Physiologic +Gz tolerance responses over successive +Gz exposures in simulated air combat maneuvers.

Introduction: Fighter aircraft pilots are exposed to repetitive headward acceleration (+Gz) during air combat maneuvering. The objective of this study was to compare physiologic responses and the calculated +Gz tolerances of multiple successive +Gz exposures with the responses of the first +Gz exposure.

Methods: There were 13 subjects who performed simulated air combat maneuvering (SACM) profiles composed of 10 rapid-onset rate +Gz cycles with different combinations of short- or long-duration +Gz plateaus (8 or 20 s) and +Gz pauses (1 or 15 s).

Circadian phase delay induced by phototherapeutic devices.

Introduction: The Canadian Forces has initiated a multiple study project to optimize circadian phase changes using appropriately timed phototherapy and/or ingestion of melatonin for those personnel on long-range deployments and shift workers. The work reported here compared four phototherapeutic devices for efficacy in effecting circadian phase delays.

Methods: In a partially counterbalanced treatment order, 14 subjects (7 men and 7 women), ages 18-51 yr, participated in 5 weekly experimental sessions of phototherapy with 4 different phototherapy devices (light tower, light visor, Litebook, LED spectacles) and a no-phototherapy control.

Physical conditioning to enhance +Gz tolerance: issues and current understanding.

Introduction: Although Canadian Forces (CF) efforts directed at developing new G-protection strategies have often raised the question of potential benefits of physical conditioning (PC) on G tolerance (GT), a fatality in a CF fighter aircraft accident, in which it was suggested the pilot may have had 'sub-optimal GT,' sparked renewed interest in this topic.

Methods: A two-part review was conducted: 1) a survey of the literature on the effects of PC on GT; and 2) a determination of further research required to resolve uncertainties on the subject.

Results: Five key themes surfaced: 1) GT as a concept is complex, and has different connotations for different users; 2) the term 'PC' likewise has a variety of meanings, and precise definitions are necessary to compare research results; 3) in examining the relationship between PC and GT, the roles of strength training, muscle fatigue, and aerobic fitness are not as clear as some studies seem to suggest; 4) in designing PC programs to enhance GT, issues such as palatability, efficacy, and intended target population must be addressed for the program to be operationally useful; and 5) there is a requirement for investigations that have controlled important influences such as intercurrent +Gz-stress exposure, proficiency in performing the anti-G straining maneuver, and the wide inter- and intra-individual variation for PC and GT measurements.