DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary

NIOSH evaluated reinforcing 

ironworkers’ (rodbusters) exposures to risk factors for developing low-back and hand 

disorders when tying together reinforcing steel bars (rebar) on a freeway bridge. Rodbusters used three techniques 

to tie rebar together—a pliers 

and a tie wire wheel, a battery 

operated power tier (PT), and 

a PT with an extension handle 

(PTE). NIOSH found that using the PT and PTE reduced 

the rodbusters’ exposures to risk 

factors for work-related low-back 

and hand-wrist disorders. In addition, power tying was twice 

as fast as than pliers tying.

Reducing Work-Related Musculoskeletal 

Disorders among Rodbusters 

Description of

Exposure

Reinforcing ironworkers have reported high prevalence rates for workrelated musculoskeletal disorders 

(WMSD) symptoms affecting the 

low–back (80.2%) and wrists/hands 

(48.4%) [Cook et al 1996]. Boston-area rodbusters reported high 

prevalence rates for self-reported 

symptoms of the low-back (52.2%) 

and hands/wrists/fingers (47.8%) and 

high prevalence rates of doctor-diagnosed WMSDs, including ruptured 

spinal discs (14%) and carpal tunnel 

syndrome (16%) [Forde et al. 2005]. 

Traditionally, pliers and a tie wire

wheel have been used to pull, wrap, 

twist, and cut the ‘tie’ wire around 

two or more concrete reinforcing 

bars. This requires using both hands 

and making rapid and repetitive 

hand, wrist, and forearm movements 

while gripping the pliers. In recent 

years, power tiers have become available. The PT is a battery-powered 

and trigger-operated wire tier that 

automatically wraps, cuts, and ties 

the wire around the rebar. Tying rebar at ground level using either the 

pliers or the PT requires working in a 

stooped posture. A height-adjustable 

extension handle (PTE) is commercially available for one type of handheld PT enabling the worker to tie 

the rebar while standing. 

Evaluation

A concrete reinforcing contractor requested that NIOSH evaluate workers’ exposures to WMSD risk factors 

during rebar tying on a freeway bridge 

deck construction project that required making more than 2 million “ties.” The contractor’s workers 

used both pliers and PTs to tie rebar. NIOSH introduced the PTE as a 

third technique to be investigated in 

the study. Although rodbusters perform other job activities that require 

“maximum muscle force to lift, 

push, pull, or carry objects” [ONET 

2008], NIOSH analyzed only rebar 

tying during this study because of 

the nature of the request and time 

constraints.

The three rebar tying methods were 

studied with relation to (1) hand, wrist, 

and forearm position and movements 

and (2) trunk (or back) position. 

Results

Hand/Wrist

•	 Pliers tying involved the most 

hand, wrist, and forearm motions 

and the highest risk for developing 

a WMSD of the hand-wrist (see 

Figure 1). 

•	 PT and PTE tying involved fewer hand, wrist, and forearm motions and less risk for developing a 

WMSD of the hand-wrist. 
•	 Workers rated hand-wrist effort highest for pliers and 

the PTE, and least for PT tying. 

Low-back

•	 Pliers tying at ground level involved the most risk for 

low-back problems.

•	 PT tying at ground-level allowed workers to support 

the weight of their trunk with one hand.

•	 PTE tying could be done standing-up with the least 

strain on the low-back. 

•	 Workers said they had the most low-back discomfort 

using pliers and the least using the PTE and the PT. 

NIOSH found that the frequency and duration of the 

hand and wrist motions are associated with increased 

risk of a hand-wrist WMSDs [NIOSH 2005]. The similar effort ratings for tying with pliers and the PTE conflict with the results of other studies in which workers 

having experience using the extension handle reported 

much less effort [Vi 2003]. Workers did not have time to 

use the extension handle before this study began. Consequently, workers were observed holding the PTE far 

from the body, which would increase the stress on the 

shoulder, elbow, and wrist.

Workers reported less low-back effort using the PT than 

the pliers, although both required frequent and prolonged 

stooping (see Figure 2). During the study, NIOSH observed all workers using the free hand/arm—the one not 

holding the PT—to support their body when stooping. 

This posture likely reduced the stress to the low back 

and the report of less low-back effort, which is consistent with other reports [Gallagher et al 1988; Ferguson 

2002; Kingma 2004].

Tying rebar using the PT and PTE was faster than using the pliers. Workers were able to complete twice as 

many ties during the study period with the PT as compared with the pliers. Vi [2005] reported that PTE tying 

by experienced workers was twice as fast as pliers tying. 

Contractors and workers have reported difficulties with 

power tier use that can affect actual productivity levels, 

including tool malfunction, wire jams, and short battery 

life [ ORISE 2007]. Power tiers can make one type of tie 

and are not appropriate for all applications.

Recommendations

Contractors and workers should take the following steps 

to reduce the risk of developing MSDs when tying rebar on freeway bridge decks and other construction 

Figure 1. Rebar tying using pliers. Note the bent posture and awkward hand position.

Figure 2. Rebar tying using a MAX–USA RB–392 power 

tool. Note the bent posture.
projects requiring frequent and prolonged rebar tying. 

[Albers and Hudock 2007; NIOSH 2005]: 

•	 Use PTs instead of pliers to reduce harmful hand-wrist 

movements.

•	 Use a PTE when tying ground level rebar.

•	 When using a PTE, hold it close to the body to avoid 

unnecessary stress and strain on the wrist, arm, and 

shoulder (see Figure 3).

•	 When using a PTE extension, adjust the height of the 

hand-grip so that it can be firmly held with your arm 

hanging relaxed to minimize stress on the upper extremities and low back.

•	 Report low-back or upper-limb aches, stiffness, or pain that 

may be due to your work to your health care provider.

Acknowledgments

This document was prepared by Jim Albers, MPH, CIH 

and Stephen D. Hudock, Ph.D., CSP, Division of Applied Research and Technology, National Institute for 

Occupational Safety and Health.

References

Albers JT, Hudock SD [2007]. Biomechanical assessment of three rebar tying techniques. Int J Occup Safety Ergonomics 13(3):227–237.

Cook TM, Rosecrance JC, Zimmerman CL [1996]. The 

University of Iowa construction survey. Washington, 

DC: Center to Protect Workers’ Rights, Report No. 

E1–96. 

Forde MS, Punnett L, Wegman DH [2005]. Prevalence 

of musculoskeletal disorders in union ironworkers. J 

Occup Environ Hygiene 2:203–212.

Ferguson FA, Gaudes-MacClaren LL, Marras WS, Waters, 

TA, Davis KG [2002]. Spinal loading when lifting from 

industrial storage bins. Ergonomics 45(6):399–414.

Forde M, Buchholz B [2004]. Task content and physical 

ergonomic risk factors in construction ironwork. Int J 

Ind Ergon 34:319–333.

Gallagher S, Marras WS, Bobick TG. [1988] Lifting in 

stooped and kneeling postures: effects on lifting capacity, metabolic costs, and electromyography of eight 

trunk muscles. Int J Ind Ergonomics 3(1):65–76.

Kingma I, van Dieen JH [2004]. Kingma Lifting Lifting over an obsta over an obstacle: effects of one-handed lifting and hand support on 

trunk kinematics and low back loading. J Biomechanics 37:249–255.

NIOSH [2005]. NIOSH Health Hazard Evaluation Report: Genesis Steel Services, Inc., Baltimore, MD. Cincinnati, OH: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, 

National Institute for Occupational Safety and Health, 

NIOSH HHE Report 2003–0146–2976 [www.cdc.

gov/niosh/hhe/reports/pdfs/2003-0146-2976.pdf]. 

ONET [2008]. Reinforcing iron and rebar workers (47–

2171.00). Occupational Information Network (O*NET) 

Online http://online.onetcenter.org/link/summary/ 

47-2171.00. Accessed April 17, 2008.

ORISE [2007]. Message testing and formative research 

on perceived stakeholder barriers and incentives for 

the adoption and diffusion of concrete reinforcement 

and placement interventions: focus group report. Oak 

Ridge, TN: Oak Ridge Institute for Science and Education.

Vi P [2003]. Reducing risk of musculoskeletal disorders 

through the use of rebar-tying machines. Appl Occup 

Environ Hygiene 18(9):649–654.

Figure 3. Rebar tying using a MAX–USA RB–392 power 

tool with adjustable extension.
DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Official Business

Penalty for Private Use $300

For More Information

More information about ergonomics in construction is available from the NIOSH publication 

NIOSH [2007]. Simple solutions: ergonomics for construction workers. By Albers J and Estill C. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 

2007–122 [http://www.cdc.gov/niosh/docs/2007-122/]. 

For general information about construction safety and health 

topics, visit the NIOSH Construction Topic Page at http://

www.cdc.gov/niosh/topics/construction.

For general information about musculoskeletal disorders and 

carpal tunnel syndrome, visit this NIOSH Topic Page: http://

www.cdc.gov/niosh/topics/ergonomics/

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NIOSH is the Federal agency responsible for conducting research and making recommendations to prevent work-related illness and injuries. All Workplace Solutions are based on 

research studies that show how worker exposures to hazardous agents or activities can be significantly reduced.

Reducing Work-Related Musculoskeletal

Disorders among Rodbusters 

DHHS (NIOSH) Publication No. 2010–103

safer • healthier • peopletm November 2009