Wearable device for continuous sweat lactate monitoring in sports: a narrative review.

In sports science, the use of wearable technology has facilitated the development of new approaches for tracking and assessing athletes' performance. This narrative review rigorously explores the evolution and contemporary state of wearable devices specifically engineered for continuously monitoring lactate levels in sweat, an essential biomarker for appraising endurance performance. Lactate threshold tests have traditionally been integral in tailoring training intensity for athletes, but these tests have relied on invasive blood tests that are impractical outside a laboratory setting. The transition to noninvasive, real-time monitoring through wearable technology introduces an innovative approach, facilitating continuous assessment without the constraints inherent in traditional methodologies. We selected 34 products from a pool of 246 articles found through a meticulous search of articles published up to January 2024 in renowned databases: PubMed, Web of Science, and ScienceDirect. We used keywords such as "sweat lactate monitoring," "continuous lactate monitoring," and "wearable devices." The findings underscore the capabilities of noninvasive sweat lactate monitoring technologies to conduct long-term assessments over a broad range of 0-100 mM, providing a safer alternative with minimal infection risks. By enabling real-time evaluations of the lactate threshold (LT) and maximal lactate steady state (MLSS), these technologies offer athletes various device options tailored to their specific sports and preferences. This review explores the mechanisms of currently available lactate monitoring technologies, focusing on electrochemical sensors that have undergone extensive research and show promise for commercialization. These sensors employ amperometric reactions to quantify lactate levels and detect changes resulting from enzymatic activities. In contrast, colorimetric sensors offer a more straightforward and user-friendly approach by displaying lactate concentrations through color alterations. Despite significant advancements, the relationship between sweat lactate and blood lactate levels remains intricate owing to various factors such as environmental conditions and the lag between exercise initiation and sweating. Furthermore, there is a marked gap in research on sweat lactate compared to blood lactate across various sports disciplines. This review highlights the need for further research to address these shortcomings and substantiate the performance of lactate sweat monitoring technologies in a broader spectrum of sports environments. The tremendous potential of these technologies to supplant invasive blood lactate tests and pioneer new avenues for athlete management and performance optimization in real-world settings heralds a promising future for integrating sports science and wearable technology.

Transcranial Direct Current Stimulation of Motor Cortex Enhances Spike Performances of Professional Female Volleyball Players.

The purpose of this study was to investigate effects of brain excitability by transcranial direct current stimulation (tDCS) on spike performances of professional female volleyball players. Thirteen professional female volleyball players were recruited for participation. We performed a randomized single-blind, SHAM-stimulus controlled, and counter-balanced crossover design with two interventions in this study. An anodal tDCS current was applied over the primary motor cortex (M1) for 20 min at 2 mA. In the SHAM intervention, the current was first applied for 30 s, after which it was terminated. Exercise performance assessment which comprised spike performance (spike ball speed, spiking consistency), two vertical jumps (jump and reach: JaR, countermovement jump: CMJ), bench-press and back-squat one-repetition maximum (1RM) were tested pre- and post-intervention. Results indicated that spike ball speed and spiking consistency following tDCS were significantly higher than those after SHAM intervention (both p < 0.05). However, JaR and CMJ did not show any significant differences between tDCS and SHAM intervention groups (both p > 0.05). There was no significant difference in bench-press and back-squat 1RM between two groups either (both p > 0.05). These findings suggest that tDCS could be effective in enhancing motor coordination performances of professional female volleyball athletes.

High-Intensity Warm-Up Increases Anaerobic Energy Contribution during 100-m Sprint.

This study aimed to evaluate the effects of warm-up intensity on energetic contribution and performance during a 100-m sprint. Ten young male sprinters performed 100-m sprints following both a high-intensity warm-up (HIW) and a low-intensity warm-up (LIW). Both the HIW and LIW were included in common baseline warm-ups and interventional warm-ups (eight 60-m runs, HIW; 60 to 95%, LIW; 40% alone). Blood lactate concentration [La-], time trial, and oxygen uptake (VO2) were measured. The different energy system contribution was calculated by using physiological variables. [La-1]Max following HIW was significantly higher than in LIW (11.86 ± 2.52 vs. 9.24 ± 1.61 mmol·L-1; p < 0.01, respectively). The 100-m sprint time trial was not significantly different between HIW and LIW (11.83 ± 0.57 vs. 12.10 ± 0.63 s; p > 0.05, respectively). The relative (%) phosphagen system contribution was higher in the HIW compared to the LIW (70 vs. 61%; p < 0.01, respectively). These results indicate that an HIW increases phosphagen and glycolytic system contributions as compared to an LIW for the 100-m sprint. Furthermore, an HIW prior to short-term intense exercise has no effect on a 100-m sprint time trial; however, it tends to improve times (decreased 100-m time trial; -0.27 s in HIW vs. LIW).

Energy System Contributions and Physical Activity in Specific Age Groups during Exergames.

Exergames have been recommended as alternative ways to increase the health benefits of physical exercise. However, energy system contributions (phosphagen, glycolytic, and oxidative) of exergames in specific age groups remain unclear. The purpose of this study was to investigate the contributions of three energy systems and metabolic profiles in specific age groups during exergames. Seventy-four healthy males and females participated in this study (older adults, n = 26: Age of 75.4 ± 4.4 years, body mass of 59.4 ± 8.7 kg, height of 157.2 ± 8.6 cm; adults, n = 24: Age of 27.8 ± 3.3 years, body mass of 73.4 ± 17.8 kg, height of 170.9 ± 11.9 cm; and adolescents, n = 24: Age of 14 ± 0.8 years, body mass of 71.3 ± 11.5 kg, height of 173.3 ± 5.2 cm). To evaluate the demands of different energy systems, all participants engaged in exergames named Action-Racing. Exergames protocol comprised whole-body exercises such as standing, sitting, stopping, jumping, and arm swinging. During exergames, mean heart rate (HRmean), peak heart rate (HRpeak), mean oxygen uptake (VO2mean), peak oxygen uptake (VO2peak), peak lactate (Peak La-), difference in lactate (ΔLa-), phosphagen (WPCr), glycolytic (WLa-), oxidative (WAER), and total energy demands (WTotal) were analyzed. The contribution of the oxidative energy system was higher than that of the phosphagen or glycolytic energy system (65.9 ± 12% vs. 29.5 ± 11.1% or 4.6 ± 3.3%, both p < 0.001). The contributions of the total energy demands and oxidative system in older adults were significantly lower than those in adults and adolescents (72.1 ± 28 kJ, p = 0.028; 70.3 ± 24.1 kJ, p = 0.024, respectively). The oxidative energy system was predominantly used for exergames applied in the current study. In addition, total metabolic work in older adults was lower than that in adolescents and adults. This was due to a decrease in the oxidative energy system. For future studies, quantification of intensity and volume is needed to optimize exergames. Such an approach plays a crucial role in encouraging physical activity in limited spaces.

The Relationship Between Foot Feature Parameters and Postural Stability in Healthy Subjects.

OBJECTIVE: Little has been explored about the disparate contribution of medial longitudinal arch (MLA) and lateral longitudinal arch (LLA) to human gait and postural stability. This study aims to investigate the correlation of foot feature parameters including both MLA and LLA with postural stability. METHOD: Thirteen young and healthy subjects participated in this study. The newly developed FFMS extracted foot feature parameters in nonweight-bearing (NWB) and weight-bearing (WB) conditions along with postural stability parameters in single-leg-standing (SLS) condition. A bivariate correlation analysis was carried out to investigate the correlation between the foot characteristics and the postural stability parameters. RESULTS: The foot length and width showed negative correlation with center of pressure (CoP) distance in medio-lateral (ML) and total direction, whereas the foot length in NWB and WB conditions, and the foot width in WB condition showed positive correlation with CoP distance in anterior-posterior (AP) direction. The height of the LLA curve and the area of the MLA were correlated with the postural stability parameters in AP direction. The ratios of the LLA height and area showed moderate correlation with the CoP distance in ML direction and total direction. CONCLUSION: The size of a foot, such as the length and width, is correlated with postural stability. Whereas the MLA features are associated with postural stability in AP direction, the LLA features are associated with that in ML and total direction. APPLICATION: The findings suggest that the roles and contributions of the MLA and LLA features in and to the postural control are different.

Relationships between presynaptic inhibition and static postural sway in subjects with and without diabetic neuropathy.

[Purpose] Diabetic peripheral neuropathy can often lead to balance impairment. The spinal reflex is a mechanism that is reportedly important for balance, but it has not been investigated in diabetic peripheral neuropathy patients. Moreover, inhibitory or facilitatory behavior of the spinal reflex-known as presynaptic inhibition-is essential for controlling postural sway. The purpose of this study was to compare the differences in as presynaptic inhibition and balance in subjects with and without diabetic peripheral neuropathy to determine the influence of presynaptic inhibition on balance in diabetic peripheral neuropathy patients. [Subjects and Methods] Presynaptic inhibition and postural sway were tested in eight patients (mean age, 58±6 years) and eight normal subjects (mean age, 59±7 years). The mean percent difference in conditioned reflex amplitude relative to the unconditioned reflex amplitude was assessed to calculate as presynaptic inhibition. The single-leg balance index was measured using a computerized balance-measuring device. [Results] The diabetic peripheral neuropathy group showed lower presynaptic inhibition (47±30% vs. 75±22%) and decreased balance (0.65±0.24 vs. 0.38±0.06) as compared with the normal group. No significant correlation was found between as presynaptic inhibition and balance score (R=0.37). [Conclusion] Although the decreased as presynaptic inhibition observed in diabetic peripheral neuropathy patients may suggest central nervous system involvement, further research is necessary to explore the role of presynaptic inhibition in decreased balance in diabetic peripheral neuropathy patients.

Whole body vibration therapy for painful diabetic peripheral neuropathy: a pilot study.

The unsatisfactory results associated with conventional treatments for symptoms of diabetic peripheral neuropathy (DPN) demonstrate a need for research into alternative therapies. The purpose of this study was to determine the efficacy of whole body vibration therapy (WBV) as a treatment for pain associated with DPN. Participants (n = 8) with painful DPN received three treatment sessions per week for four weeks. Each session consisted of four bouts of 3 min of vibration (frequency 25 Hz, amplitude 5 mm). The primary outcome measures were changes in the visual analog pain scale (VAS) and changes in the neuropathic pain scale (NPS). WBV demonstrated a significant (p < 0.05) acute pain reduction in the VAS, and a significant chronic reduction in both the VAS and NPS scales. No side-effects were observed during this study. WBV appears to be an effective, non-invasive treatment for pain associated with DPN.

A systematic review: the effects of podiatrical deviations on nonspecific chronic low back pain.

Lower back pain (LBP) is a widespread, expensive, and debilitating problem in Western industrialized countries. Though LBP can be caused by acute injuries, biomechanical discrepancies have also been indicated to cause chronic LBP. A possible link between podiatrical deviations and LBP has been established in the literature; yet, no comprehensive review investigating the effects of foot and ankle deviations on low back pain has been published. The aim of this study was to assess the relevant literature concerning the effects of foot and ankle deviations on LBP. After review, it was determined that there is limited research regarding ankle and foot deviations and their connection to LBP. Reviewed studies have linked flat feet, ankle instability, sagittal plane blockage and excessive pronation to LBP. Specifically, excessive pronation has been shown to cause leg length discrepancies leading to pelvic tilts and LBP. Based on these results, ankle and foot deviations can be considered a potential cause for LBP due to the disruption of the kinetic chain from the foot to the back. Clinicians should consider the foot and ankle when addressing LBP, especially if more conventional etiologies fail to describe the condition.

Case study: use of vibration therapy in the treatment of diabetic peripheral small fiber neuropathy.

The aim of the study was to describe a case of type II diabetic peripheral small fiber neuropathic pain treated with whole body vibration therapy after a failed trial of conventional drugs and interventional pain management. A 64-year-old male had chronic diabetic peripheral neuropathic pain in his both feet for about 2 years. The patient tried multiple pain medications and various interventional pain treatments without significant pain relief. After 4 weeks of vibration treatment, which targeted the feet the patient's pain level and gait patterns significantly improved. These findings illustrate the importance of considering whole body vibration as a complimentary treatment in patients with diabetic peripheral neuropathic pain.

Reliability of presynaptic inhibition in patients with diabetic peripheral neuropathy.

There has been rising interest in evaluating spinal reflex activity within the clinical population, however no study has yet investigated the reliability of presynaptic inhibition (PI) on patients with diabetic peripheral neuropathy (DPN). Because neuropathy is closely related to central nervous system modification, it is important to understand the mechanism of spinal reflex activity in the DPN population. Therefore, the purpose of the study was to evaluate the reliability of PI in patients with DPN. Eight participants (58.24 ± 6.38 yrs.) diagnosed with either type I or type II diabetes and peripheral neuropathy were recruited for the study. Each subject's H-reflex was measured using an EMG to elicit and record a series of 10 paired reflex depression trials. Reliability was measured by calculating Intra Class Correlation Coefficients (ICCs) with a 95% confidence interval. The results showed excellent reliability in both intraday (0.94) and interday (0.88) reliability. Therefore, analyzing PI in the central nervous system allows for an accurate evaluation of spinal cord circuitry in a non-invasive manner.

Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function.

Proprioceptive neuromuscular facilitation (PNF) is common practice for increasing range of motion, though little research has been done to evaluate theories behind it. The purpose of this study was to review possible mechanisms, proposed theories, and physiological changes that occur due to proprioceptive neuromuscular facilitation techniques. Four theoretical mechanisms were identified: autogenic inhibition, reciprocal inhibition, stress relaxation, and the gate control theory. The studies suggest that a combination of these four mechanisms enhance range of motion. When completed prior to exercise, proprioceptive neuromuscular facilitation decreases performance in maximal effort exercises. When this stretching technique is performed consistently and post exercise, it increases athletic performance, along with range of motion. Little investigation has been done regarding the theoretical mechanisms of proprioceptive neuromuscular facilitation, though four mechanisms were identified from the literature. As stated, the main goal of proprioceptive neuromuscular facilitation is to increase range of motion and performance. Studies found both of these to be true when completed under the correct conditions. These mechanisms were found to be plausible; however, further investigation needs to be conducted. All four mechanisms behind the stretching technique explain the reasoning behind the increase in range of motion, as well as in strength and athletic performance. Proprioceptive neuromuscular facilitation shows potential benefits if performed correctly and consistently.

Reliability of the sitting hand press-up test for identifying and quantifying the level of scapular medial border posterior displacement in overhead athletes.

BACKGROUND: The lack of proper scapular kinematics can limit the function of the entire shoulder complex.(1,3) Many forms of scapular dyskinesis have been proposed along with tests to measure for the position and motion associated with those positional and movement faults (2,4-6). While scapular internal rotation has been listed among the forms of scapular dyskinesis there has not been a reliable test documented in the literature that examines this motion. The purpose of this study was to determine whether an innovative scapular medial border posterior displacement measurement device has adequate inter-rater and intra-rater reliability when used at rest and during the sitting hand press up test. METHODS: 16 male Division III baseball players free of upper limb injury for the previous 12 months participated in the study. Posterior scapular displacement measures were taken on each subject in a resting static posture and while performing a sitting hand press up test. Subjects were tested twice within 24 hours by two separate examiners. Intraclass correlation coefficients (ICC) were calculated to determine intra-rater and inter-rater reliability. RESULTS: The intra-rater reliability for rater 1 was .97 (95% confidence interval [CI]= .91-.98), for the rest position and .95 (95% CI= .86-.98) for the sitting hand press-up position. Intra-rater reliability for rater 2 was .99 (95% CI= .97-.99) for the rest position and .98 (95% CI=. 95-.99) for the sitting hand press-up position. The ICCs for inter-rater reliability of the scapular medial border posterior displacement measurement in at the rest position and the sitting hand press-up position were .89 (95% CI= .81-.96) and .89 (95% CI= .80-.96) respectively. CONCLUSIONS: The findings of this study indicate that the measurement of medial border posterior displacement using this device demonstrates good to excellent inter-rater and intra-rater reliability.