appropriate alignment and prevent hip kinematic alterations, such as excessive hip adduction and internal rotation, and consequently, will avoid excessive patellofemoral stress.…”

Muscle Synergies During a Single-Leg Drop-Landing in Boys and Girls

“…3,5 Among neuromechanical factors that are thought to contribute to ACL injury, muscle activation patterns have been implicated to play a major role because they are responsible for the dynamic control of joint stability during athletic tasks and thus may influence the joint loading environment. Although a number of studies have focused on the role of muscle activation and co-activation patterns during landing in adults, [6][7][8][9][10][11] only a handful of studies have examined sex differences among these patterns in adolescents or pre-adolescents. [12][13][14][15][16][17] It is of practical importance to study differences in muscle activation patterns between boys and girls before puberty so as to provide clues about the onset of the differences observed in adulthood.…”