Motor Unit Recruitment and VO
            2
            Responses to All Out Maximal versus Constant Load Exercise Tests

The effects of creatine (Cr) supplementation on cardiovascular, metabolic, and thermoregulatory responses, and on the capacity of trained humans to perform prolonged exercise in the heat was examined. Endurance-trained males (n = 21) performed 2 constant-load exercise tests to exhaustion at 63 ± 5 % VO2max in the heat (ambient temperature: 30.3 ± 0.5 °C) before and after 7 d of Cr (20 g · d–1 ’ Cr + 140 g • d–1 glucose polymer) or placebo. Cr increased intraccl-lular water and reduced thermoregulatory and cardiovascular responses (e.g., heart rate, rectal temperature, sweat rate) but did not significantly increase time to exhaustion (47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P = 0.095). Time to exhaustion was increased significantly in subjects whose estimated intramuscular Cr levels were substantially increased (“responders”: 47.3 ± 4.9 min vs. 51.7 ± 7.4 min, P = 0.031). Cr-induced hyperhydration can result in a more efficient thermoregulatory response during prolonged exercise in the heat.

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Intensity Thresholds and Maximal Lactate Steady State in Small Muscle Group Exercise

Sports ◽

10.3390/sports8060077 ◽

2020 ◽

Vol 8 (6) ◽

pp. 77

Author(s):

Florian Spendier ◽

Alexander Müller ◽

Markus Korinek ◽

Peter Hofmann

Keyword(s):

Steady State ◽

Peak Load ◽

Constant Load ◽

Muscle Group ◽

Group Exercise ◽

Exercise Tests ◽

Three Phase ◽

Load Tests ◽

Small Muscle ◽

Constant Load Exercise

The aim of our study is to determine the first (LTP1) and the second (LTP2) lactate turn points during an incremental bicep curl test and to verify these turn points by ventilatory turn points (VT1 and VT2) and constant-load exercise tests. Twelve subjects performed a one-arm incremental bicep curl exercise (IET) after a one repetition maximum (1RM) test to calculate the step rate for the incremental exercise (1RM/45). Workload was increased every min at a rate of 30 reps/min until maximum. To verify LTPs, VT1 and VT2 were determined from spirometric data, and 30 min constant-load tests (CL) were performed at 5% Pmax below and above turn points. Peak load in IET was 5.3 ± 0.9 kg (Lamax: 2.20 ± 0.40 mmol·L−1; HRmax: 135 ± 15 b·min−1; VO2max: 1.15 ± 0.30 L·min−1). LTP1 was detected at 1.9 ± 0.6 kg (La: 0.86 ± 0.36 mmol·L−1; HR 90 ± 13 b·min−1; VO2: 0.50 ± 0.05 L·min−1) and LTP2 at 3.8 ± 0.7 kg (La: 1.38 ± 0.37 mmol·L−1; 106 ± 10 b·min−1; VO2: 0.62 ± 0.11 L·min−1). Constant-load tests showed a lactate steady-state in all tests except above LTP2, with early termination after 16.5 ± 9.1 min. LTP1 and LTP2 could be determined in IET, which were not significantly different from VT1/VT2. Constant-load exercise validated the three-phase concept, and a steady-state was found at resting values below VT1 and in all other tests except above LTP2. It is suggested that the three-phase model is also applicable to small muscle group exercise.

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Oxygen uptake kinetics during exercise are slowed in patients with peripheral arterial disease

Journal of Applied Physiology ◽

10.1152/jappl.1999.87.2.809 ◽

1999 ◽

Vol 87 (2) ◽

pp. 809-816 ◽

Cited By ~ 57

Author(s):

Timothy A. Bauer ◽

Judith G. Regensteiner ◽

Eric P. Brass ◽

William R. Hiatt

Keyword(s):

Peripheral Arterial Disease ◽

Disease Severity ◽

Smoking Status ◽

Arterial Disease ◽

Constant Load ◽

Oxygen Uptake Kinetics ◽

Peripheral Blood Flow ◽

Exercise Tests ◽

Peripheral Arterial ◽

Constant Load Exercise

Patients with peripheral arterial disease (PAD) have arterial occlusions that limit peripheral blood flow. This study evaluated the dynamic response in O2 consumption (V˙o 2) at the onset of constant-load exercise (V˙o 2kinetics) in patients with PAD. Eight patients with bilateral PAD, seven patients with unilateral PAD, nine age-matched nonsmoking controls, and seven smoking controls performed graded treadmill exercise to assess peak V˙o 2. Subjects also performed constant-load exercise tests at 2.0 miles/h at 0 and 4% grade to determineV˙o 2 kinetics. PeakV˙o 2 was reduced 50% in patients with PAD compared with both control groups ( P < 0.05). At 4% grade, phase 2V˙o 2 kinetics were significantly slowed for the PAD groups compared with controls (60.1 ± 15.7 and 58.7 ± 8.3 s, unilateral and bilateral PAD groups, respectively; compared with 28.4 ± 19.3 and 27.9 ± 8.1 s, nonsmoking and smoking controls, respectively; P < 0.05). No relationship was found between V˙o 2 kinetics and disease severity. These data demonstrate thatV˙o 2 kinetics are markedly slowed in patients with PAD. The impairment inV˙o 2 kinetics is not related to smoking status or arterial disease severity and therefore may reflect altered control of skeletal muscle metabolism.

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