Low back pain and biomechanical characteristics of back muscles in firefighters.

Firefighters often experience low back pain (LBP), but their back muscle characteristics are not well studied. This study aimed to 1) compare the biomechanical characteristics of back muscles and self-reported back disabilities in frontline firefighters with and without LBP history, and 2) examine the relationships between back disability and biomechanical measurements. We recruited 42 male firefighters and assessed their perceived pain and disabilities, maximum isometric back extension strength, passive stiffness, and fatigability of the longissimus. 54.8% of the participants experienced LBP within the past year. Those indicating higher pain intensity also had greater disability as indicated by the Oswestry Disability Index. There were no significant differences in strength, stiffness or fatigability of the back muscles between firefighters with and without LBP history. Multiple linear regression analysis revealed no significant relationship between the back disability and any biomechanical or demographic measures, likely due to the high functional abilities of the participants.

Approximately 50% of the firefighters who participated in the study experienced low back pain in the past 12 months. Since the pain level was mild to moderate, most of them continued to report to work. Biomechanically, there were no differences in back muscle strength, stiffness, resistance to fatigue, or left-right symmetry between firefighters with and without back pain history. Back disabilities were not related to any biomechanical measures or demographics including age and body mass index. Overall, despite experiencing some back pain, these frontline firefighters are highly functional and did not show diminished physical or neuromuscular responses.

Effects of foot orthosis on ground reaction forces and perception during short sprints in flat-footed athletes.

Prefabricated foot orthosis (FO) is commonly worn for flat foot management. This study aimed to investigate the kinetic and perceptual effects of wearing prefabricated FO among flat-footed athletes during bouts of sprints. Twenty male sprint-based sports athletes who had flat foot bilaterally ran at three test speeds (5, 6, 7 m/s) under two conditions: prefabricated FO and sham FO. Ground reaction force (GRF) variables and subjective perceptions were recorded. Kinetic variability of GRF variables were computed to indicate step-to-step variance. Biomechanically, wearing prefabricated FOs increased vertical impact force (p =.005), loading rate (p =.001), and kinetic variability of peak propulsive force (p =.038) and loading rate (p =.019) during sprinting speeds across 5 to 7 m/s. Subjectively, prefabricated FO provided better arch support (p =.001) but resulted in reduced forefoot cushioning (p =.001), heel cushioning (p =.002), and overall comfort (p =.008).

Between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights.

This study investigated the between-limb asymmetry in kinetic and temporal characteristics during bilateral plyometric drop jumps from different heights. Seventeen male basketball players performed drop jumps from 3 heights on two platforms in randomized orders. Vertical ground reaction force data were analysed with respect to the lead limb (i.e. the limb stepping off the raised platform first) and trail limb. Peak forces and loading rates of each limb were calculated. The absolute time differential between the two limbs at initial ground contact and takeoff were determined. The frequency of symmetrical landing and taking off with "both limbs together" were counted using 3 time windows. Results showed that the lead limb displayed higher peak forces and loading rates than the trail limb across all heights (p <.05). As drop height increased, the absolute time differentials decreased at initial ground contact (p <.001) but increased at takeoff (p =.035). The greater the preset time window, the more landings and takeoffs were classified as bilaterally symmetrical. In conclusion, higher drop heights allowed subjects to become more bilaterally symmetrical in the timing of landing but this reduction in temporal asymmetry did not accompany with any reduction in kinetic asymmetry.

Effect of caffeine ingestion on free-throw performance in college basketball players.

BACKGROUND: It is currently unclear whether pre-exercise caffeine ingestion can improve free-throw shooting performance, a vital skill in basketball. The purpose of this study was to investigate the effects of caffeine on free-throw shooting performance in college-aged basketball players. METHODS: Twelve males (23.1 ± 1.9 years; 180.1 ± 8.8 cm; 77.1 ± 12.4 kg) and six females (22.0 ± 1.3 years; 169.4 ± 8.9 cm; 67.0 ± 11.1 kg) who competed at the college level ingested 6 mg per kg of body mass of (a) caffeine or (b) maltodextrin (placebo) on two separate occasions in a random order. After 60 min, they performed five sets of a match-simulated basketball protocol comprising six sideline-to-sideline sprints on a standard basketball court followed by two free-throws after each set. The number of successful shots was counted. Heart rate and rating of perceived exertion (RPE) after each sprint set were also recorded. RESULTS: Caffeine ingestion did not improve overall free-throw success (caffeine = 6.1 ± 1.7 vs. placebo = 5.5 ± 2.0; p = 0.34) compared with placebo across all five sets. There was no change in shooting accuracy across sprint sets in either trial despite significant increases in both heart rate and RPE. Caffeine increased heart rate (p = 0.02) but had no effect on RPE (p = 0.57) across five sets compared with placebo. CONCLUSIONS: Ingestion of 6 mg of caffeine per kg of body mass did not improve basketball free-throw performance. Free-throw performance did not deteriorate with increasing number of sprint sets.

Prediction of VO2max based on a 3-kilometer running test for water sports athletes.

BACKGROUND: No studies have reported the 3-kilometer running test (3KRT) intending to predict VO2max for water sports athletes. Therefore, the purpose of this study was to develop a new model to predict the maximal aerobic capacity (VO2max) for water sports athletes based on 3KRT. METHODS: One hundred and two water sports athletes completed two sessions of experiments consisting of a maximal graded exercise test (GXT) and a 3KRT. Multiple linear regression was applied to predict VO2max value based on the performance and physiological responses of 3KRT, along with participants' anthropometric and demographic variables. The predicted residual error sum of square (PRESS) and error terms (constant error and total error) were calculated to further evaluate the predictive accuracy. RESULTS: Two significant prediction models based on elapsed exercise time (T3KRT), post-exercise heart rate (PHR3KRT), body mass, and gender were proposed. One model including PHR3KRT was identified (VO2max=120.77-0.028×T3KRT [second]-0.11×PHR3KRT [bpm]-0.334×body mass [kg]+8.70×gender [1: male, 0: female]), with an adjusted R2 of 0.723. Another model excluding PHR3KRT was also identified (VO2max=103.65-0.034×T3KRT [second]-0.317×Body mass [kg] + 7.89×gender [1: male, 0: female]), with an adjusted R2 of 0.713. Both models were further validated by the result of PRESS statistics. CONCLUSIONS: This endurance 3-kilometer running test accurately predicted VO2max value for water sports athletes (rowers, canoeists, and kayakers), and the model excluding PHR3KRT would be easier to use.

Test-retest reliability of a clinical foot assessment device for measuring first metatarsophalangeal joint quasi-stiffness.

BACKGROUND: The stiffness of the first metatarsophalangeal joint (MTPJ) is of interest in cases such as hallux rigidus and apropulsive gait. Subjective rating of joint mobility as 'hypermobile, normal, or stiff' is an unreliable method. Previous instruments for the assessment of first MTPJ stiffness can be too hard and uncomfortable for test subjects. Recently, a new device using a load cell and optical fiber with fiber Bragg grating (FBG) sensors was developed to provide a comfortable means of clinical foot assessment. This study aimed to evaluate the test-retest reliability of this FBG-load cell device in measuring the first MTPJ quasi-stiffness. METHODS: The left foot of 13 female subjects were measured twice for their first MTPJ quasi-stiffness, approximately seven days apart. The FBG-load cell device measured the MTPJ range of motion from a resting position to maximum dorsiflexion and then returning to the resting start-position. The force applied by a clinician to displace the toe was simultaneously recorded using the load cell. The quasi-stiffness over the "working range" in loading and unloading directions were determined from the slope of the torque-angular displacement graph. The test-retest reliability of the MTPJ quasi-stiffness was evaluated using intra-class correlation coefficient [ICC (2,1)]. RESULTS: The reliability was almost perfect for MTPJ quasi-stiffness over the loading phase (ICC = 0.814), moderate for MTPJ quasi-stiffness over the unloading phase (ICC = 0.477) and moderate for MTPJ maximum range (ICC = 0.486). CONCLUSION: The foot assessment device comprising FBG and load cell was able to reliably measure the first MTPJ quasi-stiffness in a clinical setting. The measurement reliability was higher during the loading phase than the unloading phase.