VO2max test: plateau OR peak?

A true VO2 max is determined only when VO2 plateaus. If you just get a peak value, it's likely you haven't seen the true VO2max of an individual. Fit individuals will be able to reach a plateau or a sustained effort at VOxmax where unfit individuals may not be able to sustain running at or near their maximal oxygen uptake very long. The reason VO2 drops off is simply because your becoming exhausted. Your body has absorbed all the oxygen that it can and so your expired oxygen is going up. Protons build up in blood and muscle thus interfering with neuromuscular functions and your body begins to shut itself down. Your also transporting a lot of CO2 produced from your bodies carbonate buffering system, which is also carried by the same red blood cells that carry oxygen. Your body also really wants to get rid of the CO2 and that's why more oxygen is expired.

Aren't the red blood cells traveling at a faster rate in the bloodstream because of increased HR (due to increased energy demand in the muscles) So wouldn't the reason VO2 begins dropping, regardless of after a plateau or not, is because less oxygen and CO2 can be exchanged due to the decreased time for "delivery"?

But why would some trained runners' VO2s peak and then drop immediately instead of plateauing? Would this indicate a particular weakness at 3k/5k despite success at longer events (10k and up) and a decent mile time? I have seen this occur in other trained distance runners besides myself.

Sometimes it is not so physiological as it is just plain mathematics. Most metabolic carts (the systems that are used to measure expired air volumes and concentrations of expired CO2 and O2) are programed to give you a 1-minute VO2 value based on a briefer period of time of analysis of the data (say a 15-second period of time, for example). If one of those 15-second periods happened to start with an expiration and also end with and expiration, then that 15-second period of time actually has an extra breath in it, and when the computer program multiplies that 15-sec value of expired air by 4 to convert it to a 1-minute value, you now have 4 extra breaths. If each breath is about 3 liters, this means the expired volume of air that is being multiplied times the adjusted FIO2-FEO2 difference (as read by the gas analyzers) will produce a fair bit higher VO2. For example, adding 12 liters to a 150-liter expired air sample results in a 162-liter minute VE. Now multiply both 150 and 162 times a theoretical FIO2-FEO2 difference of .0320 and you get absolute VO2 values of 4800ml and 5184 ml. If you weigh 68 kg, then the relative VO2 values are 70.6 (4800/68)and 76.2 (5184/68)ml/kg, respectively. Now, if the 76.2 value was the one that came out first, followed by the 70.6 value, it sure would appear that you had a peak value that dropped significantly from one minute to the next. Remember, each of those "minute" values are usually not full-minute values, but parts of a minute that have been extrapolated from a much shorter collection time. I may not have use completely realistic values, but hopefuly you get the idea. Anytime a system prints out minute values based on shorter-term collections, you must average several consecutive "minute" values to get the true VO2, and very few labs do this because they tend to believe finding high VO2 values make the lab a better lab, and the computers just automatically print out "max VO2= 76" because that is the highest value sensed by the system. As usual, the computer is just doing what it is programed to do.

Jtupper is right about the sampling and math sometimes being the explanation, but the lack of a plateau in V02 and the actual decrease in VO2 prior to exhaustion are both fairly common events in exercise testing. Some labs use moving averages or other smoothing techniques to minimize these measurment problems and still see a fall in VO2 is some subjects just as you described.

In especially fit runners, the blood will typically desaturate just prior to fatigue, sometimes 10% or more and VO2 uptake will often fall. Various theories have been offered for this phenomenon, but my personal belief is that additional uptake so near exhaustion is not necessarily helpful, and that the human body has evolved to maximize fatigue resistance first and foremost and minimize stress, balancing oxygen dependent and oxygen independent energy supply as needed against the peripheral fatigue and other costs to the system. That is-- oxygen delivery/ uptake is not the top priority in severe exercise. This is more in line w/ Noakes' idea of important muscle and central factors in exercise, the sytem driving the VO2 uptake more than the uptake driving the system.

Another point to consider here I can best explain w/ an anology. If you were to say decide to pack your car up for a trip to the montains, a long hike or a run, you might bring those things out you wish to take on your excursion. As the trunk reaches capacity, however, it might actually work better to bring out fewer items and allow yourself instead some chance to rearrange and pack more efficiently/precisely. You dont want to damage the trunk, nor the items you wish to take. At the end of your efforts,there might be less items getting into the trunk than you mightve hoped for but the end result is that youve done just about as good a job of packing up for your trip as you possibly could, balancing *all* considerations.

Speedster, if you want to read more about challenges to the oxygen centered model of endurance exercise, read Noakes' stuff from about 1992 on. If you want to read about oxygen desaturation, Dempsey is very good.

Thanks for the excellent replies, both Jtupper and dsrunner. I find it interesting that the VO2 peak and decline phenomomen occurs in fit distance runners. In one of my exercise physiology classes, it was taught that this phenomemen only occurs in untrained individuals. But then, in looking at my own VO2max testing data from a study I participated in myself, I questioned this line of thinking.

I don't think I can post spreadsheets on here, so I'm just going to list some of the raw data I have (collected every second) for VO2 towards the later stages of the test. By the way, at this time, my VO2max was determined to be 60.2.

This data shows relative VO2 (body weight taken into account), and these values were taken in couplets of 2 seconds collecting, 1 sec off, from 18:30 to 21:55 (min:sec) of the test.

VO2/Kg Time

ml/min/Kg (min:sec)

57.06816544 (18:30)

57.32381362

58.32005163

58.89400833

57.95189426

58.75806722

59.71127019

58.72571067

57.86419783

57.3731471

57.06866461

56.37027036

57.20446885

56.84794291

58.97448775

58.73898143

58.37039253

58.27061295

57.40489462

57.12915211

58.12126043

57.88227978

52.11734285 (19:02)

55.77620079

55.03968133

55.94743592

52.69686499

60.62219367

58.37539575

56.8381637

56.46082957

58.92484421

57.92978682

57.50902203

58.93402698

57.64983126

59.42461606

58.08284652

56.75901057

57.51256049

58.85425824

57.92464333

59.42637498

60.91664815 (19:30)

60.32405985

60.19174219

60.0407315

59.87919555

60.25791851

60.99016911

58.91160163

61.10276997

60.77106762

59.88918063

60.41055471

61.03318512

58.71098204

59.27592185

59.99149835

59.79058636

60.63505837

61.94598212

59.47447304

59.9135971

60.30298186

59.28301107

58.53942542

59.14259659

59.25223843 (20:02)

57.02799586

58.93583644

60.73948898

61.7383712

61.92347357

63.61529003

61.03169586

60.10703015

61.89108452

60.53905467

60.04184131

60.67455466

59.34082023

57.8778459

58.55272721

57.79331708

58.68115136

59.35674688

59.79234065

59.915475

59.96377421

58.76984495

58.79312578

57.96411881

57.00157632 (20:30)

56.69126603

56.97680519

56.523537

57.37272577

57.7877289

56.68092156

55.04266008

55.42366379

53.52772477

54.85809663

55.44458367

55.95857864

56.11578628

57.16891522

54.89208107

54.85040601

55.83657569

55.3470493

54.7184341

54.86684315

54.85303663

54.58177261

54.16573988

54.09894955

53.99631753

53.37268896

53.8238794

56.06638684

55.91062381

53.55025159 (21:00)

53.96754027

53.877

51.2288505

51.41071653

54.80766717

55.66366192

55.34591885

55.00954993

56.07077818

56.55080239

55.29532255

55.59749457

57.28657383

57.77736079

56.38930216

56.08610298

53.12392391

51.18196827

48.61766669

47.64058932

48.5310892

49.44028351

49.26776176

42.84059104

44.29879028

43.80557288

43.11389043 (21:30)

43.18885196

47.66852823

45.39651681

43.15881976

42.35940985

41.06161338

41.71482224

41.02752576

41.48445789

39.86549822

39.14951748

38.65123849

36.98019544

35.28050974

35.49205076

35.05712429

34.22571205

33.87930824

32.60748192

32.87046579

31.4242612 (21:55)

Looking at this data, the timeframe from reaching peak VO2 to when VO2 began to decline was less than a minute (from 19:30 to 20:30).

After that, I was able to continue running for another 85 seconds until complete exhaustion, terminating the test. All this time, VO2 was decreasing rapidly - from about 60 ml/min/kg to 30 ml/min/kg.

So, when we run at a pace that will cause us to exceed VO2max (like say 10x400 with a short recovery at mile race pace - 110% VO2max ?), is our oxygen uptake decreasing in this manner throughout each repetition? (i.e., starting at a higher value and decreasing rapidly). I wonder how this correlates with lactate levels as well.

bump

J?

After calculating through all the individual readings you provided, your sets of 40 consecutive values give you VO2 numbers of 57.5, 60.2, 56.7 and 50.3 over about a 2-1/2 minute collection time. If you weigh about 65kg and guessing at an STPD VE value of about 130 liters this means your FIO2-FEO2 numbers would go from about .0300 (at the 60.2 VO2) down to .0252 at the 50.3 VO2 (and .0200 when down to a VO2 of 40ml/kg). It would be interesting to see the VE values associated with all these VO2 numbers. It's like you started having a leak in the volume-measuring system, and that a drop in VE is what caused that very large drop in VO2. DO you have the VE data? R values would also be interesting to see.

Thanks, Jtupper. If there was a leak in the system, however, would R continue to increase? I've added the VE and R data below.

VE

(l/min)

116.3207924 (18:31)

116.2010856

117.4122057

117.2074481

117.8640482

119.5983912

119.6408471

119.3818658

118.6538498

119.4243808

119.1028177

119.4243808

118.6219045

122.2285784

122.6137105

122.4000671

123.2518461

122.656106

121.5010706

121.0321094

121.2574614

106.7312347

111.1756676

111.2030601

113.8589766

108.4009378

126.2751952

123.2447613

120.7370779

119.4107439

123.5152899

122.5402708

120.3104063

123.0577891

122.5752624

125.0119768

123.910873

124.8373373

126.433528

127.455508

126.6260783

128.3014532

131.6502627

131.1820415

132.0893799

132.1891702

132.6944217

132.7460647

133.0689587

130.6674452

133.8857535

134.1794496

133.059104

133.4058537

134.5101849

131.4934817

133.059104

135.0473596

135.9562226

135.2291003

137.2873017

134.191096

134.3045991

133.6809818

134.2051744

132.9915661

129.0577777

129.9255634

128.7437665

132.8269667

137.9523783

147.9142334

149.4028526

151.8575176

147.2180055

145.1117137

145.2061004

142.8674194

143.9719553

145.059118

143.6188586

141.4726128

143.0224536

140.2905542

142.490815

143.4362979

145.9227643

145.6790038

147.2007612

147.3396703

148.058374

147.2422377

147.572895

146.3158274

146.5939944

146.9081155

149.3017748

149.9926007

151.8695065

148.6891378

150.4535345

148.7058922

151.336631

151.0366878

154.5396322

152.7564826

155.24863

152.874664

152.0857458

153.0536742

154.4336663

153.0536742

154.1561794

156.9292822

157.4730584

156.7739554

156.6315523

156.7401282

156.2067112

156.9543941

159.9806723

158.4442438

146.8005085

147.3253495

145.2965679

142.1937253

143.6540142

157.4833053

156.785148

157.1309237

159.226733

160.3222463

160.0953071

156.6923087

156.1090895

155.2440666

153.8915592

152.3288298

152.6059852

149.2616801

147.7703267

143.9355829

140.5627789

141.4611271

141.9714046

140.1875159

117.5782648

119.9338627

119.9150258

119.534227

119.4464065

139.1397038

134.9039464

130.6780397

127.4460999

125.0651876

127.9052789

128.8336015

129.7617363

128.6824097

128.7483196

127.5447285

121.7862734

120.8660227

120.8342671

121.7119367

119.9225944

121.7886641

118.5731868

119.2918343

115.290431 (21:55)

R values

1.136971832 (18:31)

1.126401157

1.126474957

1.140221121

1.135170397

1.131777612

1.15423884

1.166818057

1.170103556

1.181991301

1.195578696

1.174531609

1.180441241

1.177448774

1.181419394

1.193005802

1.204795996

1.211668904

1.207099328

1.195083863

1.198496742

1.221026361

1.203746769

1.210913628

1.220247607

1.21746155

1.190192054

1.204963866

1.207274778

1.210028377

1.203894849

1.214660972

1.206818551

1.214823714

1.214659364

1.224951408

1.225159303

1.249330889

1.239235914

1.239295519

1.232133716

1.240359355

1.239486502

1.23709577

1.239885514

1.249141841

1.250765106

1.231493204

1.244626676

1.259366588

1.26618129

1.262254993

1.274690403

1.270716204

1.27430367

1.266594837

1.282216008

1.284480774

1.288663651

1.277611643

1.28123144

1.290256413

1.281916594

1.273955307

1.281816832

1.286116715

1.263615044

1.266607221

1.285987282

1.283123534

1.277324843

1.304973062

1.309858307

1.298607434

1.301030066

1.304565742

1.281086564

1.293744561

1.303176343

1.311422656

1.323372203

1.333868108

1.3356977

1.337544861

1.33295841

1.325277805

1.330651569

1.310650126

1.313633613

1.332521322

1.332119231

1.345964607

1.375400474

1.382785196

1.377200132

1.381245072

1.372699153

1.363484041

1.391147755

1.38190297

1.39679482

1.422813297

1.410271886

1.394179999

1.437815384

1.414202013

1.417964878

1.446355287

1.42898303

1.395654807

1.410559744

1.399131283

1.389615009

1.408716124

1.417122086

1.406695275

1.398669594

1.409821713

1.42009611

1.414553477

1.401244461

1.406273843

1.384675906

1.383802062

1.377691377

1.420142139

1.406503428

1.432523234

1.419644813

1.411632504

1.412984776

1.409457025

1.38250088

1.370233937

1.375478593

1.358000315

1.341963299

1.359896023

1.358457059

1.37354889

1.378889354

1.386429685

1.381215216

1.394746442

1.400377217

1.402007846

1.419050674

1.430632337

1.43259398

1.437122123

1.434186754

1.4386563

1.417994769

1.432116202

1.43360238

1.453809457

1.483494186

1.528516229

1.518101323

1.550093534

1.556821245

1.56027525

1.575490122

1.6376064

1.632708

1.681967767

1.715683915

1.760040066

1.78902615

1.785681268

1.775625354 (21:55)

Something very strange inthese results. Clearly VE dropped toward the end , and that doesn't happen (that I have ever seen). And the R values are extremely high and unrealistic (look more like recovery values in the end). I haven't coppied and calculated the data, but the drop in VO2 sure looks like a good deal of it was associated with a drop in VE. Did you quit breathing at the end? (just kidding). I assume the VE data you list is BTPS (150s would be about 130s STPD and that was my guessed values for VE). Now you need to look at the FEO2 and FECO2 data to see if that changed or was it mostly the VE.

Jtupper, can you post your e-mail address so I can send you the whole Excel spreadsheet of data? I can't make much sense of the FeO2 and FeCO2 data although I'm sure that you will be able to. By the way, I'm pretty confident that the test was performed correctly. I was involved in the dissertation study of Jamey Smogalia (I think he has been in contact with you) and was just looking through some of my raw data that he was kind enough to send me because of my interest.

Jamey Smoliga...spelled his last name wrong the first time

You should read Peter Snell's paper in MSSE (Vol 39 #3).

Thanks for the direction. It appears that their study found that VO2 should simply plateau, even during high intensity efforts over 100% VO2max.

I'm still working on getting the full-text access, so I was only able to skim over the abstract for now. But I look forward to reading through the whole study in the next few days.

your rer values are way off. it appears that the o2 analyzer is not working.

Correction it is MSSE (Vol 39 ISSUE 1)

runfree wrote:

Correction it is MSSE (Vol 39 ISSUE 1)

Correct. Thank you.