Biomechanical Characteristics of the Knee Joint During Single-Leg Landing of Soldiers and its Relationship with Isokinetic Muscle Strength / 医用生物力学

Objective To analyze the impact of soldiers’ single-leg landing with load carriage on knee joint, and investigate its relationship with muscle strength, so as to provide references for daily load carriage training. Methods A total of 12 soldiers were required to perform single-leg landing from the 30 cm height without load carriage and with 15 kg load carriage,respectively.The kinematic and kinetic parameters were collected using Vicon motion capture system and AMTI force platform. The surface electromyography (sEMG) of anterior and posterior thigh muscles were also collected simultaneously, and the isokinetic strength during knee flexion and extension was tested. Results Compared with landing without load carriage, knee flexion angle and joint reaction force significantly increased during landing with 15 kg load carriage (P0.05). There was a significant negative correlation between peak moment of knee extension and vertical ground reaction force during single-leg landing without load carriage (P0.05). Conclusions Knee flexion angle and joint reaction force significantly increase during single-leg landing with 15 kg load carriage, the activation of anterior and posterior thigh muscles can relieved the ground reaction force during landing, and muscle strength plays some role in preventing landing injury.

Influence of Load Carriage during Military Walking on Lower Limb Gait Characteristics / 医用生物力学

Objective To evaluate the influence of different load carriages during military walking on the gait of lower limbs. Methods In a randomized cross-over design, 15 healthy young males were asked to perform self-paced walking with a normal uniform under a load carriage of 0 kg, 7.5 kg, 27 kg, and 50 kg for four times. The kinematics parameters of the pelvis, knee, and ankle were evaluated by the Vicon motion capture system and AMTI force plates. Results With increasing load carriage, the stride frequency relatively improved, whereas the stride reduced and the speed was maintained on the whole. The peak left/right hip flexion and extension angle and peak knee adduction angle were obviously affected by the load carriage, whereas the movement magnitudes could be maintained. The peak varus angle of the left ankle and peak valgus angle of the right ankle were also affected. The peak force and moment of the left/right knee and ankle increased. Conclusions With increasing load carriage, overall, the movement magnitudes of lower limb joints were maintained under the given loads, whereas the lower limb loads were increased, which could increase the potential risk of lower limb injuries.

Effect of lower-limb dominance and non-dominance shuttle runs under load carriage on the balance responses in young cadets / 中国应用生理学杂志

OBJECTIVE@#This test was designed to evaluate the effect of lower-limb dominance and non-dominance shuttle runs under load carriage during different exercise load at the same exercise intensity on the balance responses.@*METHODS@#Ten healthy young males were joined in this experiment, they were (20.80±2.04) years old and (173.99±2.87) cm tall. In a randomized cross-over design, they performed four times shuttle runs under unilateral load carriage:20 m×5 at dominant side, 20 m×5 at non-dominant side, 20 m×10 at dominant side, 20 m×10 at non-dominant side respectively. Balance abilities were evaluated immediately and 20 minute post-exercise respectively, and R-R interval was recorded.@*RESULTS@#The HR, EPOC and TRIMP for all exercise load were increased significantly after shuttle runs compared to rest (0.05), which showed symmetrical change. In addition, during 20 minute recovery, the balance ability for all exercise load was returned to the rest value (>0.05).@*CONCLUSIONS@#The shuttle runs could impair the trunk control ability immediately post-exercise, the magnitude of mediolateral movement was increased as the exercise load increased. The changes of balance responses were similar between the dominant and the non-dominant side, the dominant and the non-dominant side might show cross-effects.

Cardiorespiratory changes with compact backpack system and distributed mode of load carriage.

In Indian Army, soldiers normally carry 21.4 kg in backpack (BP), haversack, and web distributed in different parts of the body and rifle in hand. This load distribution is unequal, may involve excess energy expenditure, mostly uncomfortable, and restricts the normal movement of the hand carrying rifle. A new BP has been developed which accommodates the rifle on sides leaving the hands free. Physiological evaluation of load carriage [21.4 kg in the existing Load Carriage ensembles (LCe) and in the new BP] and without load was carried out on a group of Indian Army soldiers (n= 8) to understand the efficacy of the new BP vis-á-vis the existing one at 4.5 km/h speed at level ground and at 5% gradient on a treadmill in controlled laboratory environment. Heart rate, oxygen consumption, relative work load and energy expenditure were determined and one-way repeated measure ANOVA was applied to compare the results. All the physiological parameters showed higher responses in distributed mode in comparison to compact mode. However, the differences were not significant. The study may be carried out on a larger sample size to find out the better efficacy of compact mode of load carriage over the distributed mode.

A influência de duas mochilas sobre a cinemática da coluna de crianças / The influence of two backpack loads

This study aimed to analyze the effect of backpack load carriage over the spine. The studies that have investigated load carriage using backpacks have analyzed the lower limb dynamics and have not focused on the spine. In addition, the strategies applied by children may differ from adults as the relative weight differs between adolescents and adults. Methods: Ten schoolboys (13.9 ± 0.6 years-old; 1.53 ± 0.05 m; 44.9 ± 3.3 kg) volunteered to participate after their parents sign an informed consent form. Participants walked in a treadmill during approximately 15 minutes carrying a specially built backpack with a load that corresponded to 0.10 and 20 percent BW. A number of landmarks were placed over the subjects back and allowed reconstruction of the spinal profiles in the sagittal and frontal planes. The relation between the segments formed between acromium markers and the posterior superior iliac crest markers was used as a spinal rotation index. The maximum, minimal, mean and range of motion of the thoracic and lumbar regions and the whole spine were analyzed. The gait cycle was applied to normalize the gait cycle. Results indicated differences between the two loads (10 percent) BW and 20 percent BW. A number of changes in the spinal kinematics was found. In the saggital plane the range of movement was unaltered, although there was an increased in the flexion, which was interpreted as a compensatory strategy to counteract the effect of the load. These results are in line with the idea that the use of a backpack increases anterior leaning of the trunk, but are in disagreement with the notion that pronounced changes in the range of motion occur. Carrying a backpack did not produce a clear effect over the variables selected to identify thoracic and lumbar spine regions in the sagittal plane. Conclusion: Carrying a load that corresponded to 20 percent BW influences spinal kinematics in all planes of movements. These changes may impose an important change in posture and stress applied over the posterior aspect of the vertebral column. The slow walking speed used in the present study may have not induced large changes in the kinematics of the vertebral column as in other studies in which walking was performed in greater speeds. Thus, it is suggested that weight of the backpack is not the only factor that determines the movements of the vertebral column.

Este estudo visou analisar o efeito do carregamento de cargas por meio de mochilas sobre a coluna. Os estudos que investigaram o carregamento de cargas utilizando mochilas têm analisado a dinâmica de membros inferiores e não tem focado a coluna vertebral. Em adição, as estratégias aplicadas por crianças podem diferir visto que as cargas relativas podem diferir entre adolescentes e adultos. Métodos: dez escolares (13,9 ± 0,6 anos; 1,53 ± 0,05 m; 44,9 ± 3,3 kg) foram voluntários para participar do estudo após seus pais consentirem e assinarem um formulário livre e esclarecido. Os participantes caminharam em uma esteira. Durante aproximadamente 15 minutos carregando uma mochila especialmente feita que correspondia a 0,10 e 20 por cento do peso corporal. Um número de marcas corporais foi colocada nas costas dos sujeitos que permitiram a reconstrução dos perfis da coluna nos planos sagital e frontal. A relação entre os segmentos formados pelas marcas entre os acrômios e as cristas ilíacas foi usada como um índice de rotação da coluna. Os valores máximos, mínimos, médios e as amplitudes de movimento das regiões torácica e lombar e a coluna toda foram analisados. O ciclo da marcha foi normalizado pelo contato sucessivo de dois contatos do calcanhar com o solo. Resultados indicaram diferenças entre as cargas (10 e 20 por cento) PC). Um número de mudanças na cinemática da coluna foi encontrada. No plano sagital a amplitude de movimento permaneceu inalterada, todavia, houve um aumento na flexão a qual foi interpretada como uma estratégia compensatória em resposta ao efeito da carga. Os resultados estão em linha com a idéia que o uso de mochilas aumenta a inclinação anterior do tronco, mas em discordância com a noção que pronunciadas mudanças na amplitude de movimento ocorrem. O carregamento de cargas não produz um efeito claro sobre as variáveis selecionadas para identificar as alterações nas regiões lombar e torácica no plano sagital. Conclusão: o carregamento de cargas que correspondem a 20 por cento PC influenciam a cinemática da coluna em todos os planos de movimento. Essas mudanças podem impor importantes mudanças sobre a postura e o estresse aplicado sobre os aspectos anteriores e posteriores da coluna vertebral. A baixa velocidade de deslocamento usada no presente estudo podem não ter induzido grandes mudanças na cinematica da coluna vertebral, como demonstrado em outros estudos que usaram maiores velocidades de deslocamento. Desta forma, sugere-se que o peso da mochila não é o único ator que determina os movimentos da coluna vertebral.