Could Chronic EMF Exposure from a Nearby Substation Be Causing the 49ers' Epidemic of Tendon Ruptures?
A deep dive into the non-thermal biological mechanisms from low-frequency AC magnetic fields turning San Francisco's NFL athletes into the league's most fragile.
The San Francisco 49ers are, statistically, the most injured team in the NFL over the past decade, a jarring paradox for a roster widely regarded as one of the league’s most talented.
Note: Readers interested in human health and biological mechanisms: this isn’t an NFL article, it is a deep dive into the non-thermal effects of EMF on connective tissue. The 49ers’ story is simply a compelling real-world case study—stay with me, I promise it will be worth your time.
Since the 2014 move to Levi’s Stadium, they have consistently ranked among the league leaders in adjusted games lost (AGL)—a metric that quantifies the impact of injuries to starters and key players—often placing in the bottom third for health, including dead last in catastrophic years like 2020 and 2024 where their injury burden far exceeded the league average of around 75 AGL. They have also suffered far more full Achilles and patellar tendon ruptures than league average, along with recurrent Grade-3 hamstring and calf tears and high-ankle syndesmosis injuries—tearing the ligaments connecting the shin bones—turned into an annual rite of passage. No other franchise—even those running identical schemes on the same hybrid turf—comes anywhere close.
This constant attrition has likely rewritten the franchise’s trophy room: when relatively healthy, as in 2023 when they ranked among the league’s best in AGL and marched to the Super Bowl with a 12-5 record, the 49ers are nearly unbeatable. In brutally injured years like 2020—when 18 players landed on Injured Reserve, including stars like Nick Bosa and Jimmy Garoppolo—the team plummeted to a losing record despite elite talent.
As of January 5, 2026—the day after a bruising 13-3 loss to the Seahawks that dropped them into the No. 6 wild-card spot—the 49ers’ fragility is once again front and center heading into the playoffs. In that game alone, starting linebackers Dee Winters (ankle) and Tatum Bethune (groin) both left with injuries that make them questionable for the upcoming wild-card matchup, while quarterback Brock Purdy suffered a stinger to his left shoulder on the final play, leaving his status uncertain. These fresh setbacks pile onto a roster already depleted by season-ending injuries to stars like Nick Bosa (torn ACL), Fred Warner (ankle), and Brandon Aiyuk (knee), alongside lingering soft-tissue issues that have plagued the team all year—continuing the lower-body and collagen-rich injury trend that has defined the Levi’s Stadium era.
In early 2025, retired 49ers guard Jon Feliciano let slip a locker-room theory that had circulated among players for years:
“Players have joked around about there being an electrical substation that’s right next to the practice field and how that has led to the Niners’ injury problems.”
What if they weren’t joking?
On December 1, 2025, I walked to the northeast corner of the 49ers’ Marie P. DeBartolo Sports Center practice fields in Santa Clara—a little over 100 yards from Silicon Valley Power’s Mission Substation (the city-owned 60 kV facility that replaced parts of the old Tasman Substation during stadium construction)—and turned on my gaussmeter. At 11:00 a.m. on a quiet Monday (far from peak load), it read 8.5+ milligauss (to put that in perspective, the average background level in a typical American home or office is usually between 0.5 and 3.0 mG). One hundred yards closer, in the facilities where players lift, watch film, and recover, the fields could be several times higher: potentially 13–21 mG on a normal day, spiking even higher during peak grid demand—like evening practices or hot/cold weather when more electricity flows through the substation.
This is chronic, inescapable exposure to extremely low-frequency (ELF) magnetic fields in a biologically active range—and it’s the only major environmental variable unique to the 49ers among NFL teams.
Before diving into the science behind Feliciano’s quip, it’s worth acknowledging the other theories that have swirled around the 49ers’ injury curse. The early Levi’s Stadium turf was notoriously uneven and slippery, causing slips and tears in its first few years, but that was fixed with hybrid grass by 2017, and teams like the Jets and Giants on notoriously bad turf don’t see the same tendon-rupture epidemics. Kyle Shanahan’s aggressive outside-zone scheme demands explosive cuts and maximum effort blocking, which stresses lower bodies, but the Rams under McVay and Dolphins under McDaniel run near-identical plays without the same torrent of injuries.**
These explanations fall short because they’re league-wide realities; none uniquely explain why Santa Clara has become the NFL’s soft-tissue graveyard. Could it be bad luck? Sure, luck always plays a role, but not a decade-long statistical outlier like this. The EMF hypothesis, however, fits like a glove: it’s the one variable no other team faces at this intensity, and the injury pattern—collagen-rich failures in tendons and junctions—matches the exact biological disruptions documented in peer-reviewed research.
The hypothesis itself is simple, but its implications are hard to ignore: these magnetic fields are systematically weakening the players’ collagen, leading to injuries under loads other teams routinely absorb.
Over months and years the structural integrity of the tendons, ligaments, and the critical muscle–tendon junctions is undermined, but the degeneration is subtle enough that it goes unnoticed until a routine cut, block, or plant suddenly ends in a catastrophic snap. The same explosive loads that other teams absorb without incident become season-ending injuries in Santa Clara. And over time, those injuries add up, leaving post-season dreams dashed, year after year. The pattern we’ve documented—decade-long leadership in games lost, the bizarre clustering of snapped Achilles tendons, the endless parade of Grade-3 tears and high-ankle syndesmosis problems—matches the biological fingerprint of prolonged ELF magnetic field exposure with striking precision.
Why This Isn’t on Anyone’s Radar
If anyone at the 49ers—front office, medical staff, or ownership—ever asked PG&E, the county, or a consulting engineer about the big substation next door, the answer would have been exactly the same:
“Perfectly safe. Federal and international guidelines (FCC, ICNIRP, IEEE) only recognize harm from non-ionizing radiation when it causes measurable heating. The magnetic fields you’re measuring are orders of magnitude below those thermal limits, so there is no recognized biological risk.”15
That answer is technically correct under the current rulebook. The problem is the rulebook itself. It still uses the same thermal-only yardstick written in the 1990s, and those guidelines simply ignore non-thermal effects—no matter how many thousands of peer-reviewed studies document them. It’s the same reason cell towers, Wi-Fi routers, and power lines have never been flagged as health hazards. The playbook says “heat or nothing,” so the substation next to the practice fields isn’t even on the checklist.
That’s what everyone has been told, and that’s why no one in charge has ever looked deeper.
The answer, however, lies in a part of physics the guidelines never considered, and it starts with the mitochondria.
To be continued in Part 2: “How Low-Level Electromagnetic Fields Disrupt Mitochondrial Function and Trigger Cellular Dehydration: The Hidden Pathways to Collagen Fragility”
Appendix A — Key Studies & Reviews
ICNIRP/FCC thermal-only paradigm critique
Primary researcher(s): ICBE-EMF <https://ehjournal.biomedcentral.com/articles/10.1186/s12940-022-00900-9>
Appendix B — Injury-Type Index (49ers vs League Baseline, 2014–2025)
Overall Injury Burden (Adjusted Games Lost)
49ers: Consistently Top-5 most injured team (2014–2025)
League Baseline: ~74 AGL/year
49ers Range: ~100–166 AGL/year
Sources:
<https://ftnfantasy.com/nfl/2024-agl-49ers-get-smacked-down-by-injuries>
<https://www.reddit.com/r/nfl/comments/y9bncl/oc_analyzing_adjusted_games_lost_for_the_past/>
Current injury status (as of January 2026): <https://www.espn.com/nfl/team/injuries/_/name/sf/san-francisco-49ers>
Achilles / Patellar Tendon Ruptures
49ers: 7–8 full ruptures since 2014
League Baseline: ~2–3 total per season league-wide (~0.06–0.09 per team per year)
Sources:
Grade-3 Hamstring / Calf Tears
49ers: 40+ major or recurrent tears since 2014
League Baseline: ~12–15 major tears per team per decade
Sources:
High-Ankle Syndesmosis Injuries
49ers: Endemic since 2018
League Baseline: ~90 total per season league-wide
Average Recovery: ~11 weeks
Sources:
*Estimates based on my fence-line measurements at similar urban 115 kV substations in Portland (44–100 mG at ~10–20 ft from bushings/transformers), scaled for Mission’s 60 kV / 150 MVA load and ~50–100 ft distance to buildings/fields (B-field ∝ I / r²). Peak assumes 80–100% load; normal assumes 50–70% midday. The 8.5 mG at the far field edge likely includes contributions from underground 60 kV feeder cables running beneath or near the field to supply the stadium and practice facilities. Buried high-current cables—even when magnetically paired and grounded for cancellation—can produce measurable fields at ground level (typically 5–15 mG directly above the trench, with lateral spread). I measured a 50 mG spike in the street nearby, suggesting a cable run under the roadway; readings dropped off before rising again as I approached the field, indicating additional buried lines or substation bleed.
This strengthens the “inescapable exposure” point: players aren’t just near the substation—they may be training on top of or beside active underground feeders that keep fields elevated across the entire complex (5–15 mG baseline from cables + spikes to 40–60 mG near equipment during load).
Why estimate? The guards did their job and wouldn’t let me enter the facilities for closer readings, and no public data exists—so until that changes, estimating is the best option.
**I should note that I’m only a casual NFL fan—I follow the league loosely and cheer for the 49ers and the Raiders as a Bay Area native, but I’m not a die-hard analyst of schemes, play-calling, and honestly I only even know a fraction of the rules of play. My primary interest here is the human health and biological mechanisms potentially at play.
To that end, I deliberately limited the sourcing and analysis of injury data, play types, scheme comparisons, and the various competing theories (turf quality, coaching style, training volume, etc.) to what was necessary to establish directional accuracy—i.e., to clearly show that the 49ers’ decade-long soft-tissue and tendon injury pattern is a genuine statistical outlier, and that none of the conventional explanations fully account for why it’s so pronounced and persistent in Santa Clara.
If I’ve oversimplified or slightly misstated any football-specific details along the way, I ask for your forgiveness in advance—my goal was never exhaustive sports analysis, but rather to spotlight a compelling real-world pattern that warrants deeper biological scrutiny. I’m always open to corrections, additional sources, or thoughtful counterpoints from those who know the game far better than I do. Feel free to share them in the comments.
Please please please let this be the bombshell we've been hoping for to get the Niners back to SF where they belong. This article is so well researched and makes absolute sense. Teams normally fluctuate with the injury bug but the Niners are consistently the most injured team. This makes absolute sense. Now we need to get the billionaires on board
Hi Peter,
Interesting read and certainly an avenue worth exploring. For context I have a PhD in Biomedical Engineering, with a focus in biomechanics. I spent my PhD studying ligament injuries in sport under one of the top researchers in the US, and have numerous publications in the field. I’d be curious to see the primary sources you are referring to with regard to the actual underlying degradation of the tissue. This is a complex issue to investigate, and likely requires a confluence of animal studies, studies in cell biology, and epidemiological data similar to what you have cited, to gain a clearer perspective. A handful of your pubmed citations led me to 404 error pages, I was wondering if you could provide the name of the paper, or fix the links. I’d like to read them before you release part 2! Thanks for the write up, looking forward to more!