Ancient origins of horsemanship.

Archaeological evidence of horse domestication dates from 4000 BC in the Eurasian Steppes of the Ukraine. There, Indo-Europeans rode horses and herded them for meat. This had profound social and economic consequences which led to the development of nomadic equestrian cultures. The earliest direct evidence of riding is from Mesopotamian plaques, and correspondence of the Kings of Mari (2000 BC). Indo-Europeans brought the horse to the Near East and there, outside its natural habitat, used specialised knowledge to raise and train horses on a large scale for military use. Hittite instructions on training chariot horses are contained in the Kikkuli text from Anatolia (1350 BC). Systematic conditioning, grain feeding and elements of 'interval training' are notable. Equine prescriptions were also recovered from Ugarit (Syria) which indicate a rational approach to veterinary medicine in the same era. With the evolution of effective training and tools, chariots, metal bits, and the recurve bow, horses became formidable weapons of war. Mounted bowmen succeeded chariots in warfare, particularly nomadic Scythians who dominated Central Asia (1000-500 BC). In the Middle East (Iraq), Assyrians assembled a powerful military empire and employed a vast and skilled cavalry (900-612 BC). The first surviving text on training cavalry mounts is by the Athenian General Xenophon (400 BC) who reveals a sensitive understanding of the horse. Although the horse has been used for herding, transportation and sport, a recurring stimulus for horsemanship throughout history has been its military role.

An energetic basis of equine performance.

Although different physiological and behavioural attributes are needed for various types of equine competition, successful racing depends primarily on the animal's metabolic ability to convert chemical energy to mechanical energy--the function of muscle. Components of these energetic processes include the rate, efficiency and interaction of aerobic and anaerobic metabolism in muscle and the supply and utilisation of fuel. In anaerobic work like racing, fatigue processes may be largely regarded as a function of an intramuscular fuel (phosphogen) depletion, despite the fact that substrates are supplied via the circulation. Physical work capacity in the horse depends then mainly on the rate of aerobic metabolism and the capacity of the anaerobic processes to supply energy for continued muscle contraction. Underlying these processes are physiological limitations of the cardiovascular system and the ultrastructure and biochemistry of muscle. A model is proposed whereby prediction of equine performance is based entirely on parameters of energy metabolism.

Strengthening of human quadriceps muscles by cutaneous electrical stimulation.

The effectiveness of cutaneous electrical stimulation as a muscle-strengthening technique was evaluated by comparison with an isometric regime. Sixteen normal healthy subjects were randomly assigned to either an electrical group or an isometric group. A pretest was given of maximum voluntary force in the quadriceps (extensor) muscles, measured with a cable tensiometer. Subjects then trained (isometrically or by electrical stimulation) four days per week for three weeks. Training by electrical stimulation was via a square-wave pulse (75 Hz and 0.1 ms) with the voltage determined by subject tolerance for ten, 10-sec induced contractions (with 50-sec rest intervals). Isometric training consisted of ten, 10-sec maximal contractions (with 50-sec rest intervals) at each session. Feedback of the generated force was standardised for both groups. Post-training measures were then administered using the same protocol as the pretest. Both groups demonstrated a marked improvement in quadriceps strength of 22 +/- 5.3% for the electrical group and 25 +/- 6.9% increase for the isometric group (p less than 0.02). The change in strength was apparently not dependent on the magnitude of the stimulating voltage (5-10 V) nor on the tension induced. There was no significant difference in the strength gains achieved by the two regimes (p greater than 0.05). No pain, muscle lesions or other ill effects were observed with electrical stimulation. We conclude that cutaneous electrical stimulation is a viable strengthening technique. There are obvious practical applications of this technique to the rehabilitation of patients who are not able to maintain an effective voluntary contraction.

Oxygen deficit and repayment in submaximal exercise.

Oxygen deficit and repayment ratios were investigated at various work loads, intensities and durations. An active baseline was used (walking at 60 m/min) from which deficit and repayment values were calculated. Oxygen uptake (VO2) and core temperatures were measured in 30 males at baseline and during treadmill running (140 m/min) for randomly assigned durations (0.5 ...20 min). Measurements were also made during a 30-min recovery period at baseline work. Results indicated: 1) No difference in O2-repayment between steady-state work and work prior to steady state (P greater than 0.10). 2) O2-repayment was independent of work duration (P greater than 0.10). 3) When workload and intensity were controlled, O2-deficit was not significant factor in O2-repayment (P greater than 0.10). 4) Work intensity (work VO2/VO2 max) was the most significant factor in O2-repayment accounting for 69% of the variance (r equals 0.83, P less than 0.001). Small increments in core temperature and ventilation were not significant factors in O2-repayment. When a working baseline is used, the magnitude of O2-repayment after exercise is independent of the work duration or the attainment of steady state. The extent of O2-repayment after exercise is mainly dependent upon the physiological intensity of the work and the absolute workload (R=0.89, P less than 0.001).

Maximum aerobic power and physical dimensions of children.

Age, height, mass, fat-free mass and vital capacity were used as predictors of maximum aerobic power (VO2 max). The variables were cast in linear form by logarithmic transfomation and submitted to multiple regression analysis. Results indicate VO2 max as a power function of age, height and mass in 50 untrained boys aged 7 to 13 years. In this group the relationship between VO2 max and body mass may be expressed by the equation Y=0.076X0.88 (r=0.92, P <0.01). Age, height and mass together accounted for 89 per cent of the variance in VO2 max (R=0.94, P <0.01). In 30 girl swimmers and in 14 young boys during 22 months of running training, VO2 max was proportional to body mass and indicated greater maximum aerobic power for their size and age. In normally growing children, VO2 max appears to increase more slowly than body mass. Children subjected to aerobic training evidently maintain VO2 max in proportion to their increasing mass throughout adolescence.

Aerobic requirements and maximum aerobic power in treadmill and track running.

Treadmill and track running comparisons were made on eight track athletes. Oxygen uptake (VO2) during steady-state and maximum aerobic power (VO2 max) were measured in a discrete series of three speeds, and at maximal effort. Running speeds were always in sequence from slowest to fastest. Expired air was collected from the runner by the Douglas-bag method, and analyzed by the Lloyd-Haldane technique. Neither VO2 max nor aerobic requirements of running were significantly different in track and treadmill determinations. There were several correlations: 1) VO2 max with body weight (r = .83 P less than .02), 2) treadmill and track determinations of VO2 max (r = .95, P less than .01) and 3) VO2 ml/kg with running velocity m/min (r = .91, P less than .01) where the regression was linear and may be represented by the equation Y = 5.36 + 0.172X, where Syx = 2.7 m102/kg. It is concluded that treadmill determinations of oxygen uptake may be validly applied to track running in calm air within the range of 180...260 m/min.