Evolutionary Robotic Approaches in Primate Gait Analysis

Understanding how primates move is particularly challenging because many of the experimentation techniques that would normally be available are unsuitable for ethical and conservation reasons. We therefore need to develop techniques that can maximize the data available from minimally intrusive experimentation. One approach for achieving this is to use evolutionary robotic techniques to build a musculoskeletal simulation and generate movement patterns that optimize some global parameter such as economy or performance, or to match existing kinematic data. If the simulation has a sufficiently high biofidelity and can match experimentally measured performance criteria then we can use it to predict aspects of locomotor mechanics that would otherwise be impossible to measure. This approach is particularly valuable when studying fossil primates because it can be based entirely on morphology and can generate movements spontaneously. A major question in human evolution is the origin of bipedal running and the role of elastic energy storage. By using an evolutionary robotics model of humanoid running we can show that elastic storage is required for efficient, high-performance running. Elasticity allows both energy recovery to minimize total energy cost and also power amplification to allow high performance. The most important elastic energy store on the human hind limb is the Achilles tendon: a feature that is at best weakly expressed among the African great apes. By running simulations both with and without this structure we can demonstrate its importance, and we suggest that identification of the presence or otherwise of this tendon—perhaps by calcaneal morphology or Sharpey’s fibers—is essential for identifying when and where in the fossil record human style running originated.     

Insulin-induced hypoglycemia in fed and fasted exercising rats.

To determine running performance and hormonal and metabolic responses during insulin-induced hypoglycemia, fed and fasted male rats (315 +/- 3 g) were infused with insulin (100 mU/ml, 1.5 ml/h) or saline (1.5 ml/h) for 60 min and then killed at rest or after running on the treadmill (21 m/min, 15% grade). Insulin-infused fed rats ran poorly during the second 10 min of a 20-min exercise test. They were capable of running a total of 43 +/- 5 min, compared with 138 +/- 6 min for saline-infused fed rats. Fasted insulin-infused rats were able to run only 12.8 +/- 0.8 min, compared with 122 +/- 15 min for fasted saline-infused rats. In fasted rats, blood glucose was 1.6 +/- 0.1 mM after 60 min of insulin infusion and 1.2 +/- 0.1 mM after running to exhaustion. Artificial increase of plasma free fatty acids had no effect on performance. Intravenous infusion of glucose at the time of fatigue produced an immediate recovery, allowing the formerly fatigued rats to run 20 min without development of fatigue. These results provide evidence that severe hypoglycemia can be a significant cause of fatigue, even if it occurs early in the course of an exercise bout.     

Case-control study of intrapartum care,cerebral palsy,and perinatal death.

OBJECTIVE--To investigate the relation between suboptimal intrapartum obstetric care and cerebral palsy or death. DESIGN--Case-control study. SETTING--Oxford Regional Health Authority. SUBJECTS--141 babies who subsequently developed cerebral palsy and 62 who died intrapartum or neonatally, 1984-7. All subjects were born at term of singleton pregnancies and had no congenital anomaly. Two controls, matched for place and time of birth, were selected for each index case. MAIN OUTCOME MEASURES--Adverse antenatal factors and suboptimal intrapartum care (by using predefined criteria). RESULTS--Failure to respond to signs of severe fetal distress was more common in cases of cerebral palsy (odds ratio 4.5; 95% confidence interval 2.4 to 8.4) and in cases of death (26.1; 6.2 to 109.7) than among controls. This association persisted even after adjustment for increased incidence of a complicated obstetric history in cases of cerebral palsy. Neonatal encephalopathy is regarded as the best clinical indicator of birth asphyxia; only two thirds (23/33) of the children with cerebral palsy in whom there had been a suboptimal response to fetal distress, however, had evidence of neonatal encephalopathy; these 23 formed 6.8% of all children with cerebral palsy born to residents of the region in the four years studied. CONCLUSION--There is an association between quality of intrapartum care and death. The findings also suggest an association between suboptimal care and cerebral palsy, but this seems to have a role in only a small proportion of all cases of cerebral palsy. The contribution of adverse antenatal factors in the origin of cerebral palsy needs further study.