The purpose of the present study was to extend the knowledge offunctional linkages between visual and mental load, performance, and prefrontalcortex (PFC) activity, during forestry forwarding work. Eleven healthy participants,range 21–51 years old, with a minimum of 1-year work experience,carried out the task of loading logs along a standardized path in a machinesimulator during two counterbalanced test conditions: (i) conventional cranecontrol, and; (ii) semi-automated crane control. Mental load was assessed byquantification of oxygenated hemoglobin (HbO2) concentration changes overthe right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional nearinfrared spectrometry (fNIRS). Visual, autonomic, and motoric control variableswere measured and analyzed in parallel along with the individual level of performance.Linear Mixed Models (LMM) analysis indicated more mental loadduring conventional crane work. Collectively, our data suggest that fNIRS is aviable tool which can be used in neuroergonomic research to evaluate physiologicalactivity levels in PFC.

Background: Adults with complex congenital heart disease (CHD) show reduced aerobic exercise capacity and impaired skeletal muscle function compared with healthy peers. Peripheral muscle factors are presumed to be important contributors to the aerobic capacity, but the mechanisms are poorly understood. The aim of the present study was to investigate differences between adults with CHD and controls in muscle oxygenation kinetics at rest, and during and after exercise.

Methods: Seventy-four patients with complex CHD (mean age 35.6 ± 14.3 years, female n = 22) were recruited. Seventy-four age- and sex-matched subjects were recruited as controls. Muscle oxygenation was successfully determined on the anterior portion of the deltoid muscle using near-infrared spectroscopy in 65 patients and 71 controls. Measurements were made at rest, during isotonic shoulder flexions (0-90°) to exhaustion, and during recovery.

Results: The patients with CHD performed fewer shoulder flexions (40 ± 17 vs 69 ± 40; P < 0.001), had lower muscle oxygen saturation (StO2) at rest (58 ± 18% vs 69 ± 18%; P < 0.001), slower desaturation rate at exercise onset (−9.7 ± 5.9 vs −15.1 ± 6.5% StO2 × 3.5 s−1, P <0.001), and slower resaturation rate post exercise (4.0 ± 2.7 vs 5.4 ± 3.6% StO2 × 3.5 s−1; P = 0.009) compared with the controls. Conclusions: In comparison with age- and sex-matched controls, adults with complex CHD had slower oxygenation kinetics. This altered skeletal muscle metabolism might contribute to the impaired skeletal muscle endurance capacity shown and thereby also to the reduced aerobic capacity in this population. 

This study is concerned with a new method for partly automating forestry harvesting work. Work-related injuries and constant demands for a higher productivity are two of the many arguments for why forestry work must be improved. Forestry work places great mental demands on the driver because they must continuously evaluate and act on relevant parts in a heavy visual information flow. Against this background the purpose of the present study was to extend the knowledge of functional linkages between visual and mental fatigue, performance, and prefrontal cortex activity, during semi-automated and conventional forestry harvesting work. Eleven healthy participants, range 21–51 years old, with a minimum of 1-year work experience, carried out the task of loading logs along a standardized path in a machine simulator during two counterbalanced 45-min periods: (i) conventional forest harvesting, and; (ii) semi-automated forest harvesting. Equal emphasizes was put on accuracy and speed. During manual forest harvesting the driver controlled the crane arm, used to load logs into the load space of the forest vehicle (“forwarder”), by manually operating the joysticks and so guide the crane to the location of the log and then back to the load space. During semi-automatic forest harvesting the driver moved the crane with the press of a button to a pre-programmed location near the log and then, after another button press, to a pre-programmed location within the load space. The following joystick usage parameters were considered for the statistical analysis: Sequential work cycle number, work phase (1-loading in basket, 2-movement to log, 3-picking up log, 4-movement to load space), number of simultaneously used controls across samples of one phase, number of direction changes of joystick movements per phase. Mental load was assessed by quantification of oxygenated hemoglobin (HbO₂) concentration changes over the right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional near infrared spectrometry (fFNIRS: PortaLite mini, Artinis Medical Systems, Zetten, the Netherlands). The frequency and duration of horizontal amplitudes of eye/head/neck angles was assessed continuously with 8 SmartEye cameras and used as a measure of visual load. NASA-TLX and Borg CRS was used to assess perceived mental and physical fatigue. Linear Mixed Model will be used to test and to analyze the effect of the duration of work, joystick usage, work type (manual or semi-automated) and perceived mental and physical effort on the outcome of oxygenated hemoglobin concentration. This study contributes with new knowledge of the consequences of the current increase in automation. The 4^th industrial revolution can have tremendous implications on how we perceive and organize work in the future, but little is still known about the impact on human body and brain.

This study is concerned with a new method for partly automating forestry harvesting work. Work-related injuries and constant demands for a higher productivity are two of the many arguments for why forestry work must be improved. Forestry work places great mental demands on the driver because they must continuously evaluate and act on relevant parts in a heavy visual information flow. Against this background the purpose of the present study was to extend the knowledge of functional linkages between visual and mental fatigue, performance, and prefrontal cortex activity, during semi-automated and conventional forestry harvesting work. Eleven healthy participants, range 21–51 years old, with a minimum of 1-year work experience, carried out the task of loading logs along a standardized path in a machine simulator during two counterbalanced 45-min periods: (i) conventional forest harvesting, and; (ii) semi-automated forest harvesting. Equal emphasizes was put on accuracy and speed. During manual forest harvesting the driver controlled the crane arm, used to load logs into the load space of the forest vehicle (“forwarder”), by manually operating the joysticks and so guide the crane to the location of the log and then back to the load space. During semi-automatic forest harvesting the driver moved the crane with the press of a button to a pre-programmed location near the log and then, after another button press, to a pre-programmed location within the load space. The following joystick usage parameters were considered for the statistical analysis: Sequential work cycle number, work phase (1-loading in basket, 2-movement to log, 3-picking up log, 4-movement to load space), number of simultaneously used controls across samples of one phase, number of direction changes of joystick movements per phase. Mental load was assessed by quantification of oxygenated hemoglobin (HbO₂) concentration changes over the right dorsolateral prefrontal cortex (dlPFC) via non-invasive functional near infrared spectrometry (fFNIRS: PortaLite mini, Artinis Medical Systems, Zetten, the Netherlands). The frequency and duration of horizontal amplitudes of eye/head/neck angles was assessed continuously with 8 SmartEye cameras and used as a measure of visual load. NASA-TLX and Borg CRS was used to assess perceived mental and physical fatigue. Linear Mixed Model will be used to test and to analyze the effect of the duration of work, joystick usage, work type (manual or semi-automated) and perceived mental and physical effort on the outcome of oxygenated hemoglobin concentration. This study contributes with new knowledge of the consequences of the current increase in automation. The 4^th industrial revolution can have tremendous implications on how we perceive and organize work in the future, but little is still known about the impact on human body and brain.

To improve current understandings of physical Workload (WL) in elite Bandy, ten bandy players were monitored for heart rate (HR) during thirteen matches over one championship season. Participants were divided into five subgroups according to playing position - libero, defender, halves, midfielder and forward. HR measurements were analyzed with two different methods to compute physical WL - (i) percentage of total time spent in different HR zones (HRres) and (ii) WL based on the Edwards method. Also determined was the time spent at HR levels above the lactate threshold (LT). A one-way ANOVA was used for analysis. For WL according to the Edwards method, significant differences (p=0.05) were shown between groups with defenders presenting the highest scores and forwards and liberos the lowest. A significant difference (p=0.05) was found between liberos and halves and the other positions as to how much time they spent in zone 70-80% of HRres. In 91-100% of HRres there was a distinct difference between defenders and the other positions and also forwards differed significantly from liberos, defenders and halves (p=0.05). The libero spent only one percent of the time over the LT, whereas the midfielder spent about 27% of the time over the LT. Overall, defenders showed the greatest WL during a match and liberos the lowest. The practical implications of these findings can help coaches and trainers design training methods specific to each position as well as individualized training sessions for each player in elite bandy.

Introduction: Adults with complex congenital heart disease show reduced aerobic exercise capacity and impaired skeletal muscle function compared to healthy peers. Peripheral muscle factors are presumed to be important contributors, but the mechanisms are poorly understood. Hypothesis: Muscle oxygenation is associated with reduced skeletal muscle endurance in adults with complex CHD. Methods: Sixty-four adults with complex congenital heart disease (mean age 36.9±14.8 years, females n=19) were recruited from centers specialized in congenital heart disease. Seventy-four age and gender matched healthy peers were recruited as controls. Muscle oxygen saturation was successfully determined on the anterior portion of the deltoid muscle using near-infrared spectroscopy for 57 patients and 71 controls. Measurements were made at baseline, during isotonic shoulder flexions (0-90°) to exhaustion and during 60 seconds of recovery. Results: The adults with complex CHD performed fewer shoulder flexions (38±15 vs. 69±40, p <0.001), had lower muscle oxygen saturation at rest (58±17% vs. 69±18%, p <0.001), a slower desaturation rate at exercise onset (-9.5±5.9%/sec vs. -15.1±6.5%/sec, p <0.001), and a slower resaturation rate post exercise (3.9±2.8%/sec vs. 5.4±3.6%/sec, p =0.008) compared to the controls. Conclusions: A distinct association was found between muscle oxygenation kinetics and early muscle fatigue for adults with complex CHD. Our findings may give insight to the underlying mechanisms for the reduced aerobic exercise capacity for these patients, and therefore provide implications for design of exercise training protocols in this population. [ABSTRACT FROM AUTHOR]

Purpose: To extend our knowledge of the functional linkages between visual fatigueand regional cerebral prefrontal cortex (PFC) oxygenation, we measured time related hemodynamic changes over the right dorsolateral prefrontal cortex (dlPFC) duringconvergence load under conflicting stimulus-to-accommodation and stimulus-tovergence eye movements with and without concurrent mental load.

Methods: Twenty healthy participants with a median age of 28 years (range:18–44 years) fixated upon a vertical bar presented separately to the left andright eyes, using polarized filters, during four counterbalanced 10-min periods:(i) no accommodation/vergence conflict (Control, Ctrl); (ii) added convergenceload and accommodation/vergence conflict (Conv); (iii) added cognitive load only(Cog) and; (iv) a combination of added cognitive and convergence load andaccommodation/vergence conflict (Cc). Viewing distance was 65 cm. Non-invasivemeasurements of hemodynamic activity over the dlPFC were quantified by functionalnear-infrared spectroscopy (fNIRS). During the two-convergence load conditions, thehorizontal disparity of the two bars varied dynamically from no disparity to a disparityset 20% below the individual threshold for diplopia. Cognitive load was induced by then-back-2 test which required the subject to memorize and recall the changing colorsof the horizontal bars and decide when a given color was the same as that occurring two colors previously. fNIRS data were averaged over 10-s windows centered at 0, 2,4, 6, 8, and 10 min of each task, subtracted from a 20-s baseline window immediatelypreceding the visual task, and then represented as changes in oxygenated hemoglobin(ΔHbO2); deoxygenated hemoglobin (ΔHHb) and total hemoglobin (ΔtHb).

Results: Linear mixed model analyses showed that hemodynamic activity wassystematically influenced by time (p < 0.001). The group-averaged time-related levelof change across the viewing conditions did not differ when compared with one another(p > 0.05). Larger convergence eye-movement responses under conflicting stimulus-to accommodation,and stimulus-to-vergence over time, increased ΔHbO2 and ΔtHb onlyin condition Cc and after 8 min of task time (p < 0.10 for min^-6 and min^-8: p < 0.05 for min^-10).

Discussion: Collectively, our data suggest that HbO2, HHb, and tHb, recorded over the dlPFC with fNIRS, can be used to assay the degree to which supervisory oculomotorcontrol processes are activated during visually deficient near work.

Fatigue is a phenomenon of pronounced importance in sports. Recently, there is strong evidence of interplay between the prefrontal cortex and motor output during fatiguing contractions. The dorsolateral prefrontal cortex (DLPC) due to its large involvement in cognitive and motor activities is believed to be involved but this requires physiological clarification. AIM: We investigated the relationship between DLPC activity - responses in oxyhemoglobin (HbO2) and total hemoglobin (HbT) measured by near-infrared spectroscopy (NIRS), and the vastus lateralis muscle (VL) activity - quantified as root-mean-square (RMS) of the EMG signal, during a fatigue protocol.

METHODS: Four male runners (32±12 yrs) with probes for NIRS over the DLPC and EMG over the VL performed a track running test at a constant speed to fatigue (exhaustion). The running speed was individually determined as the average speed of a 1200-m time trial performed ~3 days prior to testing. For NIRS changes in μmole/L of HbO2 and HbT were computed. The VL EMG-RMS of the contraction of each step was normalized as a percent of a submaximal reference contraction (%RMS), thus removing the non-activity between steps. Data of 10s epochs at 20, 40, 60, 80 and 100% of time for each lap were averaged for analyses. Regression analyses performed with HbO2 and with HbT as dependent variables and %RMS as the independent variable.

RESULTS: Over time there was an increase in HbO2 and HbT in the DLPC, and in VL-%RMS. Both HbO2 and HbT correlated strongly with EMG-RMS during running to fatigue (see figures below); p<0.001 for both.

CONCLUSION: The strong relationship between DLPC and VL activities during running to fatigue suggests the involvement of the DLPC in the central processing of fatigue.