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Purpose: This pilot study investigated the functional outcomes after ischemic preconditioning (IPC) in high-level para-athletes with spinal-cord injury. Methods: Nine athletes completed 2 handgrip exercise trials (an isometric hold to failure at 60% maximal voluntary contraction [ISO] and a progressive, intermittent handgrip to failure [INT]), preceded by either IPC (220 mm Hg) or sham (20 mm Hg) for six 5-minute periods, in a repeated-measures, crossover design. Results: Although small performance improvements in time to task failure were observed in the ISO (∼5%) and INT (∼8%) IPC conditions, which are similar to those reported elsewhere, no statistical influence was observed (ISO–IPC, 74.2 [32.6] s; SHAM, 70.7 [27.2] s; P = .73; INT–IPC, 426.0 [80.1] s; SHAM, 392.2 [42.5] s; P = .35). Fatigue was evident in the forearm muscle force (maximal voluntary contraction) ISO (mean decline of 178.1 [76.0] N [95% CI, −10.4 to 366.7 N]; P < .05) and INT (mean decline of 182.2 [72.5] N [95% CI, 34.5–329.8 N]; P < .05) trials but not different between treatments (P > .95). Conclusions: Although small performance improvements in time to task failure were observed, the findings of the present data set suggest that acute bouts of IPC do not meaningfully influence fatigue during handgrip exercise in para-athletes with spinal-cord injury.

Purpose: Continuous glucose monitors (CGMs) are becoming increasingly popular among endurance athletes despite unconfirmed accuracy. We assessed the concurrent validity of the FreeStyle Libre 2 worn on 2 different sites at rest, during steady-state running, and postprandial. Methods: Thirteen nondiabetic, well-trained recreational runners (age = 40 [8] y, maximal aerobic oxygen consumption = 46.1 [6.4] mL·kg^–1·min^–1) wore a CGM on the upper arm and chest while treadmill running for 30, 60, and 90 minutes at intensities corresponding to 50%, 60%, and 70% of maximal aerobic oxygen consumption, respectively. Glucose was measured by manually scanning CGMs and obtaining a finger-prick capillary blood glucose sample. Mean absolute relative difference, time in range, and continuous glucose Clarke error grid analysis were used to compare paired CGM and blood glucose readings. Results: Across all intensities of steady-state running, we found a mean absolute relative difference of 13.8 (10.9) for the arm and 11.4 (9.0) for the chest. The coefficient of variation exceeded 70%. Approximately 47% of arm and 50% of chest paired glucose measurements had an absolute difference ≤10%. Continuous glucose Clarke error grid analysis indicated 99.8% (arm) and 99.6% (chest) CGM data fell in clinically acceptable zones A and B. Time-in-range analysis showed reduced accuracy at lower glucose levels. However, CGMs accurately detected trends in mean glucose readings over time. Conclusions: CGMs are not valid for point glucose monitoring but appear to be valid for monitoring glucose trends during steady-state exercise. Accuracy is similar for arm and chest. Further research is needed to determine whether CGMs can detect important events such as hypoglycemia during exercise.

Purpose: To study whether, during typical-level running, non-rear-foot strikers (non-RFS) or rear-foot strikers (RFS) presented a similar or different extent of neuromuscular fatigue after a prolonged graded run. Methods: Sixteen experienced male trail runners (8 non-RFS and 8 RFS) performed a 2.5-hour treadmill graded running exercise. Before and after exercise, neuromuscular tests were performed to assess neuromuscular fatigue of the plantar flexors. Biomechanical gait parameters were acquired with an instrumented treadmill, and electromyographic activity of the lower-limb muscles was collected as an index of muscle activation. Results: There were no significant time × foot strike interactions for neuromuscular (all P ≥ .742), muscle activation (all P ≥ .157), or biomechanical (all P ≥ .096) variables. Conclusions: A dominant level running foot-strike pattern did not directly affect the extent of neuromuscular fatigue during a prolonged graded run. This suggests that no ideal running foot-strike pattern exists to minimize neuromuscular fatigue during prolonged-duration races wherein cumulative uphill and downhill segments are high, such as in trail running.

Purpose: To examine the reproducibility and sensitivity of a self-paced field running test (SFT) in monitoring positive and negative changes in endurance performance. Methods: A total of 27 (11 women) recreational runners participated in a 6-week training intervention. The intervention was divided into a 3-week baseline period, a 2-week overload period, and a 1-week recovery period. An incremental treadmill test was performed before the baseline period and a 3000-m running test before and after all periods (T1–T4). In addition, the participants performed once a week an SFT (SFT1–6), which consisted of submaximal (6 + 6 + 3-min test at perceived exertion of 9/20, 13/20, and 17/20) and maximal sections (6 × 3-min intervals at maximum sustainable effort). The associations between the incremental treadmill test and the SFT1 performance were examined with the Pearson correlation, and the intraclass correlation was analyzed for the parameters of SFT1 to SFT3 sessions during the baseline period. The repeated-measures correlation was calculated for the 3000-m speed at T1 to T4 and the corresponding speeds at SFT. Results: Significant associations (r = .68–.93; P < .001) were found between the speeds of the SFT and the peak and lactate threshold speeds of the incremental treadmill test. Intraclass correlations varied between .77 and .96, being the highest for the average speed of 6 × 3-minute intervals. Repeated-measures correlation was significant (P < .05) for the 9/20 (r = .24), 13/20 (r = .24), and 6 × 3-minute intervals (r = .29). Conclusions: The SFT seemed a reproducible method to estimate endurance performance in recreational runners. The sensitivity to track short-term and small-magnitude changes in performance seems more limited and might require more standardized conditions.

Purpose: To investigate the effect of a newly developed hand rim in wheelchair tennis players from a lab and field perspective. Methods: Nine wheelchair tennis players performed a set of field and lab tests with the new rim (NR) and regular rim on the racket side. Each player had a 60- to 120-minute regular training session with the NR. Three wheelchair tennis field tests (20-m sprint, Illinois, spider) were completed on a hard court using inertial measurement units. The inertial measurement units enabled analysis of linear/rotational velocity and acceleration. In the lab, two 4-minute submaximal tests (at 1.5 and 2 m/s, 0.2 W/kg), followed directly by a 5-second sprint, on a wheelchair ergometer were completed. Force and velocity were measured continuously throughout all tests. Mixed linear models investigated the effect between the 2 hand rims. Results: During the spider test, mean rotational velocity to the racket side (−2%, P = .005) was lower in the NR, and end times were similar between hand-rim conditions. No differences were observed in the 20-m sprint and Illinois field tests. In the lab, contact angle (+6%, P = .04), cycle time (+12%, P = .007), and work per push (+13%, P = .005) were higher in the NR during submaximal propulsion. Work per push (+13%, P = .007), peak velocity (+3%, P < .001), and distance covered (+4%, P = .02) were higher with the NR during the 5-second sprint test. Conclusions: The NR seems slightly favorable compared with the regular rim during performance testing on a wheelchair ergometer in wheelchair tennis players. A longer practice time might show more insights between the hand-rim types.

Objectives: Assess the effect of water dousing on heat strain and performance during self- and fixed-paced exercise in the heat. Design: Crossover, block-randomized controlled trial. Methods: Thirteen trained runners completed a 10-km time trial (TT) and 60-minute fixed-pace run (60% velocity of $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ ) in a 30.4 °C, 47.4% relative humidity environment using either water dousing (DOUSE) or no dousing (CON). Results: Ten-kilometer TT performance was faster in DOUSE compared to CON (44:11 [40:48, 47:34] vs 44:38 [41:21, 47:56] min:s; P = .033). Change in core temperature (T _c ) was not different between groups during the TT (+0.02 [−0.04, 0.07] °C in DOUSE; P = .853) or fixed-pace run (+0.02 [−0.15, 0.18] °C; P = .848). Change in mean skin temperature was lower in DOUSE during the TT (−1.80 [−2.15, −1.46] °C; P < .001) and fixed-pace run (−1.38 [−1.81, −0.96] °C; P < .001). Heart rate was lower for DOUSE during the fixed-pace run (−3.5 [−6.8, −0.2] beats/min; P = .041) but not during the TT (−0.2 [−2.5, 2.1] beats/min; P = .853). Thermal sensation was lower for DOUSE during the TT (−49.3 [−72.1, −26.1] mm; P < .001) and fixed-pace run (−44.7 [−59.7, −29.6] mm; P < .001). Rating of perceived exertion was not different between groups for the TT (−0.2 [−0.7, 0.3]; P = .390) or fixed-pace run (−0.2 [−0.8, 0.4]; P = .480). Sweat rate was lower for DOUSE for the TT (−0.37 [−0.53, −0.22] L/h; P < .001) and fixed-pace run (−0.37 [−0.48, −0.26] L/h; P < .001). Conclusion: Water dousing improves 10-km TT performance in the heat but does not affect T _c . The positive change in thermal perception (via lower skin temperature) during the TT likely drives this benefit.

Purpose: We investigated the effects of manipulating running velocity and hypoxic exposure on vastus lateralis muscle oxygenation levels during treadmill running. Methods: Eleven trained male distance runners performed 7 randomized runs at different velocities (8, 10, 12, 14, 16, 18, and 20 km·h⁻¹), each lasting 45 seconds on an instrumented treadmill in normoxia (fraction of inspired oxygen [FiO₂] = 20.9%), moderate hypoxia (FiO₂ = 16.1%), high hypoxia (FiO₂ = 14.1%), and severe hypoxia (FiO₂ = 13.0%). Continuous assessment of Tissue Saturation Index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, changes in TSI (ΔTSI) data over the final 20 seconds of each run were compared between velocities and conditions. Results: There was a significant velocity × condition interaction for ΔTSI% (P < .001, ${\eta }_{\mathrm{p}}^2=.19$ ), with a smaller ΔTSI% decline in normoxia compared with high hypoxia and severe hypoxia at 8 km·h⁻¹ (g = 1.30 and 1.91, respectively), 10 km·h⁻¹ (g = 0.75 and 1.43, respectively), and 12 km·h⁻¹ (g = 1.47 and 1.95, respectively) (pooled values for all conditions: P < .037). The ΔTSI% decline increased with each subsequent velocity increment from 8 km·h⁻¹ (−9.2% [3.7%]) to 20 km·h⁻¹ (−22.5% [4.1%]) irrespective of hypoxia severity (pooled values for all conditions: P < .048). Conclusions: Running at slower velocities in conjunction with high and severe hypoxia reduces vastus lateralis muscle oxygenation levels. Muscle ΔTSI% proves to be a sensitive indicator, underscoring the potential use of near-infrared spectroscopy as a reference index of internal load during treadmill runs.