Influence of shock waves and muscle activity at initial contact on walk-run transition evaluated by two models

Changes in the Preferred Transition Speed With Added Mass to the Foot

This study was conducted to investigate whether adding mass to subjects’ feet affects the preferred transition speed (PTS), and to ascertain whether selected swing phase variables (maximum ankle dorsiflexion angular velocity, angular acceleration, joint moment, and joint power) are determinants of the PTS, based upon four previously established criteria. After the PTS of 24 healthy active male subjects was found, using an incremental protocol in loaded (2 kg mass added to each shoe) and unloaded (shoes only) conditions, subjects walked at three speeds (60%, 80%, and 100% of PTS) and ran at one speed (100% of PTS) on a motor-driven treadmill while relevant data were collected. The PTS of the unloaded condition (2.03 ± 0.12 m/s) was significantly greater (P< .05) than the PTS of the loaded condition (1.94 ± 0.13 m/s). Within both load conditions, all dependent variables increased significantly with walking speed, decreased significantly when gait changed to a run, and were assumed to provide the necessary input to signal a gait transition, fulfilling the requirements of the first three criteria, but only ankle angular velocity reached a critical level before the transition, satisfying all four criteria to be considered a determinant of the PTS.

Methodology of electromyographic analysis of the trunk muscles during walking in healthy subjects: a literature review

PURPOSE

To review and discuss the literature about the use of trunk muscle electromyography - including the use of surface or fine-wire electrodes, site of application and muscle selection - during gait analysis in healthy subjects.

METHODS

The databases Pubmed, Web of Knowledge and Cochrane Library were searched. Articles were included when EMG activity of at least one trunk muscle was measured in healthy subjects during walking.

RESULTS

In the 33 selected articles 491 healthy subjects walked with different velocities on a treadmill and/or overground. The activity of the M. erector spinae, M. multifidus, M. obliquus externus and internus, M. rectus abdominus, M. trapezius, M. latissimus dorsi, M. transversus abdominus, M. iliopsoas and M. quadrates lumborum was measured. Twenty-nine studies used surface electrodes, one study fine-wire electrodes, and the other three studies used a combination. There is no consensus on the exact placement site of the electrodes.

CONCLUSION

Surface electrodes were used more often than fine-wire electrodes and the descriptions of the electrode locations were mostly vague and not consistent among the different studies. There is need for further research to make specific recommendations about the type of electrodes in combination with the optimal locations of application of these electrodes.

Walk-run transition in young and older adults: with special reference to the cardio-respiratory responses

Cardio-respiratory responses of young and older subjects performing walking and running protocols at the walk-run transition speed (WRT) were compared. A total of 26 volunteers assigned to younger (YG, 24 +/- 3 years) and older (OG, 64 +/- 6 years) groups underwent a protocol to determine the WRT used in 6-min walking and running protocols. Oxygen uptake (VO(2)), ventilation (V (E)), expired carbon dioxide (VCO(2)), heart rate (HR) and perceived exertion (RPE) were assessed. Oxygen pulse (O(2) pulse) and respiratory exchange ratio (RER) were calculated. The WRT was not different between groups (OG: 6.84 +/- 0.69 km h(-1) vs. YG: 7.04 +/- 0.77 km h(-1), P = 0.62). No between-group differences were found within a given gait pattern for VO(2) (P = 0.061) and VCO(2) (P = 0.076). However, VO(2) (P = 0.0022) and VCO(2) (P = 0.0041) increased in OG when running, remaining stable in YG (VO(2): P = 0.622; VCO(2): P = 0.412). The VE was higher in OG compared to YG in walking (P = 0.030) and running (P = 0.004) protocols. No age-related (P = 0.180) or locomotion (P = 0.407) effects were found for RER. The HR increased in OG and between-group difference was detected while running (P = 0.003). No within- (P = 0.447) or between-group (P = 0.851) difference was found for O(2) pulse. The net VO(2) increased from walking to running in OG (P < 0.0001) but not in YG (P = 0.53), while RPE was lower in YG (P = 0.041) but stable in OG (P = 0.654). In conclusion, the WRT speed was similar across the age groups. However, the VO(2) and VCO(2) increase from walking to running was larger for OG than YG. The HR, VE and RPE were also higher when running in OG compared to YG. Therefore, the locomotion strategy had different impacts on the metabolic demand of older and younger subjects.