Treatment side affects exercising microvascular oxygenation response in active breast cancer survivors: A pilot study.

Cancer treatment is associated with cardiovascular toxicity, skeletal muscle dysfunction and interruptions in mitochondrial respiration. Microvascular oxygenation responses, measured via near-infrared spectroscopy (NIRS), at peak exercise intensity has previously been associated with aerobic capacity. Specifically, the greater magnitude of microvascular deoxygenation observed at peak exercise intensity has been associated with higher aerobic capacity. Therefore, a pilot study investigated if diagnosis side (uninvolved side, treatment side) and/or exercise side (paddle side, non-paddle side) affected microvascular oxygenation responses at peak intensity during paddle exercise. Thirty-three breast cancer survivors (age = 57 ± 9 years, height = 1.64 ± 0.05 m, weight = 76.5 ± 15.6 kg, 7 ± 7 years since treatment) who also competed as dragon boat racers performed a unilateral (paddle), discontinuous graded exercise test (2-min exercise, 1-min rest) on a rowing ergometer to volitional fatigue. Tissue oxygenation saturation (StO2DIFF ) and total haemoglobin concentration (total[heme]DIFF ) responses at peak exercise intensity were measured bilaterally from the posterior deltoids using NIRS. Two-way analysis of variance determined if diagnosis side and/or exercise side effected StO2DIFF or total[heme]DIFF . Diagnosis side elicited a moderate effect (effect size = 0.66) on StO2DIFF , as the treatment side deoxygenated less (-6.0 ± 14.7 ∆BSL) compared to the uninvolved side (-16.9 ± 16.9 ∆BSL) at peak exercise intensity. No other significant main effects or interactions were observed for StO2DIFF or total[heme]DIFF . The pilot findings suggest that the ability of the exercising muscle to use oxygen for the purpose of mitochondrial oxidative respiration may be impaired on the treatment side.

Acute Effects of 3 Neuromuscular Electrical Stimulation Waveforms on Exercising and Recovery Microvascular Oxygenation Responses.

CONTEXT: When emphasizing muscular strength during postoperative rehabilitation it is recommended to use a neuromuscular electrical stimulation (NMES) waveform that elicits the greatest muscle force and local metabolic demand that is also well tolerated. The present investigation examined the effects that 3 different clinically used NMES waveforms had on the electrically elicited force (EEF), local metabolic demand (exercising muscle oxygen saturation [SmO2]), and the subsequent reactive hyperemia response (recovery total hemoglobin concentration [THb]) of the knee extensors. DESIGN: Single session repeated-measures design. METHODS: EEF, local metabolic demand, and reactive hyperemia responses were measured during and subsequent to 3 NMES waveforms: Russian burst modulated alternating current (RUS), biphasic pulsed current (VMS™), and burst modulated biphasic pulsed current (VMS-Burst™). Exercising SmO2 and recovery THb were assessed noninvasively using a near-infrared spectroscopy sensor placed on the vastus lateralis. Participants completed one set of 10 repetitions of each NMES waveform and were provided with 5 minutes of passive, interset recovery. Two-way, repeated-measures analysis of variance examined if NMES waveform or repetition significantly affected (P < .05) EEF or exercising SmO2. Two-way, repeated-measures analysis of variance examined if NMES waveform or recovery time affected recovery THb. RESULTS: VMS™ and VMS-Burst™ yielded higher EEF (F = 11.839, P < .001) and greater local metabolic stress (lower exercising SmO2, F = 13.654, P < .001) compared with RUS. Greater rate of EEF decline throughout the NMES set was observed during RUS (%Δ = -50 [6] %Rep1) compared with VMS-Burst™ (%Δ = -30 [7] %Rep1) and VMS™ (%Δ = -32 [7] %Rep1). VMS™ elicited a higher reactive hyperemia response (higher recovery THb) compared with RUS (F = 3.427, P = .048). CONCLUSIONS: The present findings support the use of VMS™ or VMS-Burst™ compared with RUS when promoting muscular strength. In addition, the use of VMS™ might provide a greater blood volume to the target muscle subsequent to NMES contractions compared with RUS.

Estimating the Lactate Threshold Using Wireless Near-Infrared Spectroscopy and Threshold Detection Analyses.

The present investigation examined the ability of two threshold detection analyses (maximum distance, Dmax; modified maximum distance, mDmax) in identifying the near-infrared spectroscopy (NIRS) threshold, a lactate threshold (LT) estimate, from exercising tissue oxygen saturation (StO2) responses. Additionally, the test-retest reliability of exercising StO2 and total hemoglobin concentration (THC) responses were examined at moderate and peak cycling intensities. Fourteen healthy, recreationally active participants performed maximal incremental step cycling tests (+25 W / 3 minutes) to volitional fatigue on two separate occasions while StO2 and THC of the vastus lateralis were monitored. Exercising blood [lactate] was collected during Session One. LT and NIRS thresholds (NIRS1, NIRS2) were then determined using Dmax and mDmax threshold analyses. Significant (p < 0.05), moderate correlations were detected between LT and NIRS1 when using Dmax (LT = 130 ± 49 W, NIRS1 = 136 ± 34 W, r = 0.690), but not for mDmax (r = 0.487). No significant test-retest reliability for the NIRS thresholds were observed for Dmax (ICC = 0.351) or mDmax (ICC = 0.385). Exercising StO2 responses demonstrated good reliability (ICC = 0.841-0.873) while exercising THC responses demonstrated moderate-good reliability (ICC = 0.720-0.873) at moderate and peak exercise intensities. The results of this study suggest that neither the Dmax nor mDmax threshold analyses should be used to estimate the LT due to the unreliable detection of the NIRS threshold from session to session.

Acute Neuromuscular and Microvascular Responses to Concentric and Eccentric Exercises With Blood Flow Restriction.

Lauver, JD, Cayot, TE, Rotarius, TR, and Scheuermann, BW. Acute neuromuscular and microvascular responses to concentric and eccentric exercises with blood flow restriction. J Strength Cond Res 34(10): 2725-2733, 2020-The purpose of this study was to investigate the effects of the addition of blood flow restriction (BFR) during concentric and eccentric exercises on muscle excitation and microvascular oxygenation status. Subjects (N = 17) were randomly assigned to either a concentric (CON, CON + BFR) or eccentric (ECC, ECC + BFR) group, with one leg assigned to BFR and the other to non-BFR. Surface electromyography and near-infrared spectroscopy were used to measure muscle excitation and microvascular deoxygenation (deoxy-[Hb + Mb]) and [total hemoglobin concentration] during each condition, respectively. On separate days, subjects completed 4 sets (30, 15, 15, 15) of knee extension exercise at 30% maximal torque, and 1 minute of rest was provided between the sets. Greater excitation of the vastus medialis was observed during CON + BFR (54.4 ± 13.3% maximal voluntary isometric contraction [MVIC]) and ECC + BFR (53.0 ± 18.0% MVIC) compared with CON (42.0 ± 10.8% MVIC) and ECC (46.8 ± 9.6% MVIC). Change in deoxy-[Hb + Mb] was greater during CON + BFR (10.0 ± 10.4 µM) than during CON (4.1 ± 4.0 µM; p < 0.001). ECC + BFR (7.8 ± 6.7 µM) was significantly greater than ECC (3.5 ± 4.7 µM; p = 0.001). Total hemoglobin concentration was greater for ECC + BFR (7.9 ± 4.4 µM) compared with ECC (5.5 ± 3.5 µM). The addition of BFR to eccentric and concentric exercises resulted in a significant increase in metabolic stress and muscle excitation compared with non-BFR exercise. These findings suggest that although BFR may increase the hypertrophic stimulus during both modes of contraction, BFR during concentric contractions may result in a greater stimulus.

The effect of eccentric exercise with blood flow restriction on neuromuscular activation, microvascular oxygenation, and the repeated bout effect.

PURPOSE: To examine the effect of low-intensity eccentric contractions with and without blood flow restriction (BFR) on microvascular oxygenation, neuromuscular activation, and the repeated bout effect (RBE). METHODS: Participants were randomly assigned to either low-intensity (LI), low-intensity with BFR (LI-BFR), or a control (CON) group. Participants in LI and LI-BFR performed a preconditioning bout of low-intensity eccentric exercise prior to about of maximal eccentric exercise. Participants reported 24, 48, 72, and 96 h later to assess muscle damage and function. Surface electromyography (sEMG) and near-infrared spectroscopy (NIRS) were used to measure neuromuscular activation and microvascular deoxygenation (deoxy-[Hb + Mb]) and [total hemoglobin] ([THC]) during the preconditioning bout, respectively. RESULTS: During set-2, LI-BFR resulted in greater activation of the VM-RMS (47.7 ± 11.5% MVIC) compared to LI (67.0 ± 20.0% MVIC), as well as during set-3 (p < 0.05). LI-BFR resulted in a greater change in deoxy-[Hb + Mb] compared to LI during set-2 (LI-BFR 13.1 ± 5.2 µM, LI 6.7 ± 7.9 µM), set-3 (LI-BFR 14.6 ± 6 µM, LI 6.9 ± 7.4 µM), and set-4 (p < 0.05). [THC] was higher during LI-BFR compared to LI (p < 0.05). All groups showed a decrease in MVIC torque immediately after maximal exercise (LI 74.2 ± 14.1%, LI-BFR 75 ± 5.1%, CON 53 ± 18.6%). At 24, 48, 72, and 96 h post maximal eccentric exercise, LI and LI-BFR force deficit was not different from baseline. CONCLUSION: This study suggests that the neuromuscular and deoxygenation (i.e., metabolic stress) responses were considerably different between LI and LI-BFR groups; however, these differences did not lead to improvements in the RBE inferred by performing LI and LI-BFR.

The acute effects of bodyweight suspension exercise on muscle activation and muscular fatigue.

This investigation examined effects of two exercise modes (barbell, BB; bodyweight suspension, BWS) on muscle activation, resistance load, and fatigue. During session one, nine resistance-trained males completed an elbow flexion one-repetition maximum (1RM). During sessions two and three, subjects completed standing biceps curls to fatigue at 70% 1RM utilizing a randomized exercise mode. Surface electromyography (sEMG) recorded muscle activation of the biceps brachii, triceps brachii, anterior deltoid, posterior deltoid, rectus abdominis, and erector spinae. BWS resistance load was measured using a force transducer. Standing maximal voluntary isometric contractions of the elbow flexors recorded at 90° were used to determine the isometric force decrement and rate of fatigue (ROF) during exercise. sEMG and resistance load data were divided into 25% contraction duration bins throughout the concentric phase. BWS resulted in a 67.7 ± 7.4% decline in resistance load throughout the concentric phase (p ≤ 0.05). As a result, BB elicited higher mean resistance loads (31.4 ± 4.0 kg) and biceps brachii sEMG (84.7 ± 27.8% maximal voluntary isometric contractions, MVIC) compared with BWS (20.4 ± 3.4 kg, 63.4 ± 21.6% MVIC). No difference in rectus abdominis or erector spinae sEMG was detected between exercise modes. Isometric force decrement was greater during BWS (-21.7 ± 7.0 kg) compared with BB (-14.9 ± 4.7 kg); however, BB (-3.0 ± 0.8 kg/set) resulted in a steeper decline in ROF compared with BWS (-1.7 ± 0.6 kg/set). The variable resistance loading and greater isometric force decrement observed suggest that select BWS exercises may resemble variable resistance exercise more than previously considered.

Influence of bench angle on upper extremity muscular activation during bench press exercise.

This study compared the muscular activation of the pectoralis major, anterior deltoid and triceps brachii during a free-weight barbell bench press performed at 0°, 30°, 45° and -15° bench angles. Fourteen healthy resistance trained males (age 21.4 ± 0.4 years) participated in this study. One set of six repetitions for each bench press conditions at 65% one repetition maximum were performed. Surface electromyography (sEMG) was utilised to examine the muscular activation of the selected muscles during the eccentric and concentric phases. In addition, each phase was subdivided into 25% contraction durations, resulting in four separate time points for comparison between bench conditions. The sEMG of upper pectoralis displayed no difference during any of the bench conditions when examining the complete concentric contraction, however differences during 26-50% contraction duration were found for both the 30° [122.5 ± 10.1% maximal voluntary isometric contraction (MVIC)] and 45° (124 ± 9.1% MVIC) bench condition, resulting in greater sEMG compared to horizontal (98.2 ± 5.4% MVIC) and -15 (96.1 ± 5.5% MVIC). The sEMG of lower pectoralis was greater during -15° (100.4 ± 5.7% MVIC), 30° (86.6 ± 4.8% MVIC) and horizontal (100.1 ± 5.2% MVIC) bench conditions compared to the 45° (71.9 ± 4.5% MVIC) for the whole concentric contraction. The results of this study support the use of a horizontal bench to achieve muscular activation of both the upper and lower heads of the pectoralis. However, a bench incline angle of 30° or 45° resulted in greater muscular activation during certain time points, suggesting that it is important to consider how muscular activation is affected at various time points when selecting bench press exercises.

Effects of blood flow restriction duration on muscle activation and microvascular oxygenation during low-volume isometric exercise.

The purpose of the investigation was to observe how varying occlusion durations affected neuromuscular activation and microvascular oxygenation during low-volume isometric knee extension exercise. Healthy, recreationally active males performed isometric knee extension at a variety of submaximal intensities under different blood flow restriction (BFR) occlusion durations. The occlusion pressure (130% SBP) was applied either 5 min prior to exercise (PO), immediately prior to exercise (IO) or not during exercise (CON). Surface electromyography (sEMG) and near-infrared spectroscopy (NIRS) was used to record the neuromuscular activation and microvascular oxygenation of the knee extensors during exercise. No difference in sEMG was observed in the vastus lateralis or vastus medialis during any exercise condition or any submaximal intensity. PO elicited greater microvascular deoxygenation (deoxy-[Hb + Mb]) compared to CON (P≤0·05) at all submaximal intensities and also compared to IO at 20% maximal voluntary contraction (MVC). IO resulted in a greater deoxy-[Hb + Mb] response during low-intensity exercise (20% and 40% MVC) compared to CON (P≤0·05). These findings suggest that applying BFR 5 min before exercise can enhance the exercise-induced metabolic stress (i.e. deoxy-[Hb + Mb]), measured via NIRS, during low-intensity exercise (20% MVC) compared to applying BFR immediately prior to exercise. Furthermore, the increased metabolic stress observed during IO is attenuated during high-intensity (60% MVC, 80% MVC) exercise when compared to CON conditions. Knowledge of the changes in exercise-induced metabolic stress between the various occlusion durations may assist in developing efficient BFR exercise programmes.