Evaluation of Efficiencies Among Climbing Systems and Rope Diameters
Evaluation of Efficiencies Among Climbing Systems and Rope Diameters
John Ball, South Dakota State University
Climbing is a high-risk activity associated with severe non-fatal and fatal injuries. While the primary causal agent for a climbing incident may be anchor failure or contact with an energized conductor, an underlying factor may be fatigue due to inefficiencies in a climber’s ascending and work-positioning techniques. Fatigue has been cited as a factor in OSHA investigation summaries for climbing incidents.
Efficiency is economy of motion. More efficiency means the worker is expending less energy to accomplish a task such as climbing. An efficient climber is not operating at maximum capacity so their performance can be prolonged and fatigue reduced. This is an important consideration for climbers as they may be aloft a significant period of the workday.
This study will evaluate common tree-climbing systems, both moving-rope systems (MRS) and stationary-rope systems (SRS) and measure the efficiency and economy of tactics through the relationship between oxygen consumptions (VO2) and heart rate (HR) to determine the most efficient approaches. The VO2 for measuring aerobic power is ml of oxygen consumed per kg of body weight of the worker per minute (ml//kg/min). Oxygen consumption is measured with a portable metabolic analyzer connected to a mask that covers the nose and mouth. Wearing a mask does not affect performance or increase risk to the climber. There are no cables, hoses, or packs to catch or hinder performance. These are routinely used in climber studies set in outdoor environments. The ascent and climbing routes for this study will be set where there are no branches to interfere with the climbs. In addition to VO2, the worker’s heart rate (HR) is also an important measure, and this will also be monitored through sensors that are placed under the shirt.
In the last few years, smaller diameter ropes have been gaining in popularity. The climbing systems have not changed during this period and climbers are still using the ropes the same ways. It is hypothesized that the smaller diameter ropes may be causing climber to exert greater hand force during climbing. This may impact fatigue and are to be assessed as part of this study.
To assess local force demands and postural demands on the upper extremities during tree climbing activities, the subject/climber will have EMG electrodes attached to the forearm to record grip force with two different glove configurations.
Study Results
A key outcome for this project was the development of a methodology for testing efficiency of climbing methods and climbing aid. New climbing methods and aids are being developed and introduced to climbers at an increasing rate, yet the profession does not have a way of quantifying their efficiencies. The methodology, patterned after what has been used in sport climbing, will help researchers standardize methods for future arborist performance studies.
The results of the first phase of this research show differences in heart rate and oxygen consumption among the four climbing methods. The heart rate more than doubled during the ascend regardless of the use of a moving or stationary rope system. Heart rate increased during climbing, in part, to arm positioning. The heart must work faster to move blood against gravity when the arms reach up above the shoulders and pull. Keeping the arms below the shoulders and using them more for balance then pulling maintains a lower heart rate during a climb. Climbs using SRS and foot ascenders resulted in the lowest heart rates, in the 100s and 110s, while the body thrust was in the 160s.
The VO2 rate, measured in ml of oxygen/kg of body weight/minute, also increased during ascents. Oxygen consumption did not vary as much among climbing systems and techniques as it did for heart rate. The VO2 rate at rest was about three or four ml/kg/min for the climbers but averaged in the 20s or 30s during the climb for all techniques. The SRS technique using the foot and foot loop ascenders had lowest average VO2, with some climbers in the lower twenties compared to the mid to upper twenties for the other climbing methods. The VO2 peaks were in the 30s, with some climbers peaking at 39 ml/kg/min. There was a difference in VO2 peaks among the techniques with climbers using the SRS stationary line and foot and foot loop ascenders remaining in the twenties.
Aerobic fitness is key for climbers. The oxygen demands of climbing requires good lung capacity to consume oxygen and a strong heart to move the oxygenated blood. Cardio-respiratory exercises such as cycling or running are appropriate training for climbers. Strength training is also important, both for upper and lower body.
Year of Grant Awarded: 2022
Grant Program: Safe Arborists Techniques Fund Grant Program
Grant Title: Evaluation of Efficiencies Among Climbing Systems and Rope Diameters
Researcher: John Ball