Overload of the lower limbs of firefighters as a result of external conditions

The work was supported by The National Centre for Research and Development* under the research grant number DOB-BIO6/05/54/2014 - Development of the sensorimotor profile and performance testing procedures for KSRG rescuers in standardized rescue activities, carried out in 2014-2018.

The presented data are part of the obtained results on the basis of which the attempts to find out to what extent the specificity of the firefighting work and experience affects the ability to reduce strain to which the musculoskeletal system is exposed when jumping from different heights (0.5 and 1 m) and to what extent does the flexor/extensor muscle torques ratio affect impact absorption in lower limbs. By identifying the relationship between H:Q ratio and landing biomechanics, this data also can be used to assess whether muscular balance may serve as a compensatory factor that reduces injury risk in dynamic tasks under load.

The data includes the results of 171 male firefighters from multiple Polish fire stations. The subjects were recruited from 01.04.2015 to 31.07.2015. Participation in the study was voluntary. All of the firefighters underwent a qualification procedure which involved filling in a questionnaire on the health status of the respondent, a cardiological and orthopedic examination.

The measurements of basic anthropometric parameters were performed, i.e. body height (bh), measured with an accuracy of 0.5 cm using an anthropometer, and body mass (bm) measured with an accuracy of 0.5 kg.

The evaluation of the overload to the musculoskeletal system was carried out for drop jumps in different external conditions. The participants performed three drop jumps onto two piezoelectric Kistler platforms at 5-second intervals, with each lower limb landing on a separate platform.

These tests were performed from two heights (0.5 and 1 m) and in two different outfits (sports and fire protection clothes). The fire protection clothes increased the load by 75 N on average. Based on three jumps, one averaged profile of vertical ground reaction forces was developed for each test. Averaging over time was performed with maintaining the total impulse of the force generated during the test.

The data contains results the max value of generated ground reaction forces (GRF), value of overload relative to body weight (GRF/BW) of the participant and time of overload affecting the musculoskeletal system (impact absorption time) were used (t>1 BW).

The respondents performed the tests in the following order: platform height of 0.5 m and 1 m, in sportswear which consisted of a T-shirt, short comfortable shorts and soft sports shoes and after using the same order (0.5 and 1 m), the tests were repeated in firefighter's protective clothing which consisted of a special suit, gloves, a helmet and stiff fireproof footwear (without the air cylinder and a gas mask).

The data contains also results of muscle torque (T) of knee jonts extensors (ext) and flexors (flex) were measured. The measurement was performed under static conditions in a sitting position and in the 90° position in the knee joint. The angle value used in the tests stemmed from the characteristics of static muscles, based on which the conditions needed for producing maximum torque are determined.

The data contains the maximum values from two isometric contractions lasting 3–5 s with a rest break of 15 s. Prior to the test, each participant did a 10-minute warm-up.

Joint stability evaluation as the flexor/extensor muscle torques ratio was calculated using the formula: H/Qratio=(1-(T_flex/T_ext))×100%,

were: Tflex – value obtained for flexors; Text – value obtained for extensors.