The six-week lull leading up to NFL training camps is nearly over.

For fans, the dead period following the NFL draft and minicamps is one of the most boring times of the year. Pure speculative stories regarding roster movement and position battles emerge as the only form of information for which NFL fans can indulge.

However, the offseason dead period is anything but a break for the players who roam the field on chilly Sundays in the fall. The blood, sweat and tears during the four-month season are only half of their battle.

Offseason training away from team facilities can make the difference between a breakout season and a forgettable one. Talented players can sometimes mask their poor physical shape, but the most consistent players on Sundays are the ones who never take an offseason.

Let’s take a look at a handful of players who push the limits of exhaustion, speed and strength to become impact players on the gridiron.

15. Antonio Brown

Antonio Brown is one of the shiftiest speed receivers in the NFL. Now that his running mate on the opposite side of the field, Mike Wallace, is a resident in South Beach, Brown will have more of a responsibility to carry the Steelers offense.

Brown’s Pilates workout may not look like one of the more intense regimens in the NFL, but I can assure you that the plyometric-based system is far from an easy one. Brown is not the strongest player at his position, but he is certainly more jacked than you or I. The fact that he needs help from his trainer to complete the most simplistic-looking of the exercises is proof enough that he can feel the burn.

Pilates is used to train muscles for quick-twitch movements including cuts and getting out of breaks. It teaches you to have more control of your movements, which is beneficial for Brown’s longevity and quickness.

14. Jamaal Charles

Another former Longhorn and Go Pro representative, Jamaal Charles has had to work very hard after an ACL-injury ended his 2011 season. If it had not been for Adrian Peterson’s miraculous recovery and record-breaking season, there might have been more talk about Charles’ quietly marvelous year as well.

Like Peterson, Charles was less than a year removed from ACL-surgery when he starting a career season. He finished with a career-high 1,509 rushing yards and had nearly 1,750 total yards after adding in 35 receptions.

Plenty of his rehab process was focused on regaining the strength in his knee that made him one of the fastest backs in the NFL. It’s hard to gauge how tough his workout is from the little bit of film shot during the video, but Charles has been able to shake the “slight” identifier that got tagged on him during the draft process in 2008.

Charles has been able up his weight and strength a little bit each season, while not losing his elite speed in the process. The video above shows a preference for free weights and agility drills, which backs up the fact that he withstood almost 300 carries only 11 months after a season-ending injury.

13. Earl Thomas

Earl Thomas is quickly becoming one of the most explosive safeties in the NFL. The former Texas product has accumulated 10 interceptions in his first three seasons, as a part of the feared Seahawks’ defensive backfield.

Thomas backs up his play-making skills with an arsenal of bone-crushing hits over the middle of the field. He spends much of his offseason working on lateral quickness and power to improve his range from his spot as the ‘Hawks last defender.

A self-proclaimed gym rat, Thomas now sells his workout as a part of the Go Pro Workouts network.

12. Drew Brees

Information about Tom Brady or Peyton Manning’s offseason workouts is hard to find, but future Hall of Famer Drew Brees is a different story. Brees uses a combination of traditional and creative exercises with trainer Todd Durkin to get ready for each season.

Brees remains one of the most athletic quarterbacks in the NFL despite turning age 34 right before the Super Bowl. He has also been one of the healthiest quarterbacks in the league since being drafted by the San Diego Chargers in 2001. The Saints’ signal-caller has only missed two starts since the 2004 season and only one missed game coming with New Orleans.

Durkin obviously seems to working the magic because the video above includes fellow stars LaDanian Tomlinson and Aaron Rodgers performing the exercises with Brees. Those three have two NFL and two Super Bowl MVP awards between them.

Something about hitting sledgehammer against a large tire for long periods of time makes me extremely tired.

11. Randall Cobb

Randall Cobb exploded on the scene for the Packers last season, after a rookie year completed with mixed results. Cobb was the only Packers’ receiver to stay healthy for a majority of the season and his production spoke volumes to the amount of work he put in during the offseason.

Cobb’s game relies a lot more on quickness and agility in comparison to speed. His workout recorded by StackVids showcased a number of tough agility and explosiveness drills in conjunction with weights.

Perhaps the most impressive part of his training regimen is doing free-weight exercises while balancing on the BOSU ball. Cobb’s core workouts are now slouch either and for a guy that relies so much on quick cuts to get open, a powerful center of gravity makes him a matchup nightmare for clunky defenders.

10. Dwight Freeney

Dwight Freeney was the latest longtime Indianapolis Colt to leave the Midwest for the AFC West. Freeney landed with San Diego on a two-year deal despite turning 33 and posting the second worst sack total of his career.

Freeney used to rely on a mix of speed and strength, but after 12 years in the league, he has had to learn how to pick his battles. In an interview with The NOC—as seen in the video above—Freeney freely admits that his workouts are no longer about lifting as much as he can.

Instead Freeney spends much of his offseason at his alma mater Syracuse University to do longevity workouts with his college trainer Will Hicks. Freeney will acting as an outside linebacker for the second straight season, after spending the first 11 seasons of his career on the edge of the line.

Due to increased responsibility in coverage, Freeney has had to improve his fluidity of the hips despite increasing in age. He performed okay with the Colts as a linebacker last season, but another full offseason of transition work should benefit the former All-Pro.

His quick sets of weight-based training can put even the strongest young guns to shame and have helped him maintain elite explosiveness from the outset of a play that is unparalleled by few other players.

9. Shawne Merriman

Say what you want about Shawne Merriman’s on-field performance since his steroid involvement, his abilities in the weight room are scary impressive. The now semi-retired Merriman has seen enough ineffectiveness on the field during a few years in Buffalo and decided to pursue the dream of becoming the next American Ninja Warrior.

The ninja warrior competition rewards a special mix of strength, flexibility and quickness. If you have never seen the hour-long specials during off hours on NBC, I encourage you to check it out.

Merriman’s free-weight strength training is chock full of exhausting-looking exercises triggered to workout every part of the body. Merriman looked a little top heavy at the end of his roller coaster career, but there is no doubt that the endless single-armed bench presses with high volumes of weight is impressive.

8. Marcedes Lewis

Marcedes Lewis’ offseason workouts may be one of the toughest around for a guy that is not a high-profile player at his position. Although I suppose we cannot pin Lewis’ lack of production solely on him.

The Jaguars’ tight end spends a bunch of his offseason doing workouts with famed Octagon fighter and “actor” Chuck “The Iceman” Liddell. Joining the retired MMA fighter is NFL FOX insider and mixed martial arts buff Jay Glazer to improve his battle techniques.

Lewis is one of the better duel-functioning tight ends in the league when given the opportunity and mixed martial arts has improved his blocking technique of the years. MMA improves core strength and flexibility, which allows Lewis to make a block early in a play before branching out for a pass.

7. Von Miller

The Denver Broncos’ selection of Von Miller was mildly curious during the 2011 NFL draft considering his pre-draft slotting as a 3-4 outside linebacker. The Broncos ran a 4-3 set, but Miller has transitioned well to the SAM and put up eye-popping sacks in the process.

Miller’s 11.5 sacks in his rookie season earned him AP Defensive Rookie of the Year honors, but his 2012 season was even more impressive. He was half a sack shy of 19 on the season and was recently rated as the ninth best player in the NFL during the NFL Network’s Top 100 segment.

The former Texas A&M product’s early success has been due to a mix of impressive measurables and supreme work ethic. He is another athlete to represent the Go Pro Workout series and displays a few drills designed specifically for young players wanting to play defense.

Miller works a lot with resistance training, from bands to having a four-parachute vest strapped to his chest during sprints. He has also worked really hard to improve his coverage skills, focusing on the backpedaling-to-running drills you see during the combine.

6. Steven Jackson

To play as hard and as long as Steven Jackson does, one has to be doing something right during their time in the weight room. Jackson has switched cities for the upcoming season—trading in his long-time Rams jersey for the Dirty Bird down in Atlanta.

Jackson’s body has taken plenty of shots over the years, but he continues to finish seasons with solid rushing totals. Jackson’s only season in which he did not finish with over 1,000 yards was during his rookie year when he was the backup to Marshall Faulk. He has only missed two games over his last four seasons with the Rams, while averaging nearly 300 carries per season.

His best days are likely over, but Jackson seems determined to extend his nine-year career for just a little while longer. Jackson’s routine is filled with high volume reps of your typical lifting exercises. The first few minutes of his documented workout with STACK shows Jackson’s dedication to top-notch shape with a handful of extreme squats.

5. Tim Tebow

The New England Patriots added well-traveled and beloved quarterback Tim Tebow with much fanfare a month ago—a signing that has been overshadowed by other events. Tebow to New England made oddly-perfect sense after he was released by the New York Jets, but his spot on the team remains a big of an enigma.

Tebow’s oft-talked about career has its fair share of criticism about his abilities to perform as an NFL quarterback. What would be unfair to criticize is Tebow’s work ethic that gives him the opportunity to even stick on an NFL roster.

His dream of becoming an NFL starter may have to take a back seat and his pride swallowed if he wants to continue his playing career in the world’s most famous league. Tebow has shown the willingness to take on any role he is asked and is one of the first guys in the gym.

In case you missed the pre-draft coverage leading up to the 2010 draft, Tebow spent a lot of time working on his mechanics as a quarterback. However, since that time he has looked to get in as pristine shape as he can be.

He spends much of his time at the D1 training facilities and has become an official spokesperson of the growing training franchise over the years. Tebow spends much of his time continuing to work out footwork, but strength drills showcased halfway through the video above display a tireless need to get better.

4. LaRon Landry

LaRon Landry is one of the baddest dudes in the defensive backfield because of his endless supply of hard hits over the middle. He used a rehab year with the Jets in 2012 and turned that into a solid payday with the Colts for the upcoming season.

Landry posted a career-high four forced fumbles in his sixth NFL season and coined the phrase “LARONING” after posting videos of his arduous workouts. Landry’s twitter pictures from last offseason sparked some speculation that he could be taking steroids to get bigger.

His Mark McGwire-sized biceps are hard to ignore and easy to speculate about, but his work put in at the gym is important to note. Landry performs several upper-body exercises in an online video he posted where I’m pretty sure he’s lifting the equivalent to any of the kids from the 90’s flick Heavyweights.

Look up Laroning on YouTube and you'll come across some interesting workout videos. 

3. J.J. Watt

Like Von Miller, J.J. Watt has quickly put fear into the souls of NFL offensive linemen with a ridiculous effort in his sophomore season. J.J. “Swatt,” as he is affectionately called by Houston fans, improved drastically in his second season by adding a new set of swim moves and batted passes at the line.

The first time I saw Watt play at Wisconsin I remember thinking he looked “country strong”—whatever that means. No one was really sure how he would fare in the NFL, but those questions have been quelled after two remarkable seasons, including earning a Defensive Player of the Year award.

Watt’s workout buddies Connor Barwin—now of the Philadelphia Eagles—and Brooks Reed took part in an insane weight program down in Texas last offseason. The workout contained exercises like pushing a 450-pound sled about 50 yards and throwing a 30-pound medicine ball a long distance as if it was a baseball.

NFL offenses should see much of the same from Watt during the 2013 season if this offseason was just as intense.

2. Patrick Willis

Patrick Willis added another All-Pro award to his resume during Willis-like season in 2012. Things have been made even easier for the Ole Miss alum with the addition of Navarro Bowman playing only a few feet away from him.

Willis is proud that he is a self-made professional from a small town in Tennessee. He mentioned in an interview with STACK that his somewhat famous “Homegrown” workout was created because he did not have access to high-priced equipment growing up.

Willis has always played stout against the run, mixing a nose for the football with supreme tackling skills. His simple but intense workout requires multiple reps of medium-heavy weights and a couple hours of rigorous cardio exercises. His physique speaks for itself and the results from the workout have even gotten him a gig as a semi-ferocious villain on a MasterCard commercial.

1. Adrian Peterson

No intense workout list would be complete with the reigning NFL MVP, Adrian Peterson. Peterson was on another planet from his peers this season, only months removed from a devastating knee injury that ended his 2011 season early.

He came within nine yards of breaking the single season rushing record and delivered multiple 200-yard performances with observed ease. A lot of work went into the rehabilitation from the injury and his quick bounce back speaks volumes to the condition of hid body before he tore the ACL.

Peterson’s video game skills do not come without a price though. He spends several hours a day working at the Vikings’ facilities during the offseason to ensure that he is in peak condition for the start of training camp.

His workout changes between upper body and lower body on opposing days, while mixing in plenty of cardio here and there. Hang Cleans, Machine Reverse Flyes and Romanian Deadlifts are all major components of his intense workouts. I don’t know a whole lot about Romanian Deadlifts, but there are always a lot of Romanians on the World’s Strongest Man competitions. It must be pretty intense.

Peterson’s 2012 season was a kind reminder that there is AP and then the rest of the league when it comes to the running back position. Injuries have not always been kind to a player that encourages big hits on his high-running frame, but intense offseason workouts have allowed him to maintain his elite status.