RESUMEN
The use of a school backpack is one of the possible causes of back pain in children. Oxygen consumption (VO2), pulmonary ventilation, and heart rate (fc) were measured in 35 pre-pubertal subjects [17 girls and 18 boys, mean (SD) age 11.3 (0.6) years]. They took part in a four-step experiment: (1) standing for 5 min, (2) walking at 3 km.h(-1) for 7 min, (3) walking at 3 km.h(-1) for 7 min carrying a school backpack weighing 8 kg, and (4) walking at 7 km.h(-1) for 5 min with no load. The occurrence of back pain in the last 2-3 years and during the last 15 days was assessed for the subjects by means of a questionnaire. Mean (SD) standing VO2, was 215 (45) ml.min(-1) during walking at 3 km.h(-1), 503 (101) ml.min(-1) during walking without a load, and increased to 541 (98) ml.min(-1) during walking with a load (P<0.01). Carrying a backpack increased fc only minimally. The energy cost of walking at 3 km.h(-1) without the backpack was 10.0 (2.0) ml O2.m(-1), and with the backpack was 10.8 (1.9) ml O2.m(-1) (P< 0.01). The net energy cost of locomotion was 0.129 (0.032) ml.kg body mass(-1).m(-1) for the unloaded condition and slightly lower, at 0.123 (0.025) ml.kg body mass(-1).m(-1) during loaded walking (P < 0.05). Ventilation did not change significantly between unloaded and loaded conditions. When the data were assessed according to the occurrence of back pain, the fc/VO2 slope was significantly lower in children without back pain, even though the net energy cost of locomotion was similar. Overall, these data suggest that the cardiovascular effortrequired for locomotion while carrying a backpack is minimal. However, fatigability and back pain are more likely to take place in less physical performing subjects. Thus, the occurrence of back pain in schoolchildren during locomotion while carrying a backpack may improve with an improvement in their level of fitness.
Asunto(s)
Dolor de Espalda/fisiopatología , Dorso/fisiología , Postura/fisiología , Caminata/fisiología , Dolor de Espalda/etiología , Niño , Fatiga/etiología , Fatiga/fisiopatología , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Italia , Elevación/efectos adversos , Masculino , Consumo de Oxígeno/fisiología , Aptitud Física/fisiología , Ventilación Pulmonar/fisiología , Encuestas y Cuestionarios , Soporte de Peso/fisiologíaRESUMEN
STUDY DESIGN: To study the energy cost of locomotion during ambulation with different orthoses (HIP Guidance Orthosis Orlau Parawalker (PW), n=4; Reciprocating Gait Orthosis (RGO), n=6; RGO + FNS, n=4). OBJECTIVES: Since high energy costs of locomotion have been proposed as a major reason for early rejection of orthotic use, our aims were (a) to evaluate the impact of functional neuromuscular stimulation (FNS) on energy expenditure during orthosis-assisted ambulation; (b) to study whether energy expenditure data can predict the poor long-term patients' compliance and (c) to assess selection criteria for the assignment of the different types of orthosis. SETTING: The study was completed at the Center of Sports Medicine and Center of Bioengineering, don C. Gnocchi Foundation, IRCCS, Milan, Italy. METHODS: The HR/VO2 relationship and the energy cost of locomotion (C) were studied in 14 patients (lesion level C7-T11) during wheelchair (WHCH) use at various speeds and during locomotion with different orthotic devices. Patients' short- and long-term compliance were assessed by questionnaires evaluating duration of and problems related to orthotic use. RESULTS: (a) In patients using RGO + FNS the slope difference of HR/VO2 curves (deltaslHR/VO2) between WHCH and orthosis was significantly lower than in other groups (-3 beats l(-1) in RGO + FNS vs 43 and 52 beats l(-1) in RGO and PW, respectively); (b) neither C, nor VO2 peak, or deltaslHR/VO2 correlated with orthosis duration of use; (c) in the RGO + FNS group, C was lower at maximal walking speed, which linearly correlated with maximal WHCH speed. CONCLUSION: (a) Electrical stimulation seems to improve locomotion, as a consequence of hemodynamic effects, but does not decrease energy expenditure, which remains high; (b) the poor long-term compliance to orthosis use cannot be predicted by the energy expenditure parameters; (c) the subjects who can reach high speeds by WHCH seem to be the most appropriate for RGO + FNS locomotion.